 So let's today just talk a little bit about what do we mean by data communications and computer networks? For most of you, you may know this already. Very simple, nothing much that's new to you, just enough to get started for this course and then we'll go through the admin stuff. What is data communications? The course is called Introduction to Data Communications. What do we mean by data communications? Well, when we communicate, we're sharing information. So the idea of this lecture is I share information that I know to each of you. So we're communicating when you talk to someone, face to face talking, then we're sharing information in a local proximity that is over a local area. When we do it across some distance, maybe on a telephone, then that's considered remote sharing. So data communications, communications is when we share information. Data communications, well, what do we mean by data? Well, that's the information being shared and we're talking about computer communications. So some simple examples of the data, text, text files, ASCII characters, numbers, zeros and ones, most things converted back to binary, images, audio, video. So we want to share this information between multiple entities. The most common example is between two entities from one to another. So data communications is the exchange of data, exchange of information between two or more devices. Those devices usually are some computer device. And via some transmission medium, we'll see that to get information from one point to another, we need to send that information through some medium. And the type of medium available has an impact on how well that works. The most examples we think of is between two devices. That is when you talk to a friend, it's from one person to another. When you talk on a phone, you usually call one other person. It's point to point, one person communicating with one other. But there are many examples also where it's more than two devices communicating. I'm communicating to more than one person at the moment. So I'm transmitting information and we have 30-odd people receiving that information, hopefully understanding it as we go. Same with computer networks. We can have situations where we have one computer communicating to multiple computers at the same time. So what do we mean by data communications, exchanging data between two or more devices via some transmission medium, via some medium? When I talk to you, maybe without the microphone, what's the medium that we're using? Air would be a good description. The medium is, you think it's the thing in between the devices communicating. In this case, I'm sending some, if we ignore the microphone, I'm sending some audio or sound waves out my mouth. Those waves are traversing the air and going to your ears. So the medium is the thing in between those devices that are communicating. Of course, when it comes to computer networks, we often use some wiring, some optical fiber, but we can also use wireless, also use the air. So we want to be able to allow our computer devices to communicate with each other. Usually, sometimes across a small distance, but nowadays more so across a large distance, anywhere in the world we'll see. When we communicate, we want to provide effective communications. It works well. Some basic measures of effective data communications are delivery, accuracy and timeliness. Delivery means that when we send our data, it should go to the device that information is intended to. It should go to the right destination. You get delivered correctly. Accuracy, the information received is an accurate representation of the information that was sent. And timeliness, that the time between sending and receiving should be reasonable, short. And depending upon the application, these measures vary in terms of importance. The example that explains these in a different way, you want to send an email and you want to send it to someone you have great affection for. You've fallen in love with someone. You want to send them an email declaring that love. You write an email, you write your message, you type in the two address, you press send and you put in the correct address that of the person you want to receive this love letter. It goes through the internet, the magic of the internet and it goes and the internet delivers it to this other person who you don't really like. They receive this email saying, I love you and in this case it would be ineffective communications because the message that you wanted to get has gone to the wrong person. So a simple example is for delivery, when we set a particular destination, our network or our communication system must deliver that information to that destination and not to some other destination. So delivery is almost the obvious one. We want to be able to deliver the information to the correct destination. What about accuracy? I write my love letter. I love you, whatever, and I press send. The email goes through the internet. Something happens in the internet and the words change at the receiver. The girl receives the email and it says, I hate you. Again, ineffective communications because I haven't achieved what I want to achieve. If I have one intended message and a different message is received, then that's ineffective. So what is received should be an accurate representation of the data sent. Now, accurate representation doesn't mean it has to be identical. With an email it should be. I send an email, I love you. What's received must be the exact same for it to be accurate. But with some communications, for example, voice communications, when I talk, the exact sound waves that I generate, what the person at the other end point receives may be slightly different. As long as they can still make out my voice and make out what I'm saying, that may be accurate enough. So depending upon the application, accuracy has different measures, different levels of importance. Timeliness, okay, you can think of an example. I send a message and I send my email, I love you. And it takes one year to get to the destination. In that one year she's gone and got married to someone else. So we need to consider that we have, we need to consider these three different measures for what is effective data communications. In the next topic, and we'll start that tomorrow, we'll talk about some more specific measures that try to achieve this. If we look at a communication system now, so if we try to break this concept, we want to communicate information from one point via some transmission medium to another point, can we describe it in some model so we can analyze it and design it well? Well, this is a simple communications model that applies to many systems, not all, but most. We can break the entities or the parts into five different blocks. We have a source, some device that generates data to be transmitted. For example, with an email, my computer may be the source. In fact, the user, me, who sits at the computer, types in the email, so we generate that information to be sent. A transmitter is a device that takes that information and converts it into some signal that can be transmitted across our medium. We're going to spend several lectures talking about the structure of the different signals that can be sent across communication links. But think of a signal like an audio signal, some audio wave or some electrical signal across some copper wire. So we'll look at the details of the physical signals that can be transmitted. The transmitter takes the data, for example, the email and converts it into some, say, electrical signal to be sent across wires. Together we can say that's the source system. The source may be my computer, the transmitter may be a modem or a LAN card in my computer. It's all part of the source. That signal goes through our transmission system. A simple example of a transmission system may be a wire, a wire that carries an electrical signal. A more complex transmission system could be using different technologies like optical fiber and, in fact, can be an entire network, like the internet. We send some signal through a transmission system. The receiver is the device that takes the received signal and converts it back into data. For example, it takes some electricity that it receives and converts it back into zeros and ones which represent an email. And the destination consumes that data, they read it. For example, the receiver's computer is the destination. So we can look at communications from the perspective of these five blocks. We create information, transmit it. It goes through some transmission system and we receive it and consume it at the destination. Unfortunately, it's more complex than that. To get this to work in a variety of scenarios, what do we need to do at the source, at the transmitter? What does the transmission system need to do and what characteristics must it have? What should the receiver do? It's very, very complex. There are many things that need to be done. That's why we have an entire course looking at it. That's just my example that almost corresponds to those five blocks. A source, say, a computer, a PC that someone writes an email on, a modem in the old days, a dial-up modem, but now, say, an ADSL modem or a 3G USB card that plugs into a laptop or a wireless LAN transmitter, even, which takes some binary data and transmits a signal in this example through some telephone network and is received by another modem, which converts back and gets the binary data at a server, for example, a web server, an email server, or whatever is going to receive the data. So a simple model of communications contains those five blocks, but for communications to work effectively, what we need to do in each of those five blocks is very complex. There are many different tasks that are needed and we're going to spend this course going through those tasks. I'm not going to explain them to you now. Here's just a list of some of them. You will not understand some of these. Some examples to send data or a signal from one end point, one modem to another across a link, we may need to do multiple tasks, like have a scheme to generate the signal, what type of electrical signal or light signal do we transmit Unfortunately, in the real world, we may send something and we may have some interference or some errors in our transmission system, so we need to be able to detect any errors, correct them if possible, fix them. Why would we want to do that? Well, we said we need accurate transmission of our information for effective data communication. So error detection and correction will go through and spend several lectures on what that means and how is it achieved and flow control as well. When we're sending information, often we need to indicate the destination. We said delivery is the first measure of effective data communications. One way to ensure we deliver information to the right device is we use addresses. We give each device an address and when we send information, we say this information must go to this destination address. What are the structure of those addresses? Well, that needs to be defined somehow. You know, or you've seen IP addresses, 192.168.1.1 or similar addresses. So that's an example of addressing that's used in the internet. There are many others. When it comes to a large communication system like the internet, I want to send an email from my laptop to my friend in the US, then that message, that information needs to go through many different links to get to the US. There's not just one cable going from my laptop to my friend's computer in the US. There are many different links that connect us. And in fact, many different paths my information could take. My information could go through the internet that goes up to Hong Kong and then across Pacific to California. It could go the opposite direction through Europe and then across the Atlantic to the East Coast. And within those directions there are many different paths. Routing is the process of finding the best path. Find the path that delivers the information in an effective manner. After the midterm we'll spend some time on routing and routing protocols. And other things that need to be done and we're going to cover most of these or some of these in this semester. Security, we won't really cover this semester. Most of you will cover that next semester in CSS 322. When we talk about communications we can categorize the different technologies roughly based on whether we're doing data communications across a link. When I say a link, think of for example a cable from one computer directly to another or across a network. And a network is usually multiple links from one computer to another device, that device to another device and so on. There are different technologies and different issues that arise depending on whether we're focusing on an individual link or a set of links. So let's just give some quick examples of each of these categories. Data communications in this context is focusing mainly on a link. Although I don't have an example, I have two laptops here. Let's say I plug a cable into the LAN card of this laptop and connect it directly here. What do we need to do to get data from this laptop to this one? That's what we're focusing on here in data communications. To get information across a single link, for example. Well, that's where our model comes in. This is the same as the model before, these same five blocks. Just got an example of the different types of signals and information that we may have. For example, I want to send information across that link. Then the source, if it's some file or an email that I want to send, an email doesn't make sense direct between computers, but maybe I want to transfer a file, copy a file from one laptop to another. That file is just some text. The source may take that text and represent it as binary, zeros and ones, and pass it inside the computer, inside my laptop to the transmitter device. In my laptop, I have an inbuilt LAN card. The operating system passes it to the LAN card. We can think of some stream of bits of zeros and ones representing that text. Transmitter creates an electrical signal, an analog signal, and sends it through the transmission system. In my simple example of laptop to laptop, the transmission system is that one cable, a LAN cable. In more complex systems, there may be more things happening inside here. The receiver receives an electrical signal and does what it does, which converts it back to the text that can be consumed by the destination. Our first half of this course, basically up to the midterm, we're going to look at how do we generate, or what type of signals do we generate and transmit here across our transmission system, and how do we generate them? There are many different ways to take some zeros and ones, some bits, and create a signal to be sent. So that's what we're going to focus on for the first half of the semester. The transmission system, in a simple case, we can think of as a single cable or a single link, sometimes just a transmission line. The link between the transmitter and receiver is called a transmission line, the line or the system that we transmit our information across. What are some examples of links that I can have between my two laptops? Tell me some technologies. I can link just two laptops direct together. Bluetooth, LAN cable, the wired LAN cable. Anything else? There's different wireless technologies, ZigBee's a low-cost one. One you use every day. You use it in this building. What do you use? Wi-Fi or wireless LAN. Wi-Fi is another wireless technology. I could send information direct between laptops using a wired LAN or a LAN cable. You can actually use USB cable to connect them together. So many different ways I can connect those two laptops together. Many different types of links that I can have between the same transmitter and receiver. Some wired, some wireless. Some better than others. In which way are they better? Well, one thing that we care about is that if I want to get information from one computer to another, let's say the information is a small text file, 100 bytes, very small file, I want to send. If I send it using a wired LAN, wireless LAN, old laptops had infrared even. Infrared could send at a slow rate. Bluetooth, I can use Bluetooth on both laptops. A small file I can send quite quickly no matter what technology I use. So if it's a small amount of data, the link doesn't matter too much in most cases. What if I want to transfer, I've burnt 10 DVDs to here. So I have 50 gigabytes on one hard drive and I want to transfer 50 gigabytes to the other laptop. What about Bluetooth? Should I use that? Why not Bluetooth? Yeah, it's slow. If you've transferred information using Bluetooth, the speed at which you can send is about, it depends, it may be one megabit per second. I have 50 gigabytes or 50,000 megabytes or 400 megabits, 400,000 megabits, it would take me 400,000 seconds to transfer that information. So Bluetooth is no good because it's not fast enough. Or another way we'd say Bluetooth has some capacity, some limit at which you can send information. Different transmission lines may have different capacities, different speeds at which you can send using them. What about Wi-Fi? Would you do that? You could use Wi-Fi. The speed of Wi-Fi varies depending on device. On my old laptop, it's limited to 54 megabits per second, which is about 7 megabytes per second. But it's not even that good because it's a bit slower than that. So several megabytes per second, I can transfer. I've got 50,000 megabytes. Again, I have to wait a long time to transfer. Maybe a wire land would be better, 100 megabits per second or even 1,000 megabits per second. So different transmission lines have different capacities. The capacity, you think, is the upper limit of the speed or the amount of information we can send. So when we choose a transmission line, when you build a network, build a communication system, you need to choose a technology than you need to choose one that provides the required capacity. If my application is sending 100 bytes, it doesn't matter what you choose. If the application or the user wants to send 50 gigabytes across the network, then you need to be careful what you choose because the user's not going to be happy to wait for 10 or 20 hours to transfer that. So capacity is a common thing we care about. The maximum speed at which we can send with acceptable reliability. Reliability is about this accuracy, making sure that the information received is reliable, is an accurate representation of what was sent. Some systems or some technologies will be more reliable than others. You'll find that a wired LAN usually will be much more reliable than a wireless LAN because with wireless LAN, other people may be around interfering. And of course, we want to minimize cost. I could go out and buy a super-duper LAN card that supports 10 gigabytes per second, attach it to here, and then attach it to this computer and transfer at a very high speed. But of course, it costs me much more than the in-built LAN card, which is effectively free with a laptop. So choose a link or a transmission line that gives us good enough speed, required capacity, is reliable, but is cheap. Minimize our cost. Common things we need to consider. There's a topic on transmission media where we look at different wired and wireless media, like co-actual cable, twisted pair, like the LAN cables that you see everywhere, optical fiber, satellite transmission for wireless, a little bit about wireless LAN, and compare the different transmission lines or media. Some of the things we'll cover in those topics, we won't cover much, say much now, but some of the questions that we'll need to answer is if we've got information, some text, some file, we want to send some signal. How do we convert that information into a signal to send? What media to use? Do you use wireless or wired? What type of wires do you use? How do you encode information efficiently into a signal? What happens when there are errors? How do you deal with a case when many people want to transmit information at the same time, especially in wireless systems? So we'll cover some of these questions through this course. So that's a little bit about links. One computer direct to another. What about networks? Not much fun if I spend all my life just communicating with this other laptop. I would like to be able to communicate with a wider group of people and entities. And unfortunately I cannot have a cable going from my laptop to everyone else in the world or everyone else's computer. So we need networks. We'd like to be generally allow any user to communicate with any other user. Why limit? That would be the best, the ideal situation. To do that, we'll see that we'll need some communication software, some software that supports that, and we'll talk about that a little bit in the Internet, and different network technologies which in very simple way I'll classify as either wide area networks, WANs, or local area networks, LANs. They're not the only two types of networks, but two common ones which we'll see. Let's discuss those two first and then finish this lecture on the Internet. What's a wide area network? A network that covers a large geographical area. What's a network? Think of a network as a communication system that uses multiple links from one source to another computer device and then that other computer device has a link to another computer device and then another link, multiple links and then to the destination. So instead of just one link from source direct to destination when we need to go through multiple intermediate devices we call that a network and we need to do that because if we want to cover a large area and we don't have a direct connection we need to go via other devices. So what's a wide area network? A network that covers a large geographical area. Typically between cities, across cities, across Bangkok, maybe a company TOT is a large telecommunications company they have a wide area network covering Bangkok. They connect different sites across the city and they also have a network or technologies that connect Bangkok to other cities in Thailand so between cities in a country and some points in Thailand they connect to other countries either via underground or submarine cables, underwater cables underground optical fibres or even via satellite transmission. So wide area networks generally about communicating between cities, across cities, between countries, across the globe which differs from the next slide which is local area networks we'll see. Normally because they are large networks and to, let's say I need to lay some cabling across from here in Bankadee to Rungset. I want to connect them via some wide area network technology about 15, 12 or 15 kilometers. We want to connect our two sites together. We want to do it with some cabling. Unfortunately although SIT owns this building and this land or has access to it and owns the Rungset campus or through Tamasat we don't own all the land between our two campuses. Therefore we cannot just go in and dig a hole in the ground and lay some cable. So most wide area networks the network needs to cross public right of ways which means it crosses public land and other people's land and therefore to deploy and build that network takes a lot of negotiations time, money and effort because you need to get the permission of everyone in between to dig a hole through their land and lay a cable. It's not that simple but that's one of the issues with wide area networks. We'll see a local area network the alternative is usually owned and operated and built inside the same building and therefore the person who owns the building has the permission to lay the cables wherever they like. Therefore it's not cost effective for SIT to lay their own cables between our two campuses. So what do we do? We go to a telecommunications company that has already done it and we rent access from them. So the telecommunication companies sometimes called common carriers the large companies TOT, CAT the two government ones and many other companies Jasmine, True Corporation and so on they build the wide area networks across Bangkok and then we the users can rent access to their network and therefore the wide area networks normally carry data from multiple customers multiple organisations and these characteristics impact upon what technologies are used for wide area networks how fast they are how costly they are to deploy. Some of the issues that we would look at in wide area networks let's say TOT has a network connecting many points inside Bangkok and in fact inside Thailand we want to get data from one location to another there may be multiple different paths to take so finding the best path across the network is an important problem and the ways in which we get that data across the network we'll see we cover in the topic called switching, circuit and packet switching some technologies that you may see or cover ATM, it's not about money it's a technology asynchronous transfer mode for delivering data frame relay, SDH we in fact won't cover them in detail we just mentioned them as some examples so wide area network a network that covers a large geographical area between cities across cities between countries the other end point local area networks small coverage area inside your home office inside an office building maybe even a campus so a LAN so we have a LAN both wired and wireless inside this campus I have a LAN at home you may have a LAN at home so inside buildings, campuses, homes usually these networks are owned and operated by the organization owning the end devices or at least controlling the end devices so inside my home I own the computers that I'm connecting together and I own the network I bought the cables, I bought the devices that connect them together I maybe borrowed from an internet service provider but I have control over what I can use so the person who's using the network also owns the network in a wide area network usually the person who uses it SIT rents it from someone else a telecommunications company one other characteristic often when we can't compare LANs to wide area networks is that internally in the network the speed, the data rate or the capacity of the network of a LAN can be larger is usually larger than wide area networks per user what that means is an example of that is inside SIT the wired LAN is a capacity of 100 megabits per second 100 million bits per second is the minimum capacity well is the normal capacity it's in fact in some parts 1000 megabits per second 1 gigabit per second across the links but all of your traffic when you're web browsing in SIT goes through one link so everything when you're on the web visiting YouTube and you're inside SIT all of it goes through one link out to the internet from Bunker D out to the rest of the world that one link has a much lower capacity that wide area network link is much lower than 100 megabits per second especially lower than 1 gigabit per second it's about 20 megabits per second in fact that's not so correct we have multiple links for this campus we have a wireless link and a wired link but often the data rate available to each user is higher in a LAN than in a wide area network we'll talk a little bit about that when we cover the topic of LANs or talk about LANs local area networks later the reasons why examples, Ethernet or simply the LAN cable that you plug into your laptop you see the technology is called Ethernet and the one you use very common nowadays is wireless LAN or Wi-Fi is the marketing name so in terms of networks a broad classification is wide area networks local area networks and then if we want to communicate between any type of technology it doesn't matter if it's a wide area network or local area network we need some extra capabilities and that's what the internet provides us what's the internet well where did it come from maybe very briefly some history it came from what's this more than 40 years ago in the US and also in the UK to some extent and other countries the development from the US Department of Defense what was called ARPANET an experimental network connecting several sites in the US before we had the internet and that expanded to connect multiple universities and research organizations in the US and eventually expanded over the years to link together companies and across multiple countries and gets to what we have today is the internet before this time the major network for communications was the telephone network just the old telephone line where you pick up and you don't press numbers you spin the circle to dial the number anyone seen those phones some of you are too young so the old telephone network not your mobile phone just the old telephone network sometimes called the plain old telephone service that was the main type of communication the main form of communication network