Pragmatic 62: Send It Into The Void Baby

22 March, 2015


John tackles how the internet works - the most requested topic as voted by Pragmatic listeners in this, the penultimate episode of the show.

Transcript available
I bum my wife has bought me some some cappuccino mugs now that fit under the spout properly so I know I've actually made myself cappuccino rather than a mate which is very subtle but still close enough to get and am yes I'm on buzzing on wide at my fingertips are tingling as a minute had too much coffee and here and that might mean you read to wait I think I crossed the line welcome to pragmatic pragmatic is a weekly discussion show concertina practical application of technology exploring the real-world trade-offs with our great ideas are transformed into products and services can change our lives nothing is as simple as it seems this episode is sponsored by is the easy and affordable way to learn we can instantly stream thousands of courses spread by experts in the fields of business software web development graphic design and lots and lots more maybe one master XL are negotiation tactics build a website of Twiggy photoshop skills visit LY to feed your curious mind and get a free 10 day trial there's something for everyone to give ever want to learn something new what are you waiting for this episode pragmatic is also sponsored by safety into pair and the iOS and shopping shopping is a collaborative shopping list at that simple and easy-to-use with great features like pocket locks smart ordering in real-time collaborative updating shopping lists aren't to-do lists and shopping just doesn't just help organise your shopping list items but it also helps you shopping from start to finish it's free on the iOS apps also check it out at safety and pair that SAPI ENT – pair is for more information and will talk about those sponsors will be mourned during the show are on your host John Geagea and I joined today by my coast the cousin has gone back stronger diary going very well thank you arm today we had a holiday short show yes this is very short show that the shorter arm I have never prepared more for an episode I have never arm had a topic that is this arm complicated to cover and it's actually the most highly voted our most popular topic when we have a topic voting up on the site are it was the number one request for fans and seeing as how this is the second last episode of pragmatic it seems only fair as a final arm thank you to the fans of the show that I cover off the most popular topic on the list are and that topic is how the Internet works which is a very broad kind of topic this kind of a lot to it as a lot of pieces so I'm not going to arm under skydiving because let's face it if I get started I'll be here for hours in fact the Robbie will be here hours so strap yourself in for a short show you ready Vic I am ready to do it still man gave so I want to cover the evolution bites of the Internet but I won't take it step-by-step so when the blocks come together that they sort of makes sense there are a few fair warnings at the beginning okay there are lot there are lots of acronyms that I'm grabbing you mentioning this episode don't blame me please blame every other gig in the world invented the stuff and thought acronyms makes things sound cool okay because I know there's a lot acronyms and the stuff I don't get whatever says you short show brace yourself am not going to go down to the voltage level I cannot talk about Manchester encoding and blah blah blah managed in the key points and there are a lot of key points and try help form a clearer picture as to how it works conceptually sonographer talk about plus -5 V signalling organ to about TTL level mocha talk about any of the actual lowest possible level hardware level this voltage this current aerobatic current loop that isn't you can talk about that level because the problem is that honestly I just don't think there's much value in that that said no electrical engineer Malcolm's background of course that stuff is of interest and I could talk about it but I honestly think that let's draw the line in and say were gonna deal with the levels above that so no lower I'm also a little bit every single possible permutation combination of every standard there there was only covering the ones that have historical significance and only covering those are that have influenced where we are to where we are where we are now and how we got where we are now and I think most importantly as well the ones that are currently in use so and mockingly do comparatives arm between different technologies so hopefully by observing those rules will get through this before we all die lovely okay history got start with history so are Leonard Klein Rock at MIT July 1961 he published a paper on packet switching and later a book on the same subject I was 1964 and up until that time data between computers is transferred pretty much our point to point and it was naturally transferred illustrated as serial data stream now the thing as is the case a lot of inventions in a our people say the right rows invented flying loss of staff and the OS draw not I guess I suppose it is true that kind of but there is a bunch of other people work on the same time as was the case with packet data on packet switching concepts on packet switched networks so MIT Rand NPL though all developing very similar packet networking concepts in parallel during the 60s but the name packet was actually coined from NPL's work now guy called time sorry oceans a guy it's a group of people take a bolt or neck and Newman BBN surname of the company a white tender in 1968 to build the first ever interface message processor what we would come to refer to as an ethernet switch so 1968 and the actual first are models of that were used in something called the art and ARPANET was seen to say that wrong ARPANET and that was actually developed and implemented at UCLA in late 1969 so that was really the first recognised computer network using packet switching and what would become ethernet switches now there's a long long history of of ARPANET the people involved I don't want to go into all the details but some key points along the way so NCP are network communications protocol that was the predominant networking standard are on are on the early ARPANET and it managed essentially how the packets were handled and directed through the network so NCP that was the day so there is we have got TCP okay so a guy called Ray Tomlinson wrote the first program to read and send what they originally arm that that the term email wasn't coined until a few years later but electronic mail is that was in 1972 and that was using are the ARPANET so it was first defined TCP to the transmission control protocol was first defined in 1974 are and by 1978 the first form of Internet protocol IP is now we come to call it art was completed the resulting standard was called TCP/IP which is the standard that the Internet is essentially built on now the thing is that despite the fact their standards were in place by the late 70s that while so the statutes and the standards were written drafted and existed implementations took a few more years to sort of trickle out so it wasn't actually until 1983 that the ARPANET and actually switch their entire system to TCP/IP and on the ARPANET at least are NCP had died there were still other fledgling networks around on and so on so forth but these are all isolated networks essentially they started to become more cross connected during the 80s now not going to go into every little detail of all of these ideas note them for the historical significance so 1981 CS net 92 SMTP 93 DNS then we skip forward to 1994 Archie 1991 World Wide Web 993 the Mosaic web browser some key points along the way and yes don't worry undergoing a lot of these later on but I thought it interesting I've obviously before we jump back down the low levels to quickly cover off some of the Internet's based services are services history and what people don't realise is that you because you think about ARPANET the late 70s and think about aren't the 80s and and dad the proliferation of TCP/IP that it was pretty raw stuff there was it was IP address there was like DNS although DNS came round and in the early 883 was the eight implementations of DNS and the widespread usage of it and Internet services built on all this stuff really didn't actually become a thing are like a seminar tuna World Wide Web 1999 only one that's when you start to see some very basic Internet what we would consider an Internet service you start around them so IMDb Internet movie database 1990 it wasn't until 1995 that we got Craig's list we got hammers on got eBay so 19 $0.95 quite a gap that's that's a considerable gap when you think about it arm for if you are considered arm ARPANET switch to TCP/IP compare that to when you got hammers on you was at 13 years are yet 13 years is quite a gap so 996 Hotmail still have a Hotmail account all year younger you have what it you had one did you let it go our my wife still has hers to so it is now owned by Microsoft it became arm micro Windows live and now become our outlook in ochres while this is what Microsoft does hereby something and then branded under the windows/office Monica Wright's letter written alright so ourselves Hotmail 96 998 arm PayPal okay now and then of course the big one Google search Google yes go goal Google so you know 98 was Google time and that's when everything really started to accelerate arm blend Google are nigh at 2001 to 1 we see our best friends are Wikipedia well often well linked and some people say over linked in my show notes but step 2003, got a whole bunch of really good ones then arm Skype which were using right now are MySpace which I think is still alive but mostly dead LinkedIn which is regrettably still alive and I can write the iTunes Store all year and of course a crowd favourite the Pirate Bay 2003 are exactly Moriarty 2004 Facebook or a vertical passbook anyway whatever thousand five U-tube which party makes no money so I had recently whenever 2006 was Twitter and 2008 we get dropbox and specify so there's been a lot of other servers I didn't mention but I thought it was in it was interesting to think about the services that we use today just how far back they go in terms of history and the funny thing for me is that I use Google search every day lower people will say IRU Dr go and I is a notice in his being someone does anyway so all these different people union majority was to his Google search that's actually been around for a very long time allotted by stuff on Amazon so it is more of a North American thing who outside North America answer B and Amazon super because Amazon don't have the you all the benefits of the arm and was on the prime membership was of stuff doesn't have much better benefits in outside the US but you even so it still around's arm now the 20 years that's pretty impressive eBay wanting will tolerate eBay sometimes this ice does not sell stuff on eBay and also did a nice run of use again arm and then I come back two years later and use again to sell something so but I guess never learned whatever arm and IMDb 80s and sometimes soap but anyway interesting though just how far back some stuff doesn't doesn't go but all this stuff is built on the Internet that USENET wouldn't exist so that's what can be built on the Internet a little bit of early history so now let's talk about how it actually does work so hopefully appetites awaited at this point let's get connected with and we got yes let's let's do that okay so let's start with the beginning which is a point-to-point data connection so the concept behind a point-to-point data connection is mindbending the simple it's just a conversation between two people or two devices I raised my hand and say are you ready to get some information on the other person's gonna say yes Simon arose manners are yes ready once I see them raise the handle and ascend a bunch of information continuously and then only given another signal say hey I'm done knowing I got my handle what I do and then they can say they got it once they got by nodding or dropping their hands and yes I got as pretty much it a little bit hand shaking a burst of data and at the end point-to-point serial data communications so not the difference between serial and parallel just note not talking about that serial apparel serial data is just that the data is sent consecutively and with a common spacing and sometimes you have a clock that you then you have some was itself a recovering clock and high-speed serial are or is a parallel clock either way you you clock the data often your strength that I was a paralegal sent Albert Bittle in parallel with a common clock which has also developed problems in I've talked about previously so are not not all about the different serial apparel and talk about arm the basic idea of handshake arm he is a continuous stream of data are not say when it begins today when it ends and you will extracted and then go and do whatever you do it so from a constant conceptual pointer viewed as a basic serial are point-to-point data communication link arm very few layers to it not much not much going on there and that's the way it all began arm one of the evolutions along the way before we arm progressed to the the networking idea of packets and everything are was an idea of a token ring never have a token ring our system after the term you token ring is a sign that I've come across in the arm in automation systems and there's a whole bunch of reasons why token rings are good and is the more reasons why they're bad but anyway so I could settle in process automation come across them some of them are actual genuine token rings are ones are hybrids arm with a modern master slave idea anyway arm but Eliza comes back to guarantee delivery time and start time slots and durations and son so you can come is like Siemens of abuse the system are but they also have their own system or profit in its its overtop of our industrial ethernet which is but a derivative of the ethernet standard but I'm talking about property bus and prognosis of a hybrid token ring system and the idea is think about like you got a bunch of can devices all connected together but each device is connected to the next device in a circle and each of those connections is a point-to-point link just like we said before but yet but like you are the token is like a baton or a talking stick if you'd like your young people argue in big group SA in another talking stick right now you know that's my talk was the era of ever heard that one I mean I have yeah it's just terrible that we've heard about that yet okay so there you can't organiser the talking stick so it's kinda like that though the parcel talking that we were gonna talk about the Tolkien ring is the one Ring to rule them all is the one relying on wanted any health so you is this one doesn't make you disappear it just so she downs anyhow okay token the to device one says here have a token and insight okay I have a token now and no one else's got known as USENET's honour put some data on device one on until device three but to get there ago device to 1st outgoing so I put that are associated data and I pass that on to device to device two has a look at that the data with the token and says this is not for me I shall pass it onto the next bloke passed on to the next one and the next when I was at its device three great I'm the intended recipient and it pulls out the data and does little to do it and it may have a response for device one statement I really like your data or whatever it does who cares point is so I token ring works yet one that has a hardware link listed here sorta kinda kinda sorta yeah yeah it's it's the idea is that arm it's the ultimate in data control you got one person at a time and one person one device at a time and the data gets passed around and there's all sorts of permutations and improvements to the token ring system but honestly it it implementation really can get more complicated but ultimately died because ethernet in some senses it's more complicated but even then in many respects is simpler are and it kind of bits you do ubiquity because of ethernet is inevitable lower lower cost are one out because if if I recall correctly token ring was driven primarily by IBM and Diane ethernet was a bit more open I think that may have been part of it as well but ultimately our packet switching are one token ring still use a lot of automation because it it will give you a guarantee delivery time which is very important process automation you know that you're always getting a response because the token can only sit with you for a certain amount of time before you pass on so that means you guarantee delivery time ways ethernet that is not the case so that it's yet so that means that you essentially have are a bunch of IO out the field and you need to know that input you get data from that that day now that bank of IRA in the field you get that in the next 50 ms of that is important that you get that message in that timeframe so you know it's it's it's important in automation but it's not so important in computer networks where you can have random variable lag piece together packets and resequencing and I reconstruct the data in your good so Yates not yet anyway so ultimately ethernet are ethernet one out of a token ring such thuggery still exists but it's very very violence does not popular so anyway okay so before we are talk about arm ethernet networks and and so and so forth I think it was it's helpful to talk about another point-to-point link are and that is the essentially in the beginning computers personal computers particular spokesman for second personal computers were didn't have a network card because you note you will need ethernet for you even though when no Vic 20 existed our networks existed and is arm you the original coaxial network site 10 base fireman's honour all those things existed that you networking computers with a while to do that no it was something that only universities will do that had not lots of data sharing home home computers had there was no Internet really to connect to you to dial in perhaps I guess modems that exist with our point-to-point links say you had BBSs knows other bits and bobs not really can talk about the point is that you computers have no network interface cards the way you would connect to anything are you on the Internet when the Internet came about really arm that was so through a modem and motives would connect to your device your computer are usually by serial port usually was RS 232 eventually that the other summer connect through parallel ports but generally speaking our adventure that they became USB but by the time that was happening everything was moving towards ethernet and yellow again towards Wi-Fi router is on you to where we are today so in the beginning no longer said my mind the first computer in our household of the 20 had the networking capability at all and are our first PC had a dial-up modem and it was a yarn of Jesus was a 19.2 K are dial-up modem and our blazing hours blazing fast all year are lovers those using compression man in here so are CF and a lot of early our companies and users just didn't see the Internet as being useful in their seems crazy now but going thinking back in a Ross I said shrug Internet was the big deal and think about you back then in this low alto map like the late 80s early 90s seed by you compactly gateway we whatever the hell any you have only to dial dial into an Internet into the Internet that there was much out there you will Woody what is there out there on Internet you had horrible search engines you know that didn't find very much as was much defined the majority of people use and were you research in universities you the average person with a personal computer home had no real use for it so it didn't become are you all that useful and I think that a lot of that a lot of problems were that some the data rates so the data rates start having very slight I get going back to the problem with this conversation is that it's hard to know where to start so imagining myself a computer you gotta use a dial-up modem how do you connect you need an Internet service provider and Internet service providers you… Go back to America Online for example and there were hundreds of thousands of ISPs in your dial into them did they give your phone number you would dial in and you would connect after they are modems and negotiate our and they were ground speed and then you would be connected to their network and their the ISPs are location was then connected through switches to the Internet will talk about how later the point is that at dial-up connection was done over a phone line and yet that's because that's all we had there were no mobile phones you ADSL hadn't really been invented that point I mean nothing theoretically perhaps but you know the whole asynchronous your digital subscriber line concepts and that the filtering and everything that existed it was just a an analog phone line through an analog telephone exchange God knows how many telephone exchange as you pass through between your house and the Internet service provider could be a must either side of town you know you don't know and expect to be very telephone exchange between you know all analog you know so that was what you're up against so the amount of noise you analog noise and most finalises terrible just terrible know so that's why these modems are start out really low bit rates because they had operated high noise environments so stable 1220 400 board you board you bits per second right and then when things started to Excelerator 9600 board IO others per point in the August of 19.6 kilobits kilobits per second killer boards IN our talking and I said in our first one was 19.2 K I mean either TMC modem you for far amateur radio that was 1200 board so but that's their story and what automatic sets packet radio and no one did packet radio hardly anyone did comparatively speaking so let's not worry about that so what changed though is that some of the backend improved more information from more people saw them seeing the benefit of the Internet was added all around the world and suddenly become a more interesting place to be some more demand meant that they need to be faster ways to connect get more this data and that led to more ideas well there was a proliferation at that time for a bunch of other efficiency reasons away from analog exchanges to digital exchanges ones where all the circuits which was done digitally and it started out in the back in the high density yellow switching between exchanges are and then eventually moved its way out into the suburbs so that your Suburban telephone exchanges were essentially just AER and analog line from the nearest telephone exchange to your home and that was it everything else was digital so soon as it came in a telephone exchange was digitised and away you go so that meant it was then possible to start mounting our essentially Internet specific equipment at the actual telephone exchanges and that allowed are that allowed the ER in its service providers to say okay well now we can cut out all the switching loss in all this other analog to digital losses we can actually arm just you use this last but the site they caught the last mile right it's not it's not mile you at the last kilometre if you call us, whatever you it what it means is it's the distance from the telephone exchange to your house and whatever distances it could be you hundred feet it could be 10,000 feet over not 10,000 feet long way but you know it could be a long way and that the point was that because you only dealing that last bit it cuts down the amount of noise that the phoneline can pick up significantly and it allows you to use ADSL so we start out with ADSL one then that progress to Newstead ADSL to the nasal 2+ ever goes and says ISL 2+ yet is fantastic and get tens of megabits per second and is like yeah that's great provided your living next to the dam telephone exchange is more than a few hundred feet feel way good luck so in a problem that is of course that aren't there is only so much data you can push down a twisted pair cable over a significant distance and the reason why this is straightforward enough and that is that our digital information on off lidar voltage goes on voltages of cargoes on cargoes of all those switching transience are governed by inductance and capacitance in the cable.the larger the inductance/capacitance the more difficult it is those pulses that actually maintain their shape by the time they get the other end of the further you go down the more capacitance inductive effect therefore the more shut more more rounded the edges become the more difficult it is to detect whether or not that is actually a one or a zero and that is a gross over certification I'm excluding quadratic modulation on I'm so amounting to Matt QPSK Noah McGuinness all the other stuff in different modulation methods and so and so forth that's the basic idea capacitance inductance is your enemy because the transmission lines that were laid down were never intended for the digital information are intended for an analog phone call and I do that job just fine so we covered ADSL harbour out there in the telephone exchanges and then people can connect with ADSL modem instead of a dial-up modem and that means that you're always connected because not the dialling to connect to your always connected senior dialling instrument of exchange any more technically you're going to our essentially superimposing digital information of the topic analog phone line it only goes the exchange and then that digital information strip off and sent digitally through the backbones back to the ISP so you cutting out all that noise but same time there is still limitations how fast you can go so obviously there's also cable modems and nowadays we have fibrotic survival of his digital all the way but most people do not have fibrotic into their homes and are you globally speaking certainly not now concerning on my country and frankly certainly not even in the United States it is becoming more common but I mean I do not the statistics are by guarantee the vast majority of homes do not have ideas another number is actually but there had been arrested two I'd I'd guess that most of it most of the people are connected in this country via cable modem or DSL yet exactly right and it's not the same as the case here and some people are unfortunate enough to have to deal satellite and all the lag that goes with that and then and live them at sites that so the more modern approach has been to utilise are the cellular networks so where are our weather is no a no analog phone connection which you can potentially ADSL and are in is no cable because you not ever get cable you can just use a 3G network the 4G network 11 on LTE you that's pretty damn desperate scream and fast because the problem that is it's a shared network of shared data shared them medium which means that the ADSL dial-up are cable modems all those things are dedicated connection between the exchange and you were as 3G and 4G is shared by anyone who can speak to that that mobile phone tower/vector in the cell that you're talking on so that means that it's not just you using that is why you are as down to luck so no pending hard disk do you feel lucky anyhow I really don't do a very good clinics with cyber yet mechanical right so during this transition where speeds and are on at the client connection start to evolve something else happens as the bandwidth increases the amount of information available Internet increases more devices because the average cost devices in the home is reducing so no longer is it do you have a computer in your household in the 80s and you be young one in 10 people maybe with a hand up do you have a computer house on the 90s to all 345 people with a hands up now where the noughts the 2000s is in last decade having people have one computer in a house every hand goes up amicably by 23 to 4 computers in the house more hands go up in I say so suddenly it is no longer just about a point-to-point link it's about okay I have one phone line into this house I got one Internet connection this house but I got multiple devices how do I deal with this problem so that's when the proliferation of home private networks started to happen and modems cease to be just modems and they had to evolve by implementing another functionality existed in enterprise networks for quite some time that rousing before we talk about rousing know it is important also to discreetly mention that some operating system supported Internet connection sharing so you can have a dial-up modem connected to your your computer which would be your Internet connected computer and then what you do is you'd share your Internet connection with the computers on your network and they would quote unquote automatically figure it out some of them were less automatic than others are not naming names Windows but I had problems and your problems became my problems and enough said so yeah I was really glad that Internet connection sharing died and was replaced by genuine router because let's face it around actually works far more reliably so there you and good luck with the Internet connection sharing no I don't think any people did he sorta kinda occasionally worked but in a was pain in the neck and because the problem was it live a computer on all the time so if you want other neck of his network then your Internet connection connected sharing computer had to be on and awake couldn't go to sleep and also the rubbish is a pain in the neck so thankfully are modems evolved and they then started to incorporate rounding functionality and allows multiple devices to access the same Internet connection because the motor was always on so by incorporating a router into the modem all the computers then connect to the router/modem and that gives them all access to the same Internet connection survey men share that in that connection to everyone's happy well until because you have young kids and the kids up all the bandwidth and are left with nothing came of Scott phone call and that such a first will problem but anyhow okay with me so far here you here now and again that imply that you with me so far it fantastic okay her AAA so scratch the surface here summons to cover okay so do do do do do do ISPs are essentially then provide you that point-to-point connection are into your house and then once it's in your house you have an Internet connection of some kind and of course traditionally it was a wired ethernet connection rather however more often than not these days it's now Wi-Fi wireless are ethernet connection and you have your own little private network in your house and your urinal private party so once once your motor morale has connect the ISPs network they then wrap your pack as to wherever they may need to go however are there is one other thing talk about on ISPs before we are with fully change the subject and I say change the subject it's all the same subject which I mean same sub- sub- subject is some subject to word ISPs one of the problems is they have a bank of IP addresses that they have to doll out to people that connect to their system I am a fixed number selected to manage them carefully and overly miserly about to give some kind of a rationale reason so as to flavours there is the fixed IP which everyone says they wants but they are properly need and there's the dynamic IP addresses is pretty simple fixed IP means on the login as me John Geagea to the ISP and SAI John is your IP same as always hope you happy giving extra 10 bucks a month since I Pretty much the business has 10 bucks to inquire as to fixed IP anyway dynamic one says hi giants you yeah is used in Genie cheap to keep 10 bucks a month and you I get that same IP address was that it still the same as last week now whatever maybe it won't be the maybe will be says go big bucket that is pick whatever number one Allah bucket that reuse of IP addresses that the dynamic method meant that the ISPs can allocate whatever they like to you from a pool and it's just easier and more efficient theoretically and perhaps it's more of a tradition thing honestly I feel like the days of dynamic IP addresses are kinder over to an extent because if you think about it makes sense and a lot of people connecting and disconnecting all the time it was always on key Internet connections and my ADSL is always connected unless causing a power goes out or the modem dies or samples out the cable from the back of the modem or insert reason here that is not a common occurrence generally speaking I connect to my ISP and I'm gonna have the same connection up for days weeks maybe even months that they. Max capacity is can become a de facto fixed IP anyway exactly so my pool as as as more and is a larger percentage or proportion thing about of my of my dynamic pool become always on connections it's easy to become a dynamic pool can be reused you know all becomes a highly defragmented pool of IP addresses of which there is very little point in reusing them so you know it's I find it it's when you dial-up's a dial-up modem it made absolutely great sense when you had a handful of people like him for but a relatively small proportion of people with with that with are always on Internet connections I think it made sense but I'm big I think it is making less and less sense these days and I really don't you know when I get off charging 10 bucks a month extra for a fixed IP address so even if you had a dynamic IP address and just by the way for the record I have a dynamic IP address is stingy no actually although maybe I am stingy but the point is I don't need one I know I don't need so for a very long time there are a bunch of services there around the could get help your round this problem may be a herd of one of of 1 to 11 imagine what I used to use that was the IN DNS her them are I think the area do you IN DNS short the dynamic DNS stealth are you so Isaiah that was filled with yes so did. They are hardly Web server several years back and that both were used to negotiate cool yes so am I is the IN DNS arm for quite a while and it was a free service for quite a while but like so many free services they realised how we can make money from this and cease to be a free service me I can always pay nominal amount but I stopped needing and I stopped bothering with and as a harbinger reasons why which we will get to later on the upside don't worry but the moment let's assume that you have to have an publicly known externally externally are available IP address in order for you to essentially connect back into your home system when you're out and about that would be useful IP address if you're running a Web server of your home computer which is highly inadvisable but you know you can if you really want to then you would need and I fixed a static IP address but if you don't want pay for one what you want Indian STDs you would point your modem modem router are to the DUI in DNS service you have given your login credentials and what will happen is every time you log in the ISP was sent a message to DUI in DNS saying hey he is the IP address that my ISP has assigned to me and then the IN DNS would give you essentially you could then connect that to a domain and you could say right on again this domain and it will simply to redirect you to the IP address that was dynamically allocated to you by ISP may presto I have a quote unquote fixed dish kinda sorta fixed dish IP address so that was that while the ways around it and there are other ways but that was one way and are you so if you want to get the answers to your laptop from home using the Back to My Mac or different BMC software like maybe like screens then see your teleport or is much different ones our dentists two examples is plenty you sigh are not cited FTP OR real BMC tightly and see Lucy and see whatever anyway arm yeah that's that the Lego but the bottom line is that the downside I was your line of third-party service to provide access and eventually the way in DNS got got got wise got smart and I got greedy now propping up labour rewrite and money to sustain their existence that's fine as is that I didn't need a service that much because I found another way which will talk about later if sold the dynamic problem as it was the Lego sets a bit about ISPs and that last mile connection nor can I go to to much more detail about that and the reason not because there is so much more still to talk about but before we do like to benefit sponsor and that is is the problem solvers the curious and people who want to make things happen you can instantly stream thousands of courses credible experts in their fields of business software when devolving graphic design audio and lots and lots more weight me list here now they have an enormous library you might even say gargantuan of titles that you can choose from with new courses at each and every day that make sure the library is relevant and 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try and once you do your see exactly what I'm about and why think it's a good thank you once again to for sponsoring pragmatic okay next let's talk about the stack was when you say what stack is given top of the the stereo cakes the pancakes that great will it let left let's go back to the bush or a daily reading and restorative were not restarting a no no no no that was not terribly bad joke I don't care long stack short stack medium stack TCP/IP stack was worse than my usual was the new there is no worse than usual TCP/IP stack yet I'll now then cats better and okay so TCP/IP stack so we talked before about development TCP/IP and I was in the early A arm late 70s sorry and the mentation up and around 93 when I switched TCP/IP and it is the standard that we continue to use today however there is a model arm that she may have come across called the OSI model in the OSI model are is a very handy way of thinking about our different layers of the Internet has lots of references the outside model but technically TCP/IP does not have as many layers of the Oslo model has seven layers the TCP/IP layer combined some of those to have four layers but it's intentionally less rigid which is why TCP/IP I think generally it's accepted because it is less rigid is far more popular arm to describe in these terms only one not talked much about the OSI model reference and soul only reference that whereas relevant sticking with TCP/IP the four layers in TCP/IP layer stack are the application layer the transport layer the network layer and the data link layer so what the hell does that mean a layer in stack refers to the set of protocols that are used whether they are hardware or firmware or software whatever you think how you think about those different layers control how data is handled and what I handled it could be the lowest level of you what voltage this is are indicating what this is what what one is what is zero is are all the way up to you this application is requesting ASCII character whatever from this site and it's encapsulated in a packet that packet switched through fibreglass so every layer of those more of them of the TCP/IP stack has a specific purpose so I talk about each of those layers in turn are so will start top and work our way down to the very top layer and are the application layer TCP/IP is actually the amalgamation of three separate layers in the ISI model to the outside model starts without the application layer at the top then calls a presentation layer and a session layer been TCP/IP by Hezbollah together and call out the application layer and the reason they do I think is because session and presentation are all essentially subsets of an application and was an application layer onto amount out that the protocols are that operators layer ones that were all familiar white think Moses of me with a HTTP Hypertext transfer protocol FTP file transfer protocol SMTP which is the simple mail transfer protocol and SNMP simple network Management protocol and I did warn you that there are a lot of acronyms and that the ego so transport layer next one down essentially the transport layer has two primary protocols and this is where we mention our good friend TCP the transmission control protocol there's another one UDP which is the user datagram datagram protocol saw that protocols yell so TCP what does it take the data from the application layer and break it down into the corner quote correct sized pieces but it planning the release of those pieces onto the network it has the acknowledgement of receipt packets and manages reasons of lost packets of this timeouts for said centre packets now UDP on the other hand is a bit more streamlined by streamlined I mean careless and my cows I mean hedges doesn't care quite as much and as the way to think about because it doesn't really take any measures to ensure the datacentre is actually received by the target hosted site set into the void baby see you later now predominantly it's useful for lower band with lower priority tasks like streaming audio and video you including Skype and VoIP you wear if you lose a small number of packets of data you still gonna be able to figure out what's going on minute now the discerning person would say I need every last bit or it's just not right or something I know what people like that white savoured that my they may say that our anyway so yet UDP is generally frowned upon friending other than streaming there's probably other applications for but that's the most common that I'm aware of okay network layer are also referred to as the Internet layer and that's how packets are actually routed around the network figuring out how to reach the correct destination that then of course there's the data link layer and it's also referred to as the network interface layer but in the OSI model is actually two separate layers the data link layer again they say name but also the physical layer and the physical layer is literally the voltage level so voltage this current that lovable are now the reason I think that the TCP/IP model is better is because it again it can combines those levels of the outside model that make the most sense because they normally get grouped together because ordinarily the physical late in the datalink layer are are combined anyway okay so the basic structure of the data as well as the voltages kinda go hand-in-hand in terms of their mentation so I think that makes sense so those are the basic four groups and a little bit about each of them so now it's time to talk about the datalink layer of ethernet which is essentially the building block of all networking that that the Internet is built on the datalink layer the datalink layer level the level linking Levelland of the datalink lots of elves okay so in the OSI arm context the physical layer of ethernet didn't's start out as those pretty blue is a pretty while the blue anyway ethernet cables we think of today those CAT5 patch leads whatever you are: it actually started out as black typically coaxial cable have you ever seen a coaxial cable ethernet network that I have and how it strike you are well aside from the connector only and it looks like any other coaxial cable that was a cool arm did you walk up to it and say man that some pretty cool coaxial got their AAAA lyric of the game or that looks much easier to connect than the way we have the screw that thing on the back of the TV you now I'll admit first coaxial arm ethernet network I saw at uni are ITS what struck me about it was our how shiny it was because the past that you could see the majority of where the kayaks would come out of the cable duct are out the back of the computer are going to shiny teepees and then out this ITP sometimes into a bus terminator all that was a shiny silver either BNC connectors on a teepees or BNC connector in the back of the computer network interface card it was all shiny cycling shorts all that thought let's call and a) allegorically she had a very sparkly and back in the days when I was still learning about how the staff worked every now and then I be like all this in bit the terminator December comes off cool taken off all that looks cool in an down the other end of row computers people say hey Yum something has happened my data transfer might are quickly and surreptitiously put them back on again whips so that they can frown on that what's the deal anyhow bottom-line thanking Atlantis arm so that anyhow so yes are iconic in my summit so giveaway giveaway note really talked about the pros can talk about was down. I was BNC connectors are BNC is as a kind of connector it's very typically using coaxial cable the funny thing is that the kayaks of They used it was a typical use 50 ohm kayaks and the best part about 50 ohm currencies that's just the same kind kayaks that use an CB radio and on them and now an amateur radio for rough radio applications are semi 5 ohm is actually far more common are back in the days of the television coaxial cable I guess some TV stories coaxial cables are 75 and was the Stanford TVs rubbish different reasons and ultimately along to 300 ohm and that's balance and is unbalanced in mind that so the attractions of coaxial cable why they start with car wax any ideas suggestions thoughts comments are right fair enough and it's made it's obvious made it's not me I guess I made amendments to long and I think everything is obvious and probably isn't it you that the bottom line is that coaxial cable if you do a cross-section of kayaks what you got your score a semiconductor you got what they call dielectric and dielectric is just an insider so fancy name for insulator mud dielectric in the middle yell and I know why keeping an accent just feels cool and maybe only to upgrade my accent and I have either too much coffee that is my problem may be that sorry it felt its orbit ankle figured so are right yes and then outside that you have a shield and a shield can know is most often a flexible grade are depending on the grade of the coaxial cable sometimes you'll have a ADR foil are over the top of that and then you'll have an outer protective sheath and that will be another insulator the idea is that your centre conductor is heavily shielded and heavily protected which makes it very quiet not just that the dielectric is are essentially such a good insulator are in such a good dinner and it's such a it's such a uniform spacing between the sheath and shield and the semiconductor has a very highly controlled characteristic impedance and the one thing is really important transmission lines efficiency is having a consistent are characteristic impedance of 50 ohms is all that means is that you can model the characteristics of that line and that means that in theory at least you can get more data same theory however the arm ultimate solution is that we didn't use coaxial cables we got a twisted pair why get that is the second first-ever coaxial ethernet was actually called 10 base five and used RGS 8X kayaks and its rather thick not particularly flexible proper good for whipping people with that pretty sinister idea and is expensive so those reasons are actually was referred to as thick ethernet these days everything views that following that in the mid-80s came then ethernet some people call it the net but technically 10 base to that used much cheaper RG 58 cable and I used a bucket load of that not that I ever caught up in a bucket but anyway I used a fair amount of it and down out that my early radio days in CB radios RG 58 duster for the win so still however dealing with 10 Mb per second transfer rate and that's where 10 base five start has the tender beginning right that was the amalgamated data transfer rate 10 Mb that's so fast meant blistering speed okay now at this point in time all the coaxial cables connected together the back of all network interface controllers so what's the one obvious observation from connecting all the computers to a coaxial cable and joining them all together in one long bus the conclusion is a traffic jam pretty much cheer your situation it really isn't all that much better than what we have now with 3G and 4G have referred me laments in the past the problem are with the rising oldest now add more data are Wi-Fi more than a Wi-Fi site while eventually overrun our band with guys you run a radio spectrum it's gonna be a problem okay when people like to believe it or not it is absolutely going to happen however if you can contain all that inside a cage of sorts like coaxial cable that's great but the problem is if you put every computer was the talk on the same bit of coaxial cable the same bus you got yourself a problem so ultimately our it was not technically a point-to-point link it was an ethernet bus capital okay however in 1984 a little company called American telephone and telegraph that the AT&T they created something called style land which was way ahead of its time as a way ahead in a few years but still ahead of its time and use far cheaper twisted pair cable in all his carry the data around in well you guess it as the name suggests a start apology as opposed to a blast apology as amazing as it was never took off factors complete failure and collapse and no one ever really used it shown that but the concept and the ideas behind it essentially drove pretty much all the future wide local ethernet networks and that's what we use essentially today the bit rates originally were pretty ordinary and maybe this is why the reasons why it failed 1 Mb per second mean really that's like 1/10 the speed of that thick net or even for net no innocent then that I want this style land rubbish and making him the second Charlotte okay so it wasn't actually until 10 base TENS on the run think that remembers 10 BaseT that came in in early 90s so when I went to uni in 1993 thing was, memories hazy anyway the PC ladder still connected by coaxial but within one year they'd all switched over to 10 BaseT why it was easier it was simpler it was cheaper easy to install it was just it was better it only has it had the same speed but of course because the architecture it had about effective throughput was on the bus and email so are well it wasn't wasn't it had the capacity to not be a bison to that later so 10 BaseT are originally used Three are which people don't remember being right are the far more popular stand however was called category five and that category five cable hard essentially is a four pair unshielded cable uses an eight PHC modular connector however of intellect in telephony is to say our telephone telecommunications the eight PHC is referred to by another designation the most people refer to our more familiar with and that is RJ 45 to the RJ 45 connector and the cat five cable are big as become ubiquitous with wired ethernet connectivity and has done since the early 90s so the early standards 10 BaseT are defined different modes of operation full duplex half duplex and order negotiation for originally of course 10 BaseT then hundred BaseT and more recent systems are gigabit 1000 BaseT are not talked much about all the order negotiation full duplex afterplay selects identical and interesting but you know it there's clearly some show notes if you'd like to arm and on Ella another honour sort of a sub note about the amount of notes in the show notes this episode there is a metric ton metric even imperial ton does matter is a lot of stuff on the Internet about the Internet so there is no shortage of information out there about this to everyone about full duplex heart duplex order negotiation and that low level go for it plenty read arm anyway while the other extinct things is that cross that that some 10 100 Dar BaseT only use two pairs actually in a stand cat five cable and are the pens that they present honour pins 1 to 3 and six the other two are actually used instead installations and the people be an really stingy many many years ago there are actually patch cables it came out that only had two pairs in them are because it was cheaper right and the super cheap ones are they say our hottest plug this into my arm my awesome IP phone and you put in your IP phone with dead and be like knock knock on the phone yeah why you're not working outside of our it needs power over ethernet and the power of reason that uses the other pairs are psychotic gonna upgrade to a real ethernet cable so yet beginners mistake during the transition period but eventually of course the likening mass produced they made so many of these damp Ashley Jintao pick up anywhere you like my price probably gone MS why hearing in a stray dirt cheap Gaelic remarks to boxing and live media cat five patch leaders like insane this thing is a mass produced by the metric ton there I go again imperial ton every doesn't matter a ton is still a lot so I tonnage okay gigabit however you saw four pairs and it also requires a higher quality of cable with tighter tolerances and they specify that you will stay suggest that you use our category 5E which is a far tighter tolerance now despite this irrespective of the kind of cable that you use the amount of inductance and capacitance you get the twisted pair is the same problem with phone lines exist in a small scale and you pushing more data think about a mean ADSL maximum data and 80 cell 2+ is what 4060 Mb per second were try to push hundred and gigabit per second obvious that you have arranged limitation obviously the capacitance is gonna kill it so what happens hundred metres is typically we get that's fine because that's all you've got me imagine how many houses have you got that require more than 100 m for point-to-point connection not many that I can think of unless you are a mansion or make mention of settlement mansions connected by Mick Mansion corridor I don't know why I mean I know you have a big mountain did not mention is I do not have a Mick Mansion and in an automatic Mansion and maybe possibly imagine held by somebody that owns McDonald's now it's a strain express I didn't think it was that the idea of a mansion is that a mansion is like really really big and expensive and luxurious and usually has two flaws in its huge amount of rooms most unnecessary most the mind unused requires arm dedicated full-time cleaning because it's a ridiculously oversize design of opulence and wealth and all other gases not that naked argue in a capitalist economy is good thing that most people look at that shake their head saying whatever and how AER a normal house is like what you and I live in its house with a normal number of rooms that are all got stuff in them somewhat so too much stuff specially in my house stuff to me stuffed toys and kids rooms anyway after a Mick Mansion somewhere between you got enough money to arm psych and Anna usually are like a Mick Mansion psycho and it's more a cookie-cutter field because mansions are typically very highly customised was a Mick Mansion is is is still built by a reputable company but double lots of them is only a limited number of floorplans in NASA and South McDonald's Mick Mansion and that Liz is my understanding the entomology I've done no research on that one so the go could be wrong ask Wikipedia okay so it's also not related to a Scrooge bin this is not illegal alien ladder yes we have indeed clarification has been sought okay good lovely charming however if you use high-quality cables it is possible that you can push 250 m but high speeds are guaranteed you cross 100 m limit you on your own now there were some cases I've done installations where what we what we did is we Ashley put AER a ethernet switch are at roughly the Hundred hundred and 10 m point cited some factory automation back 10 years ago where we had a 10 100 link that we want to get from one of the factory to the other total length the factory was around about 100 and 8090 m so the computer they had in the office at the front of the warehouse was actually communicating with a plc down the back end of the war the warehouse connect the machines although I do is have a look at what she was doing but they won't do that from the beautiful air-conditioned comfort of the shopfront and I did say to their customers coming in I look he is a machine making widgets and customer come and look at the screen so it will look it's pretty widgets lovely anyway so not to make this work arm you open ethernet switching between and dark as the other good news was that there was AER a GPO PowerPoint are power socket with your call it our that was convenience and along the way was put in AER junction box for protection and hey presto Bob's your uncle and hopefully running whatever so I said why twisted pair arm was cheaper but it does then coaxial cable but it doesn't have the control the highly tight arm tolerances are that you can get with coaxial but the cost tends to win plus is something you can do a twisted pair that you can't do with coaxial cable and that something that is referred to as common mode noise rejection common mode noise the idea is that if I run two signals and one is the mirror image of the other signal 1111 the other wire and then what I do is I am exposed to noise that is to say the that the cables tightly twisted together and I get noise on the cable the noise is going to affect each of the conductors equally all essentially equally therefore it should be possible because by comparing the two individual wires signals I should therefore be able to cancel that noise out arm through mode are you using operational amplifier you can actually cancel out the common mode noise you be surprised how effective that actually years so it's cool is very cool so common widening, noise rejection is very very handy and it's a sort of thing that has made our twisted pair very popular and in that even industrial applications so many mod bus networks are you you will just run on non-standard twisted pair cable a lot of analog instrumentation cable is run on twisted pair straight single core cable industrial locations for analog signals is essentially not done everything is done as a twisted pair for that reason and are sometimes late overall screens individual screens and this is not industrial automation so that an updated mind made is another day knows okay so twisted pair not so bad as we thought range is limited certainly with them so as kayaks and frankly it's a heck of a lot cheaper and that gave it the edge in the end so and also one you I haven't about 120 okay now this next next next next next okay I know talk about ethernet switches and point-to-point links but I think it's it's time for us to step up a level and get a little bit higher than the datalink layer and start talking about addressing the okay MAC addresses versus IP addresses so so your budget devices right but you know how you get a message from one of the other modest enough to connect them together whether on a bus when I go to a switch go either way as Mattis do you know how to get the data to work needs to be is no is no question you need to have an address of some kind no different to houses in a streetcar to say go to Bob's Road well what number on Bob's wrote what could be the number one up to 1 million Meijer to very long road but still you know Barb South Bob Houseman totally know which one that is so anyhow okay so what heck is a MAC address maybe had MAC addresses may be having I'm sure most people have are an MAC address has nothing to do with McDonald's so violently that at the waist as the media access control so named actually because the sigh are layer because the flow while not a layer but a media access layer is a group of the bottom three layers of memory serves the voluntary and media access control is a physical segment address and the uniquely defines that connected device so practically every piece of computer hardware prior to a decade ago used burned in otherwise referred to as hardcoded MAC addresses however some hardware now has the capability to refresh and modify MAC address usually through a firmware update sometimes it stored in flash memory are and so on some of the hardware that I deal with has them configurable through deep switches and jumpers not the whole MAC address mind you just a portion of it and some do the same for IP addresses thankfully it's not many anyhow automation is sometimes annoying to MAC addresses come in three types MAC 48 EU Y 48 and EY 64 EY actually stands for the extended unique identifier and as IEEE lingered at the Institute of a lot electronic and electrical engineers whatever them I think I think that's what it stands for class gosh something and didn't look up there you go anyway so the 1st to MAC are 40 and EY 48 are they used in the ethernet Wi-Fi Bluetooth for example the first two types these in ethernet Wi-Fi and Bluetooth arm just for example whereas the R 64 version is used for IPV six which is utilising FireWire in Digby in the example are more on that later I guess is all about octets down octet is are is that a set of eight yes because octet octet eight Octopus eight yet it's gonna give away what what annoys me is that octet is actually just another way of saying eight bits and can't look at those its leathery computerised that's what it means it's like it's another word for a bite which is seen octet because bite might be confusing on whatever's okay how many octets do you see 6 x 8 is 48 8 x 80 64 this is not rocket science it's in the names people so you got MAC 48 EY 48 all that's got six octets and EY 64 as a octets again like you said not rocket science it's in the name pretty damn straightforward so the first three octets their assigned to a manufacturer by governing body are in this case is the IEEE's registration authority and they administer the assignment of the identifies and these are referred to as the OU Ivy organisationally unique identifier more acronyms there were enough sodas leave the show notes to the IEEE registration for a committee we can apply for your own best alike enjoy yourself in the manner indicated MAC EY 48 so are the last three octets and the case of your 60 for the last five octets there defined by the manufacturer some manufacturers have a method some don't that bottom line is that they should all be unique so let's do some numbers shall we in theory and this is in theory this not just maximum number of permutations there are four EY 48 address combinations there are 281 trillion potential combinations that you think that's impressive have at this the EY 64 address combinations in theory there are 18 1/2 million trillion possible combinations is a lot however those numbers are in fact BS and the reason ABS is because the reality is that a single manufacturer was only operating under a single or a subset of us restricted number of the first three octets for either system so ultimately therefore if you think about anyone's manner my manufacturer who is assigned a single EY then you only have 16 1/2 million possible combinations for any EY 48 address or for 64 address you have 1 trillion or thereabouts combinations for a singles that I yet saw man a 1 trillion case when Apple shifted 1 trillion MAC it screwed arm causes not as get more UIs anyhow if they'd we have more than one EY already so you and I guess that's the point is that larger companies that manufacture network interface cards and chips and comes like Apple in Delaware is that they can have multiple oh UIs so you know it's is not to be a problem but back in the early arm to thousands myself personally actually had a MAC address conflict I was in control system hardware are but the reason was that it was actually factory firmware flash and they had mistakenly flashed it with the identical MAC addresses for reasons that I have absolutely no idea what they were smoking drinking or sniffing bad the time I don't know but anyway and Ed took me a few hours to find because not something you think to look for it's like no MAC address and an economic problem usually take appropriate you exactly my IP address is different no problems of the why Mike with the deed that them getting lost pack of the house go anonymized to study and get it stilted gone crazy anyway I was easily fixed mice are easily fixed was an easy easy but at least we did fix it which was now display a firm update I go okay IP addresses not MAC addresses IP address as they come in two flavours IPV's are IPV for IPV six and they represented decimal me as opposed to hexadecimal so you'll see IP addresses referred to in nearby numerically 0255 whereas MAC addresses I did mention as before but verily rep that will always city representing hexadecimal 00 FF for each of the octets love in the octets anyway so before four octets V6 six octets arm honestly I've covered this previously are a little bit in episode 16 where Fran showed David Legare's road and very nice piece are looking into the IP numbering qualities I refer you to both of those and were going to move on before are we going to ethernet switches though just a quick note that there are special IP addresses are to be put aside for things like broadcast messages are and are usually ER is reserved for gateways Routers usually are and everyone's favourite the loopback IP address is drum roll please Vic and are actually on the Fidelio around give you the drum roll but I can't make that noise that you just tell me what the loopback IP address is I have no idea seriously you tell me localhost on a slap Mike okays one that coeliac IP address I thought you knew that you develop your AA would refer to letters localhost I had a lot of networking stuff okay fine use and ITI knowing a gale SAS is okay find monkey Coie I have another hollow network okay fine I guess I just plug in olio and in and get it working and then forget about who is it someone said to me most is that you IP address to 127.0 and 0.1 you'll be fined then you can to the network fine just like you think arm and downgrade its you think garment idiot then answer that anyhow that's I said the time is still not funny but anyway they go so yes see a loopback IP address of the results of the use of the toys off moving on and fact actually you know before we do move on very important we took our second sponsor and that's safety and pair now savvy and pair have decided after years and years of being annoyed with existing to-do apps when shopping my God grocery shopping of shopping for anything actually they would decide to create an iOS app for the iPhone and it's called shopping as it is hard to do list apps out there and I've used a lot of them over the years but going shopping is a very specific use case for a list and if you shopping for more than just yourself then shopping really begins to shine in the best way to describe shopping as a fully collaborative shopping list at an simple and easy-to-use I picked up a figure how to use it immediately it's not cluttered with options doesn't presume that you live in a specific country or present you with hundred options are for bottle of milk is type in what you will remember buying less enter an amount if you want to that's optional and is there any list and remembers what you've entered for future reference even in the order that you buy them as you walk through the supermarket so that's cool enough but then when you share your list by email I message someone to your spouse your partner your kids and overloads that chocolate I spend less than you can add Mark off reorder items in the list as they need to anyway arthritis in real time between two iPhones the sink In less than three seconds and that was over 3G but I also love the pocket lock feature out your security conscious like I am and you've got a pass case that is nothing more annoying than having to lock your phone slip in your pocket then get back out again at the end of the aisle that you're walking down in the shopping centre just to unlock it again to look at the list were pocket lock disables the screen when it detects it in your pocket and it re-enables the screen as soon as it's removed no passcodes necessary no fuss it works really well out my wife I've used it several times and where we we used to know things and reminders of to-do apps or even on paper and I now when others go shopping with you shopping open shopping indicate you're about to start shopping and then the geolocation detects the store that your shopping at and on our shared list the other person go notification that there are that you're about to start shopping and then if they remember that unit they need to grab something for them they can tap the notification go straight to that shared list and they can quickly add that item will then appear on my list one in the shop and I can grab it while in their spray those last-minute is there anything else you need phone calls yesterday need any more okay so shopping is free to try the first month with no at after that it becomes an supported there is no no rest no loss of functionality but if you want to help out the developers you can and you can in our purchase three or 12 month and removal for a dollar 99 or $4.99 US respectively the update to fully support iOS 8-6 and 6+ is been live in the store now for a little while and it features a handy reachability feature where you pull down to add new items is been a fresh coat of paint and now you can move checked items to the bottomless decline in the longer list if you want to so please visit this URL to learn more it's safety and that S AP I ENT – pair is and follow links the App Store from there to help out the show you search for the open store but if you use that URL in your browser of choice it will help out the show thank you once again to save your pairs shopping at the not only making the shopping life a little bit easier but also for continuing to sponsor pragmatic okay ready for some switch and I am I say let's switch it up has to go to is good after the terrible okay at the net system which is so having really interested in this product you have ever net okay so ethernet switches essentially come in two flavours a layer to which the data link layer switch or a layer 3 was a network layer switch was all a bit more about layer 2 switches specifically later but before we do let's talk about what a hub is and isn't a hub not a switch now the funny thing is that when I first built an ethernet network we couldn't afford a switch we only for a hub because hubs were so much cheaper than a switch so what hub does is when a PC Aris it's a PC my septicaemia macro PC not being arm you brand biased or anything on this it's a personal computer okay so get over connotation that that the connection your brain and PC equals Windows doesn't so PC on one port sends a packet the hub then repeats that packet to every other port that is connected to it gate is pretty darn it is a hub for the catering together so essentially it creates armed the star LAN idea is essentially it creates a point-to-point link and it aggregates all the point-to-point links for all the devices connected to and turns into a shared bus in a manner of speaking so act like a repeater arm which you know it is good that is bad is whatever I know bad I guess because the problem is that if you got a relatively large network with a lot of hubs it'll saturate very quickly with traffic and the bigger it gets the worst that gets because a lot of repeating going on your okay so there are very subtly different effects when you compare and ethernet are now 10 BaseT network using hubs versus a let's say 10 base five network using AER coaxial system on a common bus and those are very subtly different effects but really it's the same kind of problem okay now I mentioned rows before are just quickly touch on that arm rows are designed essentially to be gateways the bridge to networks together and typically then be used for ISP connectivity are connecting your business network remotely via let's say a virtual private network for example into the business they are homework and into your business are the comely work for whatever then you would do that done you throughout the router essentially butts hubs and switches switches are very specific beast and dataset are very expensive and these are in the beginning switches are very expensive because they required more processing and is a good reason why I access in a hub, think that for quite a while after sale that used to be there for a while Isa cents a much cheaper and if you have or switches available in the inner eye in the IT sure your IT store of choice and now I think hubs are pretty much gone was the last time using a hub arm polygamist or presale add-on know that I've ever seen what really allowing Their 10 you're older than me so there I've seen some in use at some places where it worked before our Karen Turner okay so nowadays everything is a switch and switches are far more efficient why is the question I simple because implants are an ethernet switch learns and figures out which port to send the packet onto so unlike hub just repeated everywhere a switch will selectively send the data the traffic over the port that is gonna be where the destination that is connected to the next link or to the destination directly either or so ethernet switches are a good because each link is handled independently so each port and ethernet switch is dedicated to an individual computer which means that you can no control independently so but they've got 10 100 ethernet switch that the device connect on one port you it's stuck at 100 yellow once in the next device thanks and exports are stuck at 1010 100 110 whatever in alternation you can negotiate each of those independently without any interference to each other it can also handle some of the good switches can handle autocross over as well we took our crossover cables was any crossover cables well because one pair is to transmit one pair is for receive so what you'll do is your connected into one computer one device to another device they're both expected to be our end devices connected to a switch or a hub therefore you you expect to transmit and the receipts to be on the same are pens like computer computer you not because PC makers aided me to cease and so you would plug in a standard straight through cable between two devices and I wouldn't they would now talk to John Eaton in fact that's still probably the case but they expect to be plugged into a neatness switch study that switch would be the other way round so the problem was of course is that everyone would then buy AER some though computer nerds that wanted to go point-to-point between two computers of our switch and form a private network usually for rafter gaming like playing net do not equate net whatever you like ice do sometimes occasionally maybe an automation as well when you've only got one computer talking to another computer for the purpose of data transfer in and sizeable using our LapLink software for example all that sort of good stuff you need a crossover go crossover cable so reports on the macro smart enough to figure it out in our yes I think so most modern switches are these days they can handle autocross as now automatically detect which is got transmitting images which is receiving which is cool and handy seniors any ensuite arm cable you like so anyway arm switch is a good light now arm speed negotiation so let's say you've got a gigabit switch assuming now we've got in I case everything comes down to you gotta have all the pieces in the connection that works over to have a gigabit connection obviously need cables at all four pairs of personable stackable helps with IV not absolutely necessarily requirement especially fits over a short distance but you really probably ought to our because otherwise forget if the link is too long between them and you plug in SI Five VK we not guarantee there won't be a tighter control of the impedance and the transmission line for you to actually achieve a lot of noise to achieve gigabit so anyway bottom line is a good quality all relatively short low quality are cable and you be right for gigabit probably over short distances but still go IV can't go wrong then are not a much more these days and most cables most patsies now go are essentially Five years relatively standardless to get the cheap GGG Ultra cheap ones I gave the IDB only chant plaza got AER a gigabit rated patch lead then both ends can negotiate and say yet my switches on gigabit my devices yes I'm gigabit and they happily shake hands and say let's go gigabit baby in your often rapid however sometimes the wheels fall off there's too much noise you've got a bad connection of one on 4C device are connecting to is only 100 Mb device in which case you're stuck with the lowest value well the next hangar the highest value that is capable of each end or the interconnecting medium that brings you then stuck to 100 mag or maybe it's real bad and is stuck at 10 or worse than that you're stuck with nothing so speed negotiation for the very first things that happens once you've got that basic speed negotiation established and order crossover has been dealt with that's when the MAC address is identified say say that the device says this is my MAC address and the server then makes a note and says right this port port 10 of on on the me me being switch me are port 10 is connected to this device this MAC address and add that to its internal arm table so there would be self-doubt port in the naming mechanism will vary by manufacturer but essentially it maintains its own table arm with the port table shows a list of what device connected to what ports so some switches are also employ cynical MAC address locking and I took that as previously in episode 27 is a link that show notes and our MAC address locking it MAC address locking locking is that effect whereby you can only plug that specific device with that specific MAC address to that port otherwise alarm bells go off the communication will get locked down no data will go back and forth you'll get the order negotiate will agree a speeding or say what paying out nappy on my friend go away and in my case that's when all the security personnel came down my desk and said what Howdy thinking doing my Savi and Andy Geronimo about that list in episode 27 and again that again so once all that has happened all the levels of negotiation your crossover the MAC address of an handover if this MAC address locking the MAC address lines up it's at that point when IP addresses start to go back and forth how okay now when you want to send a packet of data and was about IP address allocations and when he wants a packet data some on your local network the art which is the address resolution protocol is used it actually based on MAC addresses first not IP addresses are because these are the switches is the answer to that is a layer 2 switches right of the network level would be layer 3 that would deal with IP routing not laid too late to his MAC it's the actual closes the physical layer whilst most of above front datalink layer so now there's a great article I blinked in the show notes on how IRP works in nauseating detail if you really want to know and I encourage you to check it out if you are that interested I however am not 10,000 foot view maybe 1000 foot or even hundred foot view but certainly not that little detail so packet has destination IP address device be sent from device a to the ethernet switch say that again a packet with a destination IP address that is the IP address of this device be sent from device a and it goes to the ethernet switch the device are yes connected to the Internet switch then checks to see if the destination IP address is in its table it notes that it is and directs the packet that devices MAC address specifically by that port if it's not in its table that sends a broadcast message to all ports asking to know if anyone knows what the MAC address is of the IP address associate with IP address if there are no responses tries gateways and Routers and so on hopefully someone comes back and says hates me and if they do it's forward on accordingly however if no one comes back than the packet fails to send the simplest example of how you can see this in action is it is a ping request or they can go to the terminal the DOS prompt and type in ping your IP address of choice and see what happens if you get a response than the switches and Routers found a path and give your response if not you get Babar failed the world is ending my God it's the end of everything else and on exactly follows dramatic but still okay at a lower folky connectivity and Renovo considered the end of everything else you do and that's that's totally and absolutely fair to the first were problem so it sounds like jumping around a little bit but I'm trying not to buy a lot of this stuff builds on prior knowledge so the problem is knowing when to break in and say what we are start here so now that's the basics of arm the basics of ethernet switches the basics of how information is routed within the local network I saw stop at the router a little bit so let's talk now about behind a router and let's talk about essentially well SOS subnets now gone into the 200 level glasses I don't know maybe maybe not let's see how we go showing subnets are critical to understanding how it is possible in the networking function on an enormous scale of the Internet so I mean imagine a world just for a second where every single ethernet switch spoke to every other ethernet switch every time a packet when out just imagine it as it wouldn't work you collapse right how we reduce that traffic load to in every other ethernet switch in existence is we create subnets little miniature networks attached to the side of the Internet if you like you know this is like a ZIP Code versus your actual street address rate yet kinda like that and the access portal to the Internet has a single IP address but the router that connects you to that single IP address then acts as the gateway and it forwards on those packets but it remembers who those packets came from so they can pass them back when the packets return but most subnets are will fix the first three octets my piece before and that gives you a total of 254 possible devices I say most I mean there's actually a bit more to it so will get that separate and is fine for most households but businesses usually will require more fix either first one or two octets and that's why a lot of home that was it will networks are going to use 192.168 point X point acts and usually will be just .0 .8 .1 point externality that how did that come to be is the question on everybody's lips while maybe this maybe isn't was a question Milos for that is because a bit weird that's okay the IETF the Internet engineering task force sounds a bit like Justice leader something I know maybe doesn't accident them only wrote Patsy had originally comments before some reason that is IT SMI some cover task force I could do some the Justice league think about AI they published I received 1918 which was not published in 1918 especially published in February 1996 requesting allocations of specific IP address ranges are private Internet and the reason that they reserve these was that these IP addresses would never be allocated in the public space to that only for private Internet or intranet actually is a more accurate description so this would mean that the following groups would be put aside forever allocated for that purpose and that purpose alone the first one of the biggest was for large corporations and need a lot of IP addresses mass 10 point X point X point X save you lockdown the first octets 10 and all the rest of referrals next 172.and the next nice numbers range from 16 to 31.X.X was a.X and X means any number from 0 to 255 and then finally the one I've already mentioned which is the one that most people are seen and that's 191 168 point X point X of which most home networks are either in a one 9168.0 point whatever okay so that way it would mean that you within your home network to have a computer call 191 168.0 .2 and I can have Mike device could be one 91 x 68.0 .2% is crazy how is that possible right it sounds crazy but it actually does work because of the rousing site letter tailgating that addresses I was resolved locally yes exactly so let's take the example of two computers a and B they each have the same address the mind as mentioned but they're connected via their respective Routers via the same gateway IP address in a local network so 191 68.0.1 let's say are but they go they are connected to the Internet you on your cyber world on my side of the world router a has a public IP address a router be hazardous public IP address be in they are different because there are different parts the world now I say they're both talking to a server and that server has IP address see just because I'm gonna keep using those now that okay so PCA and PCB have the same local IP address but they ask service see which has the site which has a its own public facing IP address for a different webpage but on the same websites are from the same server that server knows that each packet came from a request by a router at a different IP address either IP address a IP address be that's all it cares about and it sends its response to that respective router that each respective router then knows which PCI's network actually originated out request and forwards the response onto that respective PC and therefore you have ended up with what is referred to in the lingo apparently are as one to many Nat network address translation I just thought always referred that is network address translation or natural and 80 but it's correct full name is one to many Nat and that is the method by which subnets allow you to have multiple identical IP addresses all around the world on intranets and yet you can still connect each of those three gateways/Routers in the router is the gateway that's why it's kinda confusing some people say what is a router is a gateway well it's essentially to gateway router… Name it performs the function and how the point is that our that's house possible and works it sounds crazy but we think through actually does work okay so far so cool all right now that we understand the basics of rounding a network address translation house possible packets to do that now let's talk quickly about firewalls and little reports and not the mother, put your drink file or less obviously this is an alcoholic podcast although it will be a very different forecast for drink alcohol for hand and all episodes of pragmatic have been recorded sober just say no so disappoint a lot of it is disappointing and what is a firewall firewall is an access control mechanism or device and it prevents access to one or more devices on on one network from other devices on either that network or an interconnected network is that it is an access control device right it's kinda like the stop go person on the right side saying yes sure LMS is true or no get lost you can't go you shall not pass you know that's it and enforce the bottom of the mountain with a big fire breathing thing in guy got a ring and they thrown in Mount doom and blubber I react to does firewall hardware and software so Routers essentially through the network address translation create a essentially a hardware firewall I say hardware visiting really is a hardware firewall technically is handled by firmware if you prefer were running on hardware which is now not hardware its frustrating anyhow that Mynatt don't equip about that definition where that demarcation line lies let's just call a hardware firewall and move on any request and then that is originating from the intranet gets rejected and less of course you enable specific port forwarding to forward all requests to a specific port to a specific IP address on the other side of the firewall that particular methodology opening up a port sometimes people call it port forwarding can send all traffic on that sent to the public facing IP address and a gateway through to a single IP address a single computer device and I refer to that as a demilitarised zone DMC DMZ and on where Hayward pouted country come from and DMC's have their place but honestly I don't think it's really considered to be the best method to handle things sometimes it is the only way to handle things but generally speaking you know most people at home will never use DMC will never set one up so that reason I'm not gonna go any further with it because it doesn't apply to most users port forwarding can still be useful for other reasons though even for not using at a DMC like for example let's say a while back are we talked about is our dynamic DNS your dynamic IP address or may be lucky enough to have a static IP address lucky reach whatever okay maybe you go way of connecting to the public IP address at your home are Wi-Fi modem router whatever might be connecting to a computer sitting behind a network hiding their happily protected relatively from the Internet's and all the dangers lurking so you want to connect the in situ that well if you disconnect up most motives are the work you need to actually forward on the correct ports of EMC traffic in order for define a computer when you do so you had to do with that specific computers otherwise how rosters are the router know whether rapid the traffic to and unless the Travis originates from inside the network how would know you get your you can't do safe here said the computer that one is idea which one that one in another name seriously seriously which one that are the one in one no seriously no so anyway in love about that software firewalls now they screen traffic potentially at a lot of different layers of the application stack operating system level application level various levels in between toll whatever blessing the example of OS 10 why because well I just can anyway there's something called the IPF W and that actually came with OS 10 as part of FreeBSD and are also IPF the recess for Internet protocol firewall and doubt that there is a second firewall in OS X that they refer to as the application file now both of these can block TCP/IP lay requests arm from specific ports or addresses et cetera whatever you like in a loss of the things some more configurable in others it is beyond the scope of this discussion but let's just say that at an individual device level you can also have a firewall Windows has a firewall as well introduced in Windows XP if I remember correctly maybe Windows 2000 may have had anyway so that's just briefly about firewalls access control devices to screen traffic from coming into your device so that let's say you're on our side and you go and you trying to our access someone else's computer from behind a firewall or you will get is no there is no there is not usually static you'll get no response or you'll get your destination host is unreachable or selling like that you made you get a ha ha thanks for trying get bent I know whatever okay good lovely port port sportspeople at ports and while Kissimmee while one not AI IP addresses on a machine may well identify and as you need to bite device the IP layer but it's actually kinda handy to further subdivide the messaging into a virtual series of virtual constructs that is referred to as ports now I don't really see the difference not really between points in your port and calling something you connection.and adding an extra octet the end of an IP I don't really see the difference in a case on octet actually but it's more than that it's been an octet but the point easily from milk or correctly the word size a 16-bit number but the point is that ports are you essentially a virtual constructed it's a supposedly analogous to physical ports on ethernet switch or on a computer like serial ports and so on like data from this thing comes report one this comes report to & so forth but really they're completely virtual they're not real but built about ports they are still important soap think of it like an IP address is the street and the port is the house number thing that way if it helps Amini may not help but if it does help they gave me that way so some common ports that you will have heard of port 80 port 8088 is 8080 are an ass for rum wet HTTP requests are the common ones like garden FTP is a poor 20 1R HTTPS are which is secure HTTP will talk about later that staff for three our SMTP is poor 25 and there's lots and lots more and is actually Commissioner to be really care what those ports are like the ones of EMC if you really care look it up you know but essentially yet those are ports site about port forwarding I'm talking about all FTP request that they would forward port 21 to this IP address and it would then put forward all Internet are all requests from the Internet to your public facing IP address to whatever private IP address on the other side firewall for that port and ought only Horsfall id puts the DMC and watch it burn whatever okay half yard about halfway through Toure our mind we going to short show gonna keep truck in DHCP versus fixed IP gonna mention it because well you just gotta mention it so fixed IP and the bad old days man IP addresses are sent by jumpers you know and if you're an Aussie or I think actually the British also use the word jumper sweater is not a style sweater is not a cardigan no I mean jumpers as in your little physical jumper's arm marker or shorting bar if you like art or if your more modern is nothing worse than changing a jumper inside a computer and then dropping the jumper is like man wedded go demagogue got jammed up in a fan cooling fan what's mathematical noise gun beginning pink I speak from experience and I dip switch is a better but they still sucked let's face it ever unknown likes jumpers known like dip switches they suck as I said previously some controls now I still deal with every day still uses jumpers and dip switches and sucks and I thankfully in 1993 are the dynamic host configuration protocol DHCP are came about whereby IP address is to be allocated dynamically when required and then reallocated to other devices when they were no longer in use so DHCP or the DHCP server technically is usually controlled these days by the router I don't have to be but yet so technically you could actually have a a modem separate modem a separate router and you have a separate server and you could AI have the modems do that do the connection to the Internet are and you handle your fixed IP and you have a Wi-Fi router handling all the rousing and you have the server handling the DHCP if you wanted I suppose but far more common use case is you get this crummy box from your damn telco walking out however it is your ISP and I say here plug this anyone have any problems at all thumbs up and your plug it in and it'll still be DHCP for you and your wife IN EA ADSL lawyer BIOS of whatever you got annual just still be a headache anyway so on the device side it's settings like our dip obtain your IP address automatically in Windows LAN are slightly different in OS X it just means using DHCP to the benefit of using DHCP is you never accidentally defined the same IP address twice on the same network which would be bad because then you would get dip the packets packet collisions lost data and you would be very sad and we try to avoid sadness any our DHCP load can give you more than just the IP address you can also give a whole bunch of other network information which we will talk about a little bit further on in one more about how the ins and outs specifically how DHCP works then there are some links in the show notes for further reading if you really are interested okay DME were moving our way up the stack but before we work our way too much further stack let's talk a little bit about arts not too much little bit about ISP into ISP communications Up until now with intimate local intranets we can't briefly touched on our the fact that packets go out to a server on the Internet and ISP is connected to the Internet or the hell is the Internet exactly the Internet is really just a bunch of switches connected together this really not much else to it from a theoretical point of view practically speaking no ISP's talk have to shuffle the data around somehow and how they do that and they do that by backbone somewhat referred to as backbones are traditionally backbones were all are circuit switched data now talk about circuit switched data previously and the idea is packets which were circuit switched is that you find talking on phone I pick up the phone and land I get time slot in a digital backbone and that timeslot will be yellow I get this channel on this T1 and is assigned my phone call significant significant bits per second and is reserved for me and that circuit is switched all the way through the network the matter which telephone exchange I go through I get allocated slot once I was not our counter all of my connections to the destination the destination will ring ring ring your Vic. Number nuns up there go thanks by and I hang up and then those circuits are then have put back into the pool and someone else can use them but during the duration of that call that circuit is ours right one up one down fixed rate always ours whether we talk whether we don't horrendously inefficient because anything about a lot of this time you speak is not talking it's pausing anomie let's face it that's why arm Marco arm and some smart speed works so well because on pod casts an overcast note and a sponsor yes it is a good at and I what I mean smart speed is is awesome you get addicted to smart speed benefits and understand and then you listen to them talk live like she's the talk and slow anyway and one that thanks Marco for that unintended side-effect of your run anyway arm so not to our forecasting apps but that the point and try to make is that are there are the bearers that the are the backbones all used to be circuit switched and eventually they were better methods determined so are some of the connected technology the carrier itself like the fibre optics is the fibrotic line drivers and receivers that I came across what they will do as they would take all the data in different formats be circuit switched data packets which data and they would are essentially combined them into essentially a wavelength division multiplexing fibrotic our transceiver that's a big mouth for the male product I came across was working at Nortel wasn't part of the Wiles division but our equipment connected into it are was something close to 192 this link shows if you're interested he was cutting edge of the time was a 10 Gb STM SWD and fibre-optic our interface art than I could handle 16 different wavelengths per fibre core that was in a cutting-edge time our use of the estate get you into wavelength interferences develop problems up that there was no 97 cutting-edge stuff that supported some our site are SDH which is stars and a sorry sonnet is a synchronous optical network and a CHS interested on digital hierarchy and that formed our society is the basis for round of applause which is our packet of sonnet G is a haven I do that you know it's like if there is that there is an acronym inside an acronym size like poles as opposed to pose sonnet which I just pose sonnet pose sonnet or pass on it doesn't really work so I guess it's poles but puzzles extensive point-of-sale so anyway whatever blames this scope Cisco had played a big role in development and pushing that the marketer for run deposit most Internet traffic carrier backbones uses poles and one form or another and is much more complicated than that technically but essentially imagine your traffic your packets that you're sending in trying to receive and a million other packets being round over subsea cable between the continents extracted and standard switched out at the other end by a bunch of ethernet switches and Routers the routs can be learned by the broadcast methodology can be manually configured for load sharing or balancing so you could say I want all IP addresses from this service main hub this main hub to go via this link for this other link or you can just let them learn either way link goes down I want a redundant link anyway all this load sharing load balancing clustering how ISPs balance them their traffic loads and all that is actually really fascinating but for the average individual suffice to say yes it's done yes it exists known octagon in more detail about it because I don't think it's interesting enough well I did it interesting but not itching enough so for the third of this discussion so there is a really interesting article that I think the show is called Internet cost structures and interconnection agreements as it is a really fascinating historical progression of how ISPs have evolved with connection agreements from the circus which days arm through ATM frame relay and all of the pack over sonnet and all the different arm technologies have developed and evolved into how they evolve their connection agreements that their line leasing contracts and how all that is passed on to us the end consumers of our of their services such that we best pay you a fixed rate and of course some people see the raw figures and say but that's ridiculous their weapon is often a psyche of the last mile is quite expensive to maintain plus you deal with people and that's always expensive because people complain all the time like me anyway how separates it happens a lot indeed right D and S bins bins is our friend because we human beings don't like numbers because our brains don't like numbers must incur mathematical genius but I got an eidetic memory which is minor okay so IP addresses are all well and lovely and a beautiful sight to behold acting under not like how the heck is it possible for me to remember them because the human brain doesn't remember numbers we just don't we sit there and we recite phone numbers I can recite my phone number from when I was a child because I had to learn it when I was at school in fact I connection remember most my phone numbers most the place a little round the world because I just got a weird memory for numbers but I accept the fact that I'm weird and most people don't and Frank I can't remember IP addresses apartment risen by 0.0.1 because you face I got scammed once and now and forever angry but the point is that they had to come up with some way of dealing with this problem we say visit may reset don't visit google but either way we say visit we don't say visit one we don't and there's lots sevens and that she rate there demonstrated is masticated IP address ever I am totally registering that so how to get around this the answer was DNS the domain name system sometimes referred to as domain name servers DNS same abbreviation subtly different meaning solves this problem back my stay at uni DNS was not a big thing certainly a lot of sites had them a lot of institutions had them but there was still a lot of servers especially the good ones in army they were just IP addresses and watching the IP address as you wrote them down and you kept them somewhere safe because the idea and they didn't register with DNS of Virgin Mary various reasons anyhow and a lot of protocols I guess were using some of the time you like IRC are telnet even you write the addresses were okay it was early days but is hard remember so the best way easiest way things are DNS like a phonebook for IP addresses now the thing is though ARPANET actually had a file a text file called hosts.txt.txt and that and that That information but it really wasn't that useful was an extendable is easily searchable didn't handle a whole bunch of educators assignment essentially was abandoned the original DNS specification was actually written in 1983 is a pretty early on but it was greatly extended in terms of its usefulness in 1987 and in fact the most common the NSF site DNS server software in use or bind and bind is the Berkely Internet name domain as Ashley written originally 95 for UNIX but it was ported to Windows NT in 1991 antedates still the most popular used DNS server software is a niche application I'll admit so is probably not much competitive benefit other people to go and develop a competitive competing platform product but anyway so what the hell is our domain everyone knows what domain is made don't know what whites call bodies and fact one of the sponsors of pragmatic hover is a domain registrar which will talk about in a minute are they not sponsoring this episode by the way but still domain names are essentially what we would say or WW or whatever those are all examples of the main domains tech that's the domain of the eyesight so domain names are broken down into segments sometimes there are just recall parts and more often thereafter formally referred to as labels are separated by full stops so domains are red backwards matter backwards I don't mean you read them like the results of that should read the RSS sermon not I mean I mean you read them from right to left as opposed to left to right and I mean backwards only from a Western predominant Western writing point of view because it's forwards yet we think about from an Arabic or Hebrew point of view and actually if you are interested there is link in the shadows about all languages in the world are actually read out the other way around so there you go anyhow that's if you really really interested I'm sure someone is okay so the specific rightmost domain is referred to as a TLD top level domain, until these and most anyway three coats airway and country codes are also appended on the far right and although you can argue that technically these are actually the top level domain they not usually referred to as the top-level domain there are usually referred to just as the country or the country domain or sometimes they're combined with the what's referred to as the TLD and is combined is called a TLD so for the New Zealand being Australia of New Zealand or for example if you're in the United Kingdom so you these country codes plus there TLD can somewhat be referred to as the TLD so you it's it's kind of funny but the weird thing is start out very early on as a lot of the main stuff is in your you guessed it yay got ARPANET you got Berkely where is all that stuff it's on states a lot of stuff started in America typically does not have.US on the end of fact and give .us despite the fact that .us is the United States actual country are code hardly ever used some say it's implicit but it's also it's also not genuine because tech distortion is tech it's no technically it's hot it's it' as table countries from their forwards implicitly from the US but I'm in Australia annoying as hell isn't and let's be honest as well are are what some are ATP.FM are relay.FM FM is French Micronesia neither of those actually in French Micronesia okay FM just sounds cool good sound like a FM radio frequency modulation FM yell baby to his being right you don't have to live in the country where that actual TLD country go code whatever court you live in a country arm but may not have but the registrar from it has to be I believe are have access to the owner who is in the country in order to use that domain environment correctly anyway I'm sure someone could never write about irrespective so that's the TLD's but the actual domain name the thing that we think of as the domain name is at is the next component to the left of that so for example our apples is Apple Sega so Apple is there domain googles is so you was let Google that to get a better are you seeing the pan are you getting it unsteadily devices are you getting it these are not great… Fantastic I get nowt beyond this sometimes you'll see domain broken down even further and is generally either by subdomain tourists I guess what I like to call a service type or service class so subdomains can be forced subject specific or service specific purposes so are anything you want really is no rules but for a while going back a year and 1/2 ago so before pregnancy yet I was before pragmatic arm when Indy are I had pod support cast was actually a subdomain underneath our tech distortion and I had a separate completely separate WordPress installation completely separate WordPress arm everything because I was managing a podcast portion the website that used to host existential that was done under its own WordPress installations and website and was hosted under a subdirectory on the same server so the same server was actually hosting two different websites arm you know not not a big deal technically it is that's why I chose the time eventually I had a divergence I do work on our like the theme files on one side of like I'd really like this available on our site and had a port from one of the other and the Campana neck with code bases and my girl so grumble grumble on to develop a grumble grumble I've had enough spit the dummy moves down Megan and I combined the two when I got rid of my subdomain when you buy domain you can usually then register as many subdomains you want usually to you so arm I also mention however a service type so for example let's say you got a service like an FTP server or a Web server well if you are an FTP server you might say or it is a Web server you might say WW W World Wide but in most cases these days it's all about the weapon domains are about the web therefore you say tech you have the W WW in front because there is no other service associated with tech did just that it isn't okay make sense that okay so bumper-to-bumper finally now we are at URLs uniform reference locator which is essentially the name of the website it's domain and the purpose of that domain is to make it memorable so I say to you visit tech and then you like is that one word is that too was zero – the Millers and_is it uppercase lowercase D the d is it is a tech as in the RTC or TC H or does he mean technology or you as I can say every now and then I do regret my choice of tech distortion but oh well most people get it right but the problem is of course all the common words are long gone they were long gone a long time ago and they get a lot of money so people will have this thing will sit on a domain name and I say I'm sitting on why because armoured pain in the asked I'm never gonna ever brew a cup of coffee but someone else's and then I want and they can pay me $200 million for it so good luck with that indeed so year every now and then these guys get lucky and someone a big corporation really really wants it and set up a stupid amount of money for it because it matters I remember Apple pay a lot of money I think it was for and is either paid a fair bit for our I think Marco may have paid a reasonable mouth overcast FM I can't remember and I padlocked the trademark but the people pay money for these things because it's all about the brand anyhow so tech the goat that is a URL technically you got at HTTP:// that to be a complete URL but that's another story for later in the podcast will get to it okay all of this whole of that BS just so I don't have to remember one so deaconesses domain name service does more than just hold that information it does a whole lot more is set is extended in 97 so they are a whole bunch of really cool stuff they store more than just the IP address but are not about everything that they store can store there is a link the shards of your note every single thing that they store but here's the thing or two about a key ones but rather will but still but the ones I use so first of all a or four A0 AAAA if you like AAAA Soay or AAAA a arm IPV four and IPV six respectively and that is that a domain association essentially is the most important one it was the reason for being initially lease the DNS and it returns the IP address say type in the domain and you associate you're a record is associated with the IP address of your server which is hopefully a fixed IP trouble that is not so that was the one you lot see name stands for canonical name record all it is is an alias of one name to another CSA arm Bob and the alias of Bob's Bobby Mick Bob on whatever MX mail exchange record he will have these in short they've ever done email stuff mail servers and some mail exchange record maps a domain to a main mail transfer agent for that domain but the only man MX records you can set a priority and this allows you to have our route backups are much bigger mail service so that you can do as you have like 234 of these so that if one mail server dies you have a backup mail so because mail servers can be low balance load shared redundancy on rubbish so you not want talking to not not be talking much about email this episode frankly because it bores me to tears that's okay anyhow suffice to say MX records that's what they do GXT T XT as opposed TNT's tax record now doesn't actually do anything but store textual information well, that's probing all that surprising actually can think of it more recently it's been use the method of determining ownership of a domain soap for example when I changed from a dodgy domain registrar to an awesome one being hover our I moved across my office 365 exchange entries are for example so I see I struggled through 65 NIEs exchange service in my tech email is actually hosted office 365 no Microsoft are not sponsor any arm your answer at T XT entry to prove to Microsoft that you actually own the domain in question after the move is completed that text entry serves no real purpose or I do is to stop other people stealing and redirecting your mail that's all in the in the text entry provides a mechanism to prove yes you have right privileges to that DNS record so it's safe to know that you are the owner of that domain okay Larson dimensions as are the sort short full-service locator now is this a Sicilian more modern and frankly far more multipurpose entry than simple MX records office 365 example uses these are for four links are communicator are a bunch of stuff so are SRV entries are useful for that okay so these records are held by so-called root name servers to medical names of you and when when a request goes out to a DNS are root name server are the query is recursive and is recursive on the bar on the essentially in the in the order of the domain so distortion.podcast.W WW say that they are essentially are recursive through a series of tables to the point at which they resolved hopefully when IP address that relates to that domain and that data is then returned such that your computers can then say right I've looked up the phone book now in a IP address let's go give me data so because all of this can be time-consuming DNS records are usually very heavily cased because let's face it IP address is read a change very often the admins yet exactly savage running site or specify different TTL it's time to live not transistor transistor logic to push updated IP addresses and namespace records far more quickly are but honestly even with that there can still be big lags in different DNS servers around the world because their casing rates may not observe the TTL for a bunch of different reasons traditionally you get quite a 24 to 48 hours maximum however the reality in my experience last 12 months might be changing servers of done a fair few times last few mining done three times the last last 12 months arm with the podcast instead American changing to cloud shards for example distillation all that it really only took an hour to and is fully propagated and is tool are available on the web called the global DNS propagation checker Basilica show notes and I've used it regularly there are others it's young it's true I use it so you might find useful is not necessarily recommendation but it works okay is free after what I do anyway is free and you can check to see how you DNS records are propagating around the world with key root name servers in their list has a pretty map the world in a big red X or a big green tech at each of those locations were root our name servers located so how do I get me one of these domains the answer is you go and speak to a registrar is a mention before just like a previous sponsor of pragmatic hover and are hover is because one of the best in the business now you pay an annual fee or even two or three or 45 year if you'd like to reserve that long and you can reserve that domain name are and then at that point you can choose where to host the DMS and you which names of students are now my personal case I use DNS are hover but for a while I actually pointed are the DNS of hobbits name servers a digital lotion and I then managed all of my DNS entries from digital lotion I have my reasons for doing at the time but now no longer digital lotion I decided to simply move all my DNS entries and let them be handled at that hover instead and it works fine so anyway AR yes exactly hover rocks so okay so did it to do right what interesting points to note though is that some people are saying the domains dying the domains of had their day and as a couple reasons why people saying that there is a high density of these were released about 1218 months ago things for example I think in.officer I do know that Hubbard was.crazy stuff and how those steal these will help but the truth is that those steal these don't change the fact that search and search engines have on social media as well which is a different form of searches for more selective duration that has partly removed not completely but partly remove the need for the absolute need for a domain so a lot of people live for example on and in this episode are in every episode pragmatic at the end I tell people about the pragmatic show twitter account but their feminine link in the individual show notes for that until recently and even then it only appears on the show notes if you have the full show notes of younger iTunes doesn't appear in the iTunes show notes knowledge reasons by noting whatever doesn't really matter that much because most people can type in your pragmatic show and into Google and Satan pragmatic show twitter and you'll come up with the correct link so suddenly I don't need to say show all one word or lower case I don't say that people are to write down promoted remember it is typed into Google we type inductor go or your search engine of choice being whatever point is that do you really need DNS if you want to know about me you can just type in John CG into Google and it will tell you and bring up tech distortion may not be the first mate is the third fourth fifth sixth seventh entry don't know probably doesn't matter either way you know it's just you so any source the point was the point getting I'm getting at DNS is less domains are less critical today than they have been in the past because search is so good I had that said I still think it's absolutely critical if you have a business online any way be taken seriously you have a domain I honestly I still genuinely believe that a I hesitate to recommend to anyone that you rely on third-party service for people to find your service you if your solution is go search Google a finder's when Google goes in the tank you got nothing now and Google's gonna gonna take but if you rely on third-party services the DNS is and is it is a standard is handled by multiple registrars distributed around the world there are multiple root domain servers all at name servers all around the world it's heavily redundant highly specific highly specified and it works well well it works well enough so why would you then pander all that power over to a search engine owned by a company and that company is has proprietary search technology and could go under tomorrow because Larry Page and Sir Gabriel decide to you go on that flight to Mars and never come back I don't know this is a law better than that build their own planet and go and move their physical damage their money that are still with syllable planet player building a like slightly but fast okay so bottom line is are made with Irish and so was the planet study bar fight is this guy you know bottomline note is that DNS servers themselves are just servers okay there a device at a specific IP address so that begs the question how does your PC know where to find the phonebook it's just in the kitchen under the sink go look at that wasn't on a back and if that wasn't funny it's because it wasn't funny so how is it no well I said before if you recall not so long ago although it may seem like an eternity at this point who can say I settles initial show are using our beer having surveys pastored by DHCP so when you get allocate the IP address you can pass on the information as well potentially don't have to which you can so then how does the router let's assume it's your router that is doing a DHCP how is it no well that's simple when it connects up to the Internet service provider saying it's a Wi-Fi modem router let's say it will connect up and you'll say hello Mr ISP or Mrs ISP not wishing to be gender specific since it's actually not alive doesn't matter so I'm obsessing about and how the ISP will say we have a DNS server and it is the best in the whole world ever sucks your horse I believe you anyway and was used to use them as they now rely can never lie totally solid soul on every level anyhow so ill just take their DNS server settings will be passed to your router and then to your computer or your device whatever might be iPad smart phone android tablet doesn't matter you know you will be passed on so that's how you know the IP address of the DNS servers once you've got that information of course you can do a DNS look up it again IP address and then of course you are off at the races as they say however let's just say you don't lie do that you say I like my ISP line force to use them for reasons that I will not go into but yes I will use my own DNS server twice and my own I mean I want choose my own well Google amongst other things being that search have their own DNS servers that are rumoured to be rather quick dish regularly updated and just in a shiny and generally sexier apparently depends on which gig you talk to no kidding whatever Google DNS what else they gonna call it their primary IPV four is famously famously I know I know this only people know this 88888 the secondary is and yes our DNS servers typically come in pairs of primary and secondary such that the Prime Minister unavailable secondary which is a complete copy of the primary is there in case of outage failure whatever now the IPV six addresses are way too long so who cares if you really care go look up Ms Linda show notes if you're interested okay so that's DNS okay we are building up our layers Vic you still with us I am fine good you ever lost rear good has to start now but I have a I do now have a how listeners are going out there is that the same kind of place are the three XLS by now you have prepared either three axing they stopped all the gifts given up all that all that is love in all the same wins again to get to go far never talk about golfer or Archie not talking about Archie okay HTTP hello there are two people no solid stands for hypertext transfer protocol is stencil that is the primary Internet protocol that I am going to discuss I am not going to talk about any of the others of the application lie because let's face it pretty much everyone is in use HTTP at some point where they realise it or not and only a handful use IRC FTP whatever some only go talk about HTTP if that is a problem I don't care they go fully first fully document standard version 1.0 appeared in 1996 with 1.1's official release is a draft release not long after that that the official one was released in 1999 as it stands today technically HTTP 1.1 is what we are still using however that company we keep on going on about Google them they cannot with this they designed this thing called BD and is not spare anything of speedy without any valves on it and you pretty much got S Pty speedy of Dallas speedy I wonder how could be speedy of our vows but anyhow okay so I think and Yates let some people say it's it was totally developed as a response to speedy and psych well maybe speedy kind of gave them a kick in the pants I guess is that the definition of being motivated supposed but now how they feel and what kind of boot is a steel captain definitely anyway the IES G I'm sick of explaining what ISG and I rather damn thing stands for safe and looked up yourself ISG approved HTTP originally was called to point over the neighbours said in our dot points are so nine Eastwoods chemical HTTP to and they have now as of last month February 2015 it was this an official in the future lies in Exmouth in last month sorry and I want to map it is a proposed they may still be playing at that they might bar and it's a have been published as a proposed standard so it is still not technically a released standard yet it could be months it could be years but therefore I am not talking about hasty to be our one versus 1.1 versus one versus two dollar what you call it I'm not talking about otherwise we can be dead before I finish instead was in a focus on hasty P1 .1 what is and how it works in a nutshell okay in a nutshell and this is me in a nutshell help a nutshell the go Austin Powers reference moving on when you load a webpage in a browser it is called a HTTP session HTTP session is really a series of network request responses HTTP client which is a web browser and pretty much my promontory case most cases I guess is safe to say most cases will initiate the request by setting up a TCP which is Transmission control protocol connection to that previously to a particular port on the server ports we talked about those typically port 80 occasionally port 8080 now a server running a Web server application itself to listen on that port or ports and waits for a client request message so Sydney listen send somebody come out with something please please set me up for something thank you upon receiving said request from the client the server will send back a status line some might HTTP/1.1 200 okay is in that arm with a message with it hopefully is not for a four not found also in that would be bad or at least not visible on a constructive knowledge looking for unless you are looking for a four-page to some hilarious anyway the top three server applications in the world and I sit me Web server applications in the world at the moment are can you guess what they are actually are Vic Web server applications top three go well I know Apache that the what I plead with and that is certainly one of one battle to another one arm I was out of now a lot of attention to this your cold monkey there this key former canal and find okay the engine acts that someone I use our analytical use and next rocks is very very cool and cause Microsoft IIS interview not IRS stands for those Internet information services and regrettably I did not have to look that up anyway so arm just out of interest if anyone is and is interested and if you're soliciting tech distortion used to run up a run Apache are but when I brought pragmatic over arm to the site when I went indie I had moved and next are based because Apache can dying are and next handle gorilla traffic yet W and next perform is far better than Apache for surges in our spikes in traffic such that when the episode goes live there is a massive our surge of download requests and page requests so when that happens our engineers responds quickly enough on our very light amount of server power grows Apache just falls over so I tried tweaking Apache tried everything that I could think of that I read about and it just did not fix it switch on and next fix and so now had a rocksolid reputation Apache is rocksolid it just can't handle just that load that saw like some people prefer Apache problems of different reasons and what they'll do instead is they'll have far above the server load sharing they'll do you not have more powerful servers maybe inserting a cheapskate like me and running on a five dollar digital lotion server or even better a yard and $18 a year VPS at cloud shards know that is not the show but they probably should anyhow and Michael I love my cloud shards VPS running now and has not fallen over yet running engine next year so data that are way up to yes right good good good it's easy to get lost on 12 pages of notes believe me so servers are typically running a flavour all of Lennox or Windows server some flavour Windows server 2003 2008 2000 God knows what are all Lennox like you know Red Hat all go cheese to Ubuntu or not not as common Avante for running so that Gay can do anyway I write so our CMYK's RT distortions running on centre six arm with and next as its Web server and Stanek is its arm CMS content management system it is different and contains all the web the actual data are it's a Stanek is now most tech sources are heavily cased it used to have a lot of PHP crunching the background now I've got arm a layer of casing and there is not using varnish if you're curious how to play didn't think it needed because that AMEX got some pretty good casing our capabilities built into it okay quickly what talk about our HTTP and HTTPS so hey CPS is our Hypertext transfer protocol secure so you could argue that you've got secure and nonsecure HTTP so secure allows end to end encryption between the client and the server that to work it's our requires a valid trusted server certificate from a certificate governing body and we took medicine episode 55 in August anything else about so if you really care guide listen some more of the common HTTP requests at the HTTP layer include yet head post put connect and options is theirs I see more than that but those are the common ones and of those the far most common ones that I've come across are yet post so get is the common most common request the web browser will put out they'll say you get index.html are from tech and that that is that is all get sent out so okay his typical request right this is what one would would sort would look like a typical request for the root page from tech in HTTP would look like this gap/index.html HTTP/1.1 so that tells the standard is to get request this is that if specific file and looking for host would be tech that set backs to get request that would go in the packet as the packet payload my IP address to the IP address of the server that I've then determined because the tech will get resolved down to an IP address and go the IP address of the server via dear the DNS will resolve that it will go to the IP address of the server the server will then get that packet it'll it'll have a look at the message payload in will say right either get request for this and so on who handles that what's coming on port 80 so who's listening on port 80 engine exercising on port 80 great engine next says to get request a case of you this file checks a bunch of things and says right on our package of a packet message in response to it to get request so the response coming back from engine next one will look something like this HTTP/1.1 200 okay date blah blah blah some time and date usually in GMT server will then tell you what's the service of Eli engine next version blah on server operating system blah blah blah whatever last modified dates blah blah some date and who cares arm then E tag is actually short for the entity tag mass in hexadecimal is actually used are two is a form of figuring out dark case versioning and validation on the Yama client site because as a location going on are so that you can tell the version you getting is the same as the version that the server has are content type are in this particular request can be text/HTML Set of UTF-8 most likely are content length how belong in the year Mr Scobee invites except ranges invites connection close and then of course followed by the actual payload of HTML itself and I mean HTML can sometimes get HTTP and ASML mixed up the two different things HTML is Hypertext markup language not the protocol HTTPS protocol HTML is seen as a text markup language and I alluded to this minute set right and the web browser's job is then displayed HTML in a human readable way okay so I know I'm not talking about HTML that is just not so because bandwidth is so precious and I say that like it's less precious these days I guess so but it has been very precious and in remains precious for many people are one on bad quality Internet connections or in places that have unreliable electric supply and sound them with this yes Ben with his precious arm so clients will rely heavily on client side casing and now keep the local copies of regulated webpages images or any other content so that you don't have to re-downloaded every single time the pages refreshed in eight minutes is usually a good thing because it cuts down the time it takes its quicker read from the hard drive or solid state drive in your local device that is to downloading over the Internet generally speaking that is the case but it can be a pain in the neck if the server has an update or a correction applied to their website and although engine X Apaches are serving is serving up the correct latest version your client is cased an old version SO all cases have an expiry time if your cased has expired yet you won't see the update I mean there are manual ways to clear the case being a web browser you are using but you know that way you get the absolute latest version in a soap this is something to be aware of anyway okay so that in a nutshell is from web browser on your device to the server and back again how the Internet works times hundreds of millions of people and devices it sounds like he couldn't possibly scale it couldn't possibly work and honestly I'm sometimes stunned that it does but it does work and it works very well it's wonderful it is a wonderful thing so as a way to wrap this up and tie this together in this the mother of all dam pragmatic topics arm I just want to try and none play the scenario fully okay here we go I'm sitting at my desk top my laptop my smart phone or tablet connected by Wi-Fi most likely to the Internet home by a web browser I type in to do a search what happens you devices connected to the network at some point in the past obtain IP address the DNS server settings from the DHCP server which happens to be a Wi-Fi router which happens to be the annoying boxer ISP shoved in your hands and you signed up but what the hell right you web browser assembles a request to sends it to the router who having no idea what that actually means has no history in case the go to the ISPs DNS server gets a deer doesn't DNS resolve to get the IP address which by the way that's the IP address of then forwards on the request packet request packets to the eye to that IP address the first stop for the package is the ISP and that knows that the addresses in America based on its rounding history let's say that is coming from outside of America yard UK Europe Asia Australia wherever Kate Antarctica Munoz and falls it onto an ethernet switch or portal in the near nearest big city where it was allocated to go next which then passes it on to a backbone cable across the ocean comes out in America and passes through a few more switches before ending's server at that IP address I mentioned before I'm now ignoring the localised country redirecting any other local casing server side load balancing let's all just assume it's one server with one IP address otherwise will never finish the dam episode but yes okay I know it's not quite that simple but that's simple enough the google icon server opens the packet and HTTP serving software of choice Apache engine X whatever hell google using and I'm probably should know that but I don't and I don't care at this point responds with a series of packets and those packets of data will include images text maybe some PHP's and around the background server to serve up something specific to the request and the data gets sent back to the original location with the originators IP address reverse translated back to the local network again via the router that left through eventually now the web browser on your device will receive those packets and unwrap them and assemble them it'll probably get the packets via exactly the same round but not necessarily across the Internet could go completely different way just don't know probably in the right order but again not necessarily some may go some parts and make another path but hopefully then it will reorder them into the correct sequence if that's required and probably you will receive those packets quickly except if they live in my house in which case it will then display all the information the screen of your device and cause of HTTP standard and all it took was your device a Wi-Fi modem router ISPs made in the ISPs background transoceanic subsea cable ISPs telco switches in America google service which is not an infrastructure to make it work blue now have a think about all the software all the hardware all the firm well the electricity is every single standard required every single level of the TCP/IP stack not to mention the damn web browser just to make that work welcome to the Internet and when done excellent we thank Allegra is good okay we made we did we survived holy crap with the stealthy Internet that that are my God well I'd say it's time that we wrap this up now before the show ends if you still with me before the show ends in next week will be our last show I have one final final super final totally promises the final vote listeners can participate in if they want to go to tech and there will be a link in the show notes if you don't go to that domain and you can vote on your favourite episodes of the show is anonymous if you want to be be telling results for the final episode next week now as an incentive for those that are interested I'm going to pick out three random entries with valid email addresses that will be announced during the final episode and they will each get a free sticker sent out to them wherever they may be cynical school fantastic well if you would like to talk more about this you can reach me on Twitter and John CG and you can read my writing and your Cygnus podcast and other others that I've made the pastoral host eyesight tech and that is a domain yes if you'd like to get in touch with Vic was the best way to get they can phone me on Twitter advocates and lawn next year at through the Internet and if he likes any feedback please use the feedback from the website is hosted using static CMS on an engine X Web server brother and that we also function to this episode and the pod casts pragmatic you can follow pragmatics on Twitter decision announcements and other related stuff I'd also like to say final thank you to both of our sponsors for this episode firstly to it is anything you'd like to learn about and you're looking for an easy and affordable way to learn than can help you out instantly stream thousands of courses created by experts in the fields of business software web development graphic design and lots more visit LY to feed your curious mind and get a free trial there is something for everyone to learn what waiting for also like to thank Sadie and Pere in the iOS and shopping are sponsoring pragmatic once again if you're going shopping anyway great collaborative shopping list and then shopping can help you out and free for the first months I want to check out safety and SAPI ENT – Pere is make sure you check them out everybody thank you everybody for listening providing for that and making it the most popular voted for most are most interested in topic and I imagine afterwards cut the longest episode of pragmatic ever so thank you to the listeners and are making me do it right we made it there, it was still alive yes right thanks everyone and thanks again Vic that you think you Internet thank you and yeah Internet racks give a cricket problem yes I have cricket problems is nothing I can do about a man though I know that you can do about it you were being invaded or if it was a free and somewhere and unless I do the Monte Burns pushbutton and release the poison gas to kill the crickets I it's good job I know I know it's fine and as personality and character thing nearly deadďż˝
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Show Notes

Stickers Direct Links:

Previous Related Episodes:

Historical Overviews:

Token Rings:

OSI and TCP/IP Stacks:

The Physical Layer:


Intranets and Firewalls:

Backbones and ISP Backhaul Costs:


World Wide Web:

Related Links:

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Vic Hudson

Vic Hudson

Vic is the host of the App Story Podcast and is the developer behind Money Pilot for iOS.

John Chidgey

John Chidgey

John is an Electrical, Instrumentation and Control Systems Engineer, software developer, podcaster, vocal actor and runs TechDistortion and the Engineered Network. John is a Chartered Professional Engineer in both Electrical Engineering and Information, Telecommunications and Electronics Engineering (ITEE) and a semi-regular conference speaker.

John has produced and appeared on many podcasts including Pragmatic and Causality and is available for hire for Vocal Acting or advertising. He has experience and interest in HMI Design, Alarm Management, Cyber-security and Root Cause Analysis.

You can find him on the Fediverse and on Twitter.