Internet Infrastructure 26 Jan 2004 3
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This document provides an overview of the infrastructure of the information super highway. It discusses how the internet is a collection of networks connected through various means such as domain name servers, network access points, backbones, and protocols. It describes how internet service providers (ISPs) connect computers to the internet and how large communications companies provide wholesale connections between ISPs. The document also discusses concepts like routers, which determine where to send information, and network access points, which allow different networks to interconnect.
Internet Infrastructure 26 Jan 2004 3
- 1. Infrastructure of the Information Super Highway 26 January 2004 For PIMSAT By : Khawar Nehal Applied Technology Research Center khawar.nehal@atrc.net.pk 923332486216 922138180991
- 2. No one owns the Internet. It is collection of networks. The name was derived from the collection. Started in 1969 with 4 hosts. Monitored by The Internet Society www.isoc.org which was created in 1992
- 4. You will learn about domain name servers network access points backbones and how your computer connect to the Internet.
- 5. The connectivity options are : Dialup, ISDN, LAN, WLAN, V.35 Radio, VSAT, DVB Satellite, DSL, GSM, Satellite Modem, GPRS, UMTS, Bluetooth, Infrared, or any other way two computers can communicate. Basically all you need is an implementation of the TCP/IP protocol from your computer to the other computer connected to the Internet.
- 6. To make it easier to find a computer connected to the Internet, ISPs came in to provide a commercial service. The ISPs charge to have your computer connected to their computers. The ISPs help connect lots of computers to the internet simultaneously. http://127.0.0.1/connect.swf
- 7. The ISPs get one or more connections from large communications companies. The large communications companies sort of provide a whole sale connection service for ISPs. The large companies own or rent satellites and fiber connectivity worldwide. Instead of having just one large connection between large companies there are several. http://127.0.0.1/routerinet.swf
- 9. Example HK Telecom wants to connect to British Telecom. They can have three fiber connections going through the middle east, Europe, and one through the US. Along with a satellite or two to back that up.
- 10. Imagine that Company A is a large ISP. In each major city, Company A has a Point o Presence (POP) The POP in each city is a rack full of modems that the ISP's customers dial into. Company A leases fiber optic lines from the phone company to connect the POPs together
- 11. Imagine that Company B is a corporate ISP. Company B builds large buildings in major cities and corporations locate their Internet server machines in these buildings. Company B is such a large company that it runs its own fiber optic lines between its buildings so that they are all interconnected.
- 12. In this arrangement, all of Company A's customers can talk to each other, and all of Company B's customers can talk to each other, but there is no way for Company A's customers and Company B's customers to intercommunicate. Therefore, Company A and Company B both agree to connect to Network Access Points (NAPs) in various cities, and traffic between the two companies flows between the networks at the NAPs.
- 13. Network Access Points are also known as network peering points. In the real Internet, dozens of large Internet providers interconnect at NAPs in various cities, and trillions of bytes of data flow between the individual networks at these points.
- 14. Bridging The Divide All of these networks rely on NAPs, backbones and routers to talk to each other. What is incredible about this process is that a message can leave one computer and travel halfway across the world through several different networks and arrive at another computer in a fraction of a second!
- 16. Routers Routers are specialized computers that send your messages and those of every other Internet user speeding to their destinations along thousands of pathways.
- 17. Routers A router has two separate, but related, jobs: * It ensures that information doesn't go where it's not needed. This is crucial for keeping large volumes of data from clogging the connections of "innocent bystanders." * It makes sure that information does make it to the intended destination.
- 18. Routers In performing these two jobs, a router is extremely useful in dealing with two separate computer networks. It joins the two networks, passing information from one to the other. It also protects the networks from one another, preventing the traffic on one from unnecessarily spilling over to the other.
- 19. Routers Regardless of how many networks are attached, the basic operation and function of the router remains the same. Since the Internet is one huge network made up of tens of thousands of smaller networks, its use of routers is an absolute necessity. http://127.0.0.1/routerlan.swf
- 20. NSF The National Science Foundation (NSF) created the first highspeed backbone in 1987. Called NSFNET, it was a T1 line that connected 170 smaller networks together and operated at 1.544 Mbps (million bits per second).
- 21. Commercial Providers IBM, MCI and Merit worked with NSF to create the backbone and developed a T3 (45 Mbps) backbone the following year.
- 22. Backbones Backbones are typically fiber optic trunk lines. The trunk line has multiple fiber optic cables combined together to increase the capacity. Fiber optic cables are designated OC for optical carrier, such as OC3, OC12 or OC48. An OC3 line is capable of transmitting 155 Mbps while an OC 48 can transmit 2,488 Mbps (2.488 Gbps).
- 24. Today Today there are many companies that operate their own highcapacity backbones, and all of them interconnect at various NAPs around the world. In this way, everyone on the Internet, no matter where they are and what company they use, is able to talk to everyone else on the planet.
- 26. Protocols Every machine on the Internet has a unique identifying number, called an IP Address. The IP stands for Internet Protocol, which is the language that computers use to communicate over the Internet.
- 29. IP Address To make it easier for us humans to remember, IP addresses are normally expressed in decimal format as a dotted decimal number like the one above. But computers communicate in binary form. Look at the same IP address in binary: 11011000.00011011.00111101.10001001
- 30. IP Address The four numbers in an IP address are called octets, because they each have eight positions when viewed in binary form. If you add all the positions together, you get 32, which is why IP addresses are considered 32bit numbers.
- 31. IP Address Since each of the eight positions can have two different states (1 or zero), the total number of possible combinations per octet is 28 or 256. So each octet can contain any value between zero and 255. Combine the four octets and you get 232 or a possible 4,294,967,296 unique values!
- 32. IP Address Restrictions Out of the almost 4.3 billion possible combinations, certain values are restricted from use as typical IP addresses. For example, the IP address 0.0.0.0 is reserved for the default network and the address 255.255.255.255 is used for broadcasts.
- 33. IP Address Classes The octets serve a purpose other than simply separating the numbers. They are used to create classes of IP addresses that can be assigned to a particular business, government or other entity based on size and need.
- 34. IP Address Classes The octets are split into two sections: Net and Host. The Net section always contains the first octet. It is used to identify the network that a computer belongs to. Host (sometimes referred to as Node) identifies the actual computer on the network.
- 36. Before DNS When the Internet was in its infancy, it consisted of a small number of computers hooked together with modems and telephone lines. You could only make connections by providing the IP address of the computer you wanted to establish a link with.
- 37. Before DNS For example, a typical IP address might be 216.27.22.162. This was fine when there were only a few hosts out there, but it became unwieldy as more and more systems came online.
- 38. The /etc/hosts file The first solution to the problem was a simple text file maintained by the Network Information Center that mapped names to IP addresses. Soon this text file became so large it was too cumbersome to manage.
- 39. The DNS In 1983, the University of Wisconsin created the Domain Name System (DNS), which maps text names to IP addresses automatically. This way you only need to remember the domain name of the site like yahoo.com instead of the IP address.
- 42. Top Level Domains Toplevel domain names, also called firstlevel domain names, include .COM, .ORG, .NET, .EDU, .GOV, .MIL, .PK, .INT, and a few hundred more. Within every toplevel domain there is a huge list of secondlevel domains. For example, in the .COM firstlevel domain there is: yahoo.com
- 43. Top Level Domains Every name in the .COM toplevel domain must be unique. The leftmost word, like www, is the host name. It specifies the name of a specific machine (with a specific IP address) in a domain. A given domain can, potentially, contain millions of host names as long as they are all unique within that domain.
- 44. Top Level Domains DNS servers accept requests from programs and other name servers to convert domain names into IP addresses. When a request comes in, the DNS server can do one of four things with it:
- 45. Top Level Domains # It can answer the request with an IP address because it already knows the IP address for the requested domain. # It can contact another DNS server and try to find the IP address for the name requested. It may have to do this multiple times.
- 46. Top Level Domains # It can say, "I don't know the IP address for the domain you requested, but here's the IP address for a DNS server that knows more than I do." # It can return an error message because the requested domain name is invalid or does not exist.
- 47. Top Level Domains Let's say that you type the URL www.yahoo.com into your browser. The browser contacts a DNS server to get the IP address. A DNS server would start its search for an IP address by contacting one of the root DNS servers.
- 48. Top Level Domains The root servers know the IP addresses for all of the DNS servers that handle the toplevel domains (.COM, .NET, .ORG, etc.). Your DNS server would ask the root for www.yahoo.com, and the root would say, "I don't know the IP address for www.yahoo.com, but here's the IP address for the .COM DNS server."
- 49. Top Level Domains Your name server then sends a query to the .COM DNS server asking it if it knows the IP address for www.yahoo.com. The DNS server for the COM domain knows the IP addresses for the name servers handling the www.yahoo.com domain, so it returns those.
- 50. Top Level Domains Your name server then contacts the DNS server for www.yahoo.com and asks if it knows the IP address for www.yahoo.com. It actually does, so it returns the IP address to your DNS server, which returns it to the browser, which can then contact the server for www.yahoo.com to get a Web page.
- 51. Redundancy One of the keys to making this work is redundancy. There are multiple DNS servers at every level, so that if one fails, there are others to handle the requests. The other key is caching. Once a DNS server resolves a request, it caches the IP address it receives.
- 52. Redundancy Once it has made a request to a root DNS server for any .COM domain, it knows the IP address for a DNS server handling the .COM domain, so it doesn't have to bug the root DNS servers again for that information. DNS servers can do this for every request, and this caching helps to keep things from bogging down.
- 53. Redundancy Even though it is totally invisible, DNS servers handle billions of requests every day and they are essential to the Internet's smooth functioning. The fact that this distributed database works so well and so invisibly day in and day out is a testimony to the design.
- 57. Web Server Clients that come to a server machine do so with a specific intent, so clients direct their requests to a specific software server running on the server machine. For example, if you are running a Web browser on your machine, it will want to talk to the Web server on the server machine, not the email server.
- 58. Web Server A server has a static IP address that does not change very often. A home machine that is dialing up through a modem, on the other hand, typically has an IP address assigned by the ISP every time you dial in.
- 61. Web Server For example, if a server machine is running a Web server and a file transfer protocol (FTP) server, the Web server would typically be available on port 80, and the FTP server would be available on port 21. Clients connect to a service at a specific IP address and on a specific port number.
- 62. Web Server Once a client has connected to a service on a particular port, it accesses the service using a specific protocol. Protocols are often text and simply describe how the client and server will have their conversation. Every Web server on the Internet conforms to the hypertext transfer protocol (HTTP).
- 63. Web Server Networks, routers, NAPs, ISPs, DNS and powerful servers all make the Internet possible. It is truly amazing when you realize that all this information is sent around the world in a matter of milliseconds!