available and then the internet came along and they use different technologies telephone network use what's called circuit switching the internet uses packet switching and we'll have a topic on the difference between those two and the advantages and disadvantages the telephone network is still around today but starting to make use of packet switching through a major part of it the internet is defined by the set of what's called protocols that are used to transfer information between points and the two main protocols are called TCP and IP the transmission control protocol and the internet protocol maybe the most important is IP the internet protocol but there are many others associated as well so sometimes instead of the internet when we're looking at the technology people call it TCP IP IP networks or TCP IP we're going to look at those after the midterm and how they work so what is the internet? a simple description a collection of networks think of multiple wide area networks and local area networks all connected together and the one thing common about the devices in those networks is that they all use the internet protocol IP so I have a LAN inside my home we have a LAN inside this building we have a wide area network connecting this building to RungSit campus and across the RungSit campus many networks we connect them all together and if the PCs, the laptops and other devices in the network use this thing called the internet protocol then they may be able to communicate with each other and that larger network of connecting many smaller networks is called the internet or an internet the idea is that inside my home network I'm using wireless LAN here we're using wired LAN somewhere else we're using ATM we use different technologies in different networks the idea although we use different technologies providing they have IP in them that's the idea let's just have a quick look and see what we can skip over to finish this we won't go into detail of this example like that the elements in here but think of this as one LAN local area network here's a LAN with some computers connected via some device called a switch these are cables here's one LAN maybe this is at our campus here's another LAN at Runxit campus some other server mainframe it's an old picture but I say a server here some other location and these LANs are connected together via wired area networks so we have one LAN two three local area networks and one two wired area networks together there's one large network and we call that large network an internet and of course the internet that we use you can think that happens all across the world every network or many networks in the world are all connected together that's just a different view but we won't try to explain that one so very very quick introduction to some aspects of data communications mentioning some things which we're going to cover in the rest of the semester we'll get started on the details in the next lecture tomorrow and next week on the next topic in the last 30 minutes let's finish with there's two examples that I have here one is the SIT network I won't cover that we may cover that at another time one is the second example is the internet in Thailand it's a nice thing that I'll just introduce and you'll spend some time this week maybe tonight having a look at yourself because the pictures are quite difficult to see on the screen it's best to look at your own computer and zoom in but I'll show you a map of the internet inside Thailand in fact two different maps you can access from that website I'll just go to the website it's provided these maps are provided by Nectec Nectec is an organization part of NASDA at Science Park in Rangsit so they have a group that researches the internet and the structure of the internet in Thailand and they provide some maps of the current internet structure what month? okay and there's in fact a more recent one I've got one of May 2013 so they update a map of the internet inside this country and some other statistics some are a bit old though 2010 if you click on the link you'll see the maps that I've just I'm going to display there's one this is a map and you cannot see yet I'll zoom in I'll just show you the structure it's a map Thailand domestic internet exchange it's a map of the connections between the internet service providers inside Thailand the domestic ones the internet service providers are the companies that you and I pay money to to get internet access at home or SIT pays money to to get internet access to this campus or TAMASAP pays money to so these internet service providers normally have wide area networks across Bangkok across Thailand these blue ones on the outside zoom in and see the names in a moment the internet service providers inside the country you'll recognize some of their names the green ones I think are some government or research organizations they're not really commercial organizations but they also are part of the internet and the way the internet works in Thailand is that these local ISPs all have connections into what's called internet exchanges or national internet exchanges simply an internet exchange IX these internet exchanges there are different ones we see what 8 or 9 run by different companies the links a game we'll zoom in we'll show us which internet exchanges each ISP connects to and we'll also see the capacity or the speeds of those connections the internet exchanges CAT one of the government organizations ADC a commercial organization they are a large telecom company in Thailand BB I think they're associated I cannot remember this one CSL is CS locks info you may have heard of them Jasmine, Jasmine telecommunications Jastel I can't remember SPN TCCT is some Thai Thai charion something something owned by the guy who owns Thai Bev Thai beverages True internet gateway, TIG and TOT the other government telecommunications so these organizations run what's called internet exchanges when you and I subscribe to an ISP think as here you are with your computer you subscribe and say you have ADSL from your home and it connects into the ISPs network so you can think here you are and if I subscribe to this ISP I have a link into their network when I want to send data to someone else inside Thailand someone else who's subscribed to this ISP for example I send it to my ISP it goes via one of these lines to an internet exchange and then goes to the destination ISP and then to the destination user that's one way you can think of this map of course you see the lines it's much more complex there are multiple links between internet exchanges and ISPs a little bit better so here are some of the names of the local ISPs the companies that some of us we can subscribe to pay as a customer some of you will recognize some of you may not I think DTAC is down here some may be not for end users like you and I some may be just selling to businesses so you may not recognize them all CSLOCKSINFO who else is there NTT is the Japanese Proan is a large one and we see the links that they have say the CAT internet exchange and these are the capacities of the links or at least the sum of the link capacities for example LOXLEY has a 200 megabit per second link going up here if we follow that line here's a 1 gigabit per second link 12 gigabits per second link from KIP or links here and we see the different capacities that different ISPs have again this is much better if you analyze on your own computer you can look at different parts of it in enough detail and some will have links into multiple internet exchanges so I subscribe to TOT I pay them a monthly amount to use access the internet via them so I connect via this ISP and they have connections to multiple internet exchanges and we up to TOT to choose which one to send my data over depending upon cost and performance you can see a wide variation in the speeds 200 megabits per second for this one 22 gigabits per second 60 gigabits per second so remember you should know gigabit is a thousand megabits of course life may not be so much fun if we just communicate inside one country we want to communicate on the internet to the rest of the world this just shows the domestic internet there's another map showing the international connections let's bring it up same structure except these the blue ones are our national or domestic ISPs these are not national exchanges they are international gateways or international exchanges IIG which means these connect from local ISPs to foreign ISPs ISPs in other countries so these grey ones on the outside when we zoom in we'll see these are ISPs in other countries neighboring countries different places in the world and the links between them similar companies here operate their international gateways CAT, TOT, Jasmine and so on let's zoom in on some of the some of the foreign ISPs some you may recognize the names most you may not but you can pick out some of the countries Hong Kong, Singapore you probably know this one are they an ISP? well not really I said these are internet service providers think of an ISP as someone you pay for or a company pays to access the internet via but also we have some what's called content providers large companies that offer a lot of content on the internet Google what is the content that they offer all their services like search, Gmail documents and so on and the big one being YouTube Google owns YouTube so all the people who access Google content Google actually has sites in countries across the world so that when we access it from inside Thailand we don't have to access the content in the US where Google are based but we can access the content in Singapore or in Malaysia closer and having faster links means it's much faster for the end user so it's not just internet service providers it's also some large companies you'll see Microsoft, Yahoo in there Facebook and others Indosat in Indonesia Korea Telecom Microsoft in Singapore so you see the 10 gigabit per second link from one Thai gateway to Microsoft in Singapore in Hong Kong NTT in Hong Kong in Japan, Singapore and so on not Japan there so show some of the connectivity between the large organisations inside this country and outside this country I won't show any more details there it's again worth you looking in your own time to just explore that and you can see where the links go and what are the different ISPs and some other statistics one one last thing if we sum up all of the links going inside Thailand to the outside we sum them all up the total international bandwidth is 507 gigabits per second so the sum of all of those links essentially well that means in theory going out of the country everyone could be sending from Thailand out at 507 gigabits per second that's the capacity for the international bandwidth about 5 I arrived here in 2006 and when I first looked at this it was about 10 gigabits per second so it's increased rapidly over the last 5 or 6 years from 10 gigabits per second 50 times larger 500 gigabits per second so it's increasing rapidly each year the number of links inside and outside of Thailand have a look at them in your own time no questions about them it's just a thing of interest that you may have a look at and learn a bit more that's enough for our lecture I just want to go through some admin things any questions before I do that any technical questions not about the structure but about the topic AS numbers against pairing DV no so you can see who pairs promiscuously with other numbers yeah no I haven't I'm going to do that tomorrow okay easy alright good you'll be fine in the quiz