chelloacademy participant s workbook Internet Traffic A module explaining the flow of traffic over the Internet :-)

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1 chelloacademy participant s workbook Internet Traffic A module explaining the flow of traffic over the Internet :-) 1

2 Before you start Internet traffic The Internet traffic techno chello module is part of the Internet technologies course from the chelloacademy techno chello universal curriculum. In combination with this module you should also sit the following modules in order to complete the course: - DNS - Proxy The Internet technologies course is aimed at chello helpdesk agents and installation engineers (according to affiliate requirements). For further details of this and other chelloacademy technology courses please consult chelloacademy online at: Other chelloacademy technology courses include: - Network fundamentals - Internet services - Operating systems - Security Using this booklet This Participant s Workbook has been developed by chelloacademy to accompany a classroom, or online, training module. It recapitulates the content covered in classroom/online training, giving detailed information and Internet resources for further reading. For optimal presentation and use of this workbook we have included the following to mark information of special interest to the reader: Geek box Geek boxes contain information, which goes deeper than the required understanding of the module s content. Use geek boxes when you feel confident enough to move on from the standard content, or when you want to know more Test yourself Test yourself boxes give you the opportunity to test your understanding of the subject you have been reading about. Answers can be found at the back of the workbook If you have this workbook, but have not yet sat the related classroom, or online training please speak with your supervisor to arrange the scheduling of this training. 2

3 Contents Before you start...2 Content...3 Introduction...4 Network traffic...5 Capacity...6 Volume...6 Working with the numbers...6 Working with the numbers...7 Bandwidth...7 Bandwidth...8 Line capacity...9 Response time...10 Quick reference...11 On the Internet...12 National traffic...14 National exchanges...15 Peering...16 International traffic...17 International peering...17 AORTA...18 Test yourself...20 Recap...22 Links...23 Test yourself answers

4 Introduction The Internet, in a simple definition, is a collection of cables (networks) transporting and transferring data packets at extremely high speeds. Also known as the information super highway, in many ways the Internet can be seen as an immense road system with data traveling throughout it like cars. As we start to see the Internet in this fashion you can imagine the complexity involved as it grows to span the entire globe, imagine the strains placed on the system as its load and congestion increases. In an ever-demanding world, where end to end speed of network transfers is becoming increasingly critical and the reliability of connections and routing need to hold up to a seemingly ever-increasing load traveling over and ever-expanding network we have to wonder what is keeping the Internet together? How is the traffic directed and who is building all the roads...? Objectives! Associate the Internet traffic and the information circulation! Define volume and capacity! define bandwidth! Define latency (response time)! Explain the causes of latency (response time)! Define peering! Explain the AORTA Keywords Capacity Volume Bandwidth Latency Bit Byte Traffic Exchange Peering AORTA Response time 4

5 Network traffic Just like driving from point A to point B, when we send data over the roads of the Internet it takes a certain amount of time to arrive at its destination. If you are in a car, then how long it takes to arrive would depend on: - how direct the route you take is (the distance you have to travel) - how congested the roads are - the speed at which you drive (this one is really important) Similar things affect the time taken to transfer data between points on a network, but, as we will find out in the course of this module, the word speed is a very ambiguous one when we are talking about networks. There are four things which have an effect on the apparent speed of a network transfer, these are: - capacity - volume - bandwidth - latency Each can have a varying effect on the apparent speed, depending on how the network is being used. Even the numbers used to show the speed of transfer can be misleading if you don t understand the acronyms stating what they explain. So, keeping this in mind, lets start at the beginning with capacity and volume. 5

6 Capacity Capacity is a very important term when it comes to computers, as every device which holds, or transmits, data has a capacity that is, a maximum amount of data which it can hold at one time. Let s make sure we re clear about this: Capacity: The maximum amount that can be contained On a network, data transfer is real time and capacity is constantly being filled and emptied and re-used and re-emptied capacity usage on a network is constantly varying. Therefore, a network connection with a high capacity has the capacity to carry large amounts of data simultaneously. The important point to remember here is that when we refer to capacity we are actually referring to the total possible amount of data that can be held/handled at any given point by any media from a CD to a network cable Volume Volume is another term used to define amounts of data, but it is important to note that volume is not the same as capacity. When we refer to data volume we refer to the actual amount of data there is, rather than the amount there possibly could be. Imagine you have a measuring jug that can measure amounts of up to 1 litre. This means the jug has a capacity of 1 liter. If you fill the jug with water to the point of 400ml the jug still has a capacity of 1 liter, but the volume of water in the jug is only 400ml. Volume: The actual amount that is contained The same principals apply to volume and capacity definitions for data transfer/storage, the main difference being when we talk about networks and data transfer (rather than storage) the volume of data present is constantly changing Remember this!! Capacity is the maximum amount which can be held at any given moment! Volume refers to the actual amount that is contained! On a network, data transfer is real time and capacity is constantly being filled and emptied and re-used and re-emptied volume usage on a network is constantly varying. 6

7 Working with the numbers All computer hardware is measured and labeled according to its speed (how many bits it can handle in a second) and/or capacity (how many bytes it can hold simultaneously) that counts from floppy disks to network cables. NOTE! bits and bytes are not the same thing! bit (binary digit) The smallest unit of data possible, a bit is simply a 1, or a 0. You can t express much in that, so bits are joined together to make bytes. Byte (binary term) A byte consists of eight bits and is used as a description of capacity, while bits are generally used when speaking about speed. Every measurement (number) will be followed by an acronym, depicting exactly what has been measured - this is what adds meaning to the value. With regard to computers and networks, these are the abbreviations you need to know: - capacity and volume KB (kilobytes) MB (megabytes) bytes (just to be awkward) - 1,048,576 bytes (2 20 ), or 1024 KB GB (gigabytes) - 1,073,741,824 bytes (2 30 ), or 1024 MB TB (terabytes) - 1,099,511,627,776 bytes (2 40 ), or 1024 GB - speed kbps (kilobits per second) - units of 1000 bits per second KB/s (kilobytes /second) - units of 1024 bytes per second mbps (megabits per second) - units of 1,000,000 bits per second MB/s (megabytes /second) - units of 1,048,576 bytes per second MHz (megahertz) - unit expressing 1,000,000 cycles per second Remember this!! 1 byte = 8 bits! Speed is generally measured in bits! Capacity and volume are generally measured in bytes! 1kb (kilobit) = 1000 bits and so on! 1KB (kilobyte) = 1024 bytes and so on 7

8 Bandwidth You are maybe beginning to understand that when we speak about high bandwidth we do not mean high speed, although that is what many people may believe and the two things are related to an extent. When we speak about high bandwidth we mean a high capacity for data transfer the possibility of transferring larger amounts of data simultaneously. Inevitably, the more data which can be transferred in one go, the quicker a file will arrive at its destination and so the faster the end to end transfer time is. However, this does not mean the individual data packets actually travel at a faster speed over the network. Here s a good example to illustrate this: Would you say that a Boeing 747 is three times "faster" than a Boeing 737? Of course not. They both cruise at around 500 miles per hour. The difference is that the 747 carries 500 passengers where as the 737 only carries 150. The Boeing 747 is three times bigger than the Boeing 737, not faster. Now, if you wanted to fly from New York to London, the Boeing 747 is not going to get you there three times faster. It will take just as long as the 737. In fact, if you were really in a hurry to get to London quickly, you'd take Concorde, which cruises around 1350 miles per hour. It only seats 100 passengers though, so it's actually the smallest of the three. Size and speed are not the same thing. On the other hand, If you had to transport 1500 people and you only had one aeroplane to do it, the 747 could do it in three trips where the 737 would take ten, so you might say the Boeing 747 can transport large numbers of people three times faster than a Boeing 737, but you would never say that a Boeing 747 is three times faster than a Boeing 737. The question is not of how fast data can be transferred, but how much data can be transferred simultaneously and how much data our hardware (such as a cable modem) is able to send/receive simultaneously. We never want to know how quickly we can send one packet of data between two points, but how quickly we can send a file (multiple packets of data) between them. Ok, so now we really understand that bandwidth is more about the size (or capacity) of a connection than its actual speed. Remember this!! High bandwidth = high capacity! Low bandwidth = low capacity 8

9 Line capacity There are some standard names used for describing high capacity network cables also known as lines. These are not the kind of cables you have lying around your house, but rather the type that might be used to connect Italy with Spain. Here is a brief description of the most common: STM-1 STM stands for Synchronous Transfer Module STM-1 lines have a capacity of 155mbps E1 E1 (or E-1) is a European digital transmission format devised by the ITU-T. It's the equivalent of the North American T-1 format. E2 through E5 are carriers in increasing multiples of the E1 format, although E1 and E3 are the ones we will refer to most. E1 lines have a capacity of Mbps E3 E3 lines have a capacity of Mbps. Fibre optic Fibre optic cables are contain a bundle of glass (or plastic) threads (fibers) which transmit data using light. Generally used for long distance connections, the advantages of using fibre optic cables include: - the bandwidth is higher than that available through metal cables - digital data being transferred through fibre optic cables is less likely to be corrupted (less interference) than when transferred through standard metal cables NOTE! fibre optic is a type of cable and does not refer to the capacity of the connection. DWDM Dense Wave Division Multiplexing Dense wave division multiplexing refers to the process of dividing a single beam of light into a number of colour beams as it travels through a fibre-optic cable. Each colour beam on its own has the same transmission capacity as the original, unsplit, beam of light, thus significantly enhancing transmission capacity. T1 T1 is the American equivalent of the European E1 standard. T1 lines use copper wire and span distances within and between major metropolitan areas. T2 and T3 are multiples of the T1 format, although T1 and T3 will be referred to most. T1 lines have a capacity of Mbps T3 T3 lines have a capacity of Mbps 9

10 Response time One other, often overlooked, factor of network performance is response time (or latency) - this refers to the time taken for hardware to respond after receiving a request. The response time encountered by data traveling over a network can have a major effect on the overall performance. Imagine the size of the Internet as a whole and how many times a data packet traveling through the network will need to be received, processed and forwarded by hardware that can be routers, servers, switches, modems etc every time this equipment needs to work with the data a certain amount of time passes and the data packet is stalled, slowing down it s end to end transfer speed. What s more, you can t reduce the response time of a device, so if you encounter bad response times you can only improve it by installing new equipment. If you are just transferring files over a network you re not going to notice this delay imposed by the hardware it will account for a very small percentage of the total transfer time. So, when does response time really matter? There is a minimum amount of response time on a network this is the minimum delay time created by the hardware between two given points. While this may be a small proportion of the time taken for transferring large amounts of data, sending small amounts of data over the network will not reduce the minimum latency and it will become a higher proportion of the overall transfer time. A 100ms response time (such as that on older analog modems) will cause a noticeable delay/echo in audio transmissions, it would also make online games appear sluggish. It won t matter how high the capacity/bandwidth is it just takes a minimum amount of time for the smallest piece of data to cross the network. What can you do to improve response time? you can do nothing compression will make the data smaller, but response time is not effected by the amount of data sent. You could get multiple connections, but it s not about the amount you can send, it s about the delay applied to each packet. The only solution is to use hardware which has a lower response time. Remember this!! Response time is the shortest possible time it will take for hardware to receive a request, process it and pass it on to the next piece of hardware! Response time is measured in milliseconds! Response time will only affect the speed of a connection which requires the sending of repeated small amounts of data (such as video streaming, or online gaming) 10

11 Quick reference To recap what we have covered so far: definition unit Capacity The maximum amount of data that can be held at one time Bytes KB MB GB TB Volume The actual amount of data which is being held Bytes KB MB GB TB Bandwidth The capacity of a network connection High Low (no unit) Response time The minimum amount of time it will take for hardware to process and respond to a request ms (mili-second) Speed The amount of time taken to transfer data over a network connection bps Kbps Mbps Gbps 11

12 On the Internet The Internet is a huge global network made up of many smaller networks. One division, which can easily be seen in the global Internet structure, is between national sites and international ones. Lets look at that a little further: National Internet The national section of the Internet is the part of the Internet which is hosted in the same country as you are accessing the Internet from. i.e. the section of the Internet you can access without needing to make an International connection. ` National Internet sites are often in the national language, so if you access the Internet from a country other than your home country you are unlikely to access the national Internet. NOTE! If you are English and access the Internet from England, then the Internet sites being hosted in England comprise the national Internet HOWEVER If you are English and access the Internet from Spain (say, whilst on holiday), then the Internet sites being hosted in Spain comprise the national Internet. International Internet The international section of the Internet is EVERYTHING connected to the Internet outside of the country you are accessing the Internet from. i.e. If you are English and access the Internet from Spain (say, whilst on holiday) and go to the website of your favourite English newspaper (say then, even though the site is English and you are English) you will be accessing the International Internet. 12

13 Remember this!! The Internet is a collection of connected networks all over the world! There Internet can easily be split into national and international sections! The national Internet is within the country from where you are accessing the Internet! The international Internet is outside the country from where you are accessing the Internet points 13

14 National traffic The top level of domains (that s the name/address you use to access a website) is the national level, so you can tell which national network you are using simply by the domain name you are accessing. Geek Box - domain names Domain names are the addresses you type into your web browser when you wish to access a website, or (more precisely) the bit after in an address: e.g. gareth@chello.com the dots separate levels in the domain name, with the highest being on the right (.com in this case) is known as the top level domain. It seems obvious that using the national Internet for the country you are in should be smoother and quicker than if you were to access the national domain of a different country there is simply less distance for the data to travel. Even so, the quality of the network you are using is still of very great importance and the connection of networks doesn t end on a national level, we can now make another division on the level of cities. Although city network divisions are not specified in domain names, if we are to imagine the structure of wires which must exist for the Internet to function, within a country the main points of connection would logically be situated in the major cities. This interconnection could soon become a mess if the transfer of data isn t correctly organized and monitored. 14

15 National exchanges The Internet is so called because it is an INTER-connected NET-work, comprising many individual networks connected at important and/or logical points. If you imagine trying to send data across this amalgamation of networks spanning the city, country, or globe you can understand that a structure needs to be in place for handling the sharing/exchanging of data. Although we see the Internet as a single entity it is not that way at all. To create the Internet from these individual network segments you need to have connection points places where the networks can meet and exchange data in a structured manner. These points are known as Internet exchanges (IX for short). Each national network (or ISP) will have a route for sending traffic internationally, but may only cover a specific national area. Without national exchanges, national traffic would end up being routed internationally (to re-enter a country at a point which is connected to the destination network). This is not a viable solution because: - it is expensive - it is slower than sending data on the most direct route - it would place an unnecesary strain on international connections which are needed for real international traffic. 15

16 To illustrate this, lets pretend this big rectangle is a country requiring Internet access (Geekland) and the other boxes are adjacent countries (Nerdway and Asciia). Imagine the routing differences if the IX was not present for someone on network 4 to contact someone on Network 1 they would need to send their data through Nerdway and so on Peering What is peering? Interconnect agreements between ISPs - allowing traffic to flow over each other s network - are known as peering agreements. At the start of the Internet age no money changed hands for such agreements, but recently larger ISPs have started charging smaller ISPs for using their facilities. All large ISPs develop a peering policy setting out the circumstances, rules and arrangements governing peering with other types of network and for various types of traffic. Based on the Nerdway example: if someone connected to network 4 wanted to contact someone in asciia then the most direct route would be to send the data via the IX and over either network 3 or network 2. However, if no peering agreement has been made between the owners of network 4 and the owners of network 2 and/or 3 this will not be possible and the data will have to travel via Nerdway. Remember this!! National networks are generally interconnected in major cities at points called Internet exchanges (IX)! National peering agreements allow different ISPs to share network capacity and connections within a country 16

17 International traffic When you want to send traffic internationally using the Internet the situation becomes a little more complicated. The basic principles of data transfer remain the same, but the distance traveled is probably much greater and the data will probably need to pass through a larger number of connection points to reach its destination. It is also possible that there is no direct connection from the origin of a request to its physical destination, so the data may have to pass through multiple countries to get there. If you imagine the cost of laying network cables nationally compared to that of laying them internationally we can see that peering on an international scale is even more appealing than that for national connections. International peering It is again important to remember that the Internet is not, physically, one single object, but rather a collection of individual sections all agreeing to work together. As national peering agreements are required to ensure optimal data flow via IXs and competitor s networks, International peering agreements allow countries to send data across another country s network structure. Remember this!! International traffic travels across top level domains! International peering agreements allow ISPs to share network capacity and coverage on a global scale 17

18 AORTA AORTA is chello's own backbone. So what is a backbone, I hear you ask! If you think of the Internet as a road network, a backbone is an eight-lane motorway. It is a connection (usually a group of high speed fibre optic cables) with a capacity high enough to carry large volumes of data over long distances. Many people divide the Internet into transport networks and distribution networks. Distribution networks are the networks linking the ISPs with their customers, while transport networks, like chello s AORTA, link the ISPs. You can also use the term "backbone" in the context of LANs. In this case, it is a supply line, or lines, connected two parts of the LAN, for example in different buildings. AORTA May 2001 Geek Box - AORTA Here are some more AORTA facts: AORTA currently spans twelve countries and four continents (The Netherlands, UK, Belgium, France, Germany, Austria, Norway, Sweden, US, Chile) AORTA is designed to provide sufficient connectivity points as to eliminate customer impact during failure of one of its elements. Dual protected fibre routes as well as redundant hardware design is used for fault protection AORTA is built utilizing an optical protected ring structure. All optical layer is leased on a combination of one to three year leases and ten to twenty five year IRU s The IP layer is managed utilizing GSR and 7500 series Cisco routers AORTA is designed hierarchically, based on a three layer approach. These layers are the Core, Distribution and Access layers. Each critical element is duplicated to increase the reliability. CORE Distribution Layer Access Layer Affiliate Level provides the inter-area traffic provides the intra-area traffic provides the inter-domain traffic provides the local access or last mile connectivity 18

19 Remember this!! Some ISPs have their own backbone this is a central core network, which can be smaller scale (national), or larger scale (international)! chello has its own International backbone known as AORTA 19

20 Test yourself 1. Join the terms and descriptions: volume capacity bandwidth speed capacity per second actual amount contained possible amount which can be contained capacity of a network conection 2. 1 byte is equal to: a. 8 MB b. 4 bits c. 4 TB d. 8 bits 3. Speed is generally measured in: a. bits per seconds b. bytes per seconds c. KHz d. revolutions 4. 1 KiloByte (KB) is equal to: a bytes b bits c bytes d bits 5. Join the terms with their description: high bandwidth high capacity low bandwidth low capacity 6. Response time is the time taken for what to respond? a. modems b. routers c. switches d. all of the above 7. Response time can be improved by: a. upgrading software on the problem device b. changing cables to and from the problem device c. replacing the problem device d. sending smaller packets of data through the problem device 8. Bad response time will be most noticeable when: a. sending s b. video streaming c. downloading software d. burning CDs 9. The capacity of an STM-1 line is: a. 100 mbps b. 155 mbps c. 200 mbps d. 255 mbps 20

21 10. National Internet sites can be recognized by: a. the top level domain b. the language of the pages c. the IX you are using d. all of the above 11. IX stands for: a. Internet expansion b. Invalid example c. Internet exchange d. Intra-eXchange 12. Interconnect agreements between ISPs are known as: a. network share agreements b. peering agreements c. traffic swap agreements d. join-and-exchange 13. The term backbone is used to describe: a. the shortest route for network data to travel between two common points b. a high speed, International network, usually owned by an ISP c. the users on a network d. all of the above 21

22 Recap In this module we have covered the following main points: Network traffic Capacity! Capacity is the maximum amount which can be held at any given moment! On a network data transfer is real time and capacity is constantly being filled and emptied and re-used and re-emptied volume usage on a network is constantly varying Volume! Volume refers to the actual amount that is contained Working with the numbers! 1 byte = 8 bits! speed is generally measured in bits! capacity and volume are generally measured in bytes! 1kb (kilobit) = 1000 bits and so on! 1KB (kilobyte) = 1024 bytes and so on Bandwidth! High bandwidth = high capacity! Low bandwidth = low capacity Response time! Response time is the shortest possible time it will take for hardware to receive a request, process it and pass it on to the next piece of hardware! Response time is measured in milliseconds! Response time will only affect the speed of a connection which requires the sending of repeated small amounts of data (such as video streaming, or online gaming) On the Internet Introduction! The Internet is a collection of connected networks all over the world! The Internet can be broken down into smaller and smaller sections using top level domains this is done on a national level! The national Internet is within the country from where you are accessing the Internet! The international Internet is outside the country from where you are accessing the Internet National traffic! National networks are generally interconnected in major cities at points called Internet exchanges (IX)! National peering agreements allow different ISPs to share network capacity and connections within a country International traffic! International traffic travels across top level domains! International peering agreements allow ISPs to share network capacity and coverage on a global scale! Some ISPs have their own backbone this is a central core network, which can be smaller scale (national), or larger scale (international)! chello has its own International backbone known as AORTA 22

23 Links If you have enjoyed learning about networking and would like to look further into the subject here s some links which you may find interesting. Remember the Internet is a great resource and there s plenty more information out there! Additional reading! find a backbone! this site details available international backbones and bandwidth, along with various other interesting ISPdetails. References in this workbook!

24 Test yourself answers Here you can find answers to all the questions posed in the test yourself sections of this workbook. If you have any questions regarding these answers please contact your trainer. Thanks for learning with chelloacademy :) 1. Join the terms and descriptions: volume capacity bandwidth speed capacity per second actual amount contained possible amount which can be contained capacity of a network conection 2. 1 byte is equal to: d, 8 bits 3. Speed is generally measured in: a, bits per second 4. 1 KiloByte (KB) is equal to: c, 1024 bytes 5. Join the terms with their description: high bandwidth low bandwidth high capacity low capacity 6. Response time is the time taken for what to respond? d, all of the above 7. Response time can be improved by: c, replacing the problem device 8. Bad response time will be most noticeable when: b, video streaming 9. The capacity of an STM-1 line is: b, 155 mbps 10. National Internet sites can be recognized by: a, the top level domain 11. IX stands for: c, Internet exchange 12. Interconnect agreements between ISPs are known as: b, peering agreements 13. The term backbone is used to describe: b, a high speed, International network, usually owned by an ISP 24