The Internet

1. The Internet

2. Understand the architecture of today’s Internet and its relation- ship with ISPs. Understand the importance of the TCP/IP protocol suite. Understand the role of IP, UDP, and TCP in the Internet. Understand the difference between the Internet, an intranet, and an extranet. Know how the Internet began. OBJECTIVES

3. Internet History The internet traces its origins to a military network called ARPANET. ARPANET was created in response to an increased need for national security, and the need to connect remote computing resources. After ARPARET, other private network sprang up , and eventually all of these networks were connected. The connection of these networks formed what we call the Internet. Read the handout

4. Internet • Terms • Internet • Packet Switching Network • Modem - Modulator/Demodulator

5. Internet: is the global collection of computers, communication systems, and software. Public telephone system connects all this equipment to form the internet Packet Switched Network: On a packet switched network, the data is closed in electronic packet. Each packet is individually addressed and forwarded across the network. Modem: Modem stands for modulator/demodulator. Modems are used to send data from a computer over the telephone lines. Computers use digital technology, and the telephone system usually uses analog technology

6. Internet and the Web • It is easy to get the Internet and the web confused, but they are not the same thing. • The Internet is the actual physical network. It is made up of wires, cables and satellites. • The web is the multimedia interface to resources available in the internet. Common use of the Internet are: Communication, shopping, searching, entertainment, education

7. How the Internet Works • Internet is the Packet Switched Network • Data sent in packets • Each packet has an IP address • Every computer in the Network has an address called an IP address. • IP- Internet Protocol; • IP defines the rules of sending communication across the network

8. Internet is the Packet Switched Network • Internet is the switched network means data sent over internet is encapsulated in packets • The packets are addressed according to their destination • Internet database keep track of the addresses and allow networking equipment to forward packet to the correct computer. • This analogy to telephone systems.

9. Basic Internet Architecture

10. Peering ISPs at the same level usually do not charge each other for exchanging messages Higher level ISPs charge lower level ones National ISPs charge regional ISPs which in turn charge local ISPs Local ISPs charge individuals and corporate users for access Packet Exchange Charges

11. Done by through ISP’s Point of Presence (POP) A place ISP provides service to its customers Individual users Typically through a dial-up line using the PPP protocol Handled by the ISP’s modem pool Userid and password checked by Remote Access Server (RAS) Once logged in, the user can send packets over the phone line Corporate users Typically access the POP using a T-1, T-3 or ATM OC-3 connections provided by a common carrier Cost = ISP charges + circuit charges Connecting to an ISP

12. Internet today

13. Internet Governance

14. Internet Society ISOC: Is an international, nonprofit organization formed 1992 to provide support for internet standard process. ISOC supports other Internet administrative bodies such as IAB, IETF, IRTF and IANA, which develop internet standards. ISOC also promotes research and other scholarly activities related to the internet IAB - Internet Architecture Board- sets long term strategies IETF - Internet Engineering Task Force-develop actual standards through series of working groups. IESG manages IETF activities IRTF - Internet Research Task Force IANA - Internet Assign Number Authority

15. Internet administration

16. TCP/IP protocol suite IP: handle datagram routing TCP:is responsible for higher level functions such as segmentation, reassembling, and error detection.

17. TCP/IP Protocol Suite • The suite is made up of five layers. • The Internet is only concerned with the top three layers • The TCP/IP protocol suite installed on any computer involves the network layer-IP and related protocols, transport layer (TCP and UDP) and the application layer SMTP and TELNET). • The low layers are the responsibility of the wide area network that forms the physical internet.

18. IP datagram

19. Technical Focus:Inside the Header of an IP Datagram An IP datagram contains several fields. The most important are the source and destination addresses of the datagram (IP addresses). The header also contains fields related to fragmentation. The size of a datagram may be too large for some LAN or WAN protocols. In this case, the datagram is divided into fragments; each fragment carries the same identification number as well as other information to help the receiver assemble the datagram. The header also has two length fields; one defines the length of the header, the other defines the length of the entire packet. One field that can decrease traffic on the Internet holds the number of routers a packet can visit before it is discarded. The header also contains a checksum field to determine the validity of the packet.

20. IP Address

21. Introduction • The identifier used in the IP layer of the TCP/IP protocol suite to identify each device connected to the Internet is called the Internet address or IP address. • An IP address is a 32-bit address that uniquely and universally defines the connection of a host or a router to the Internet. • IP addresses are unique. They are unique in the sense that each address defines one, and only one, connection to the Internet. • Two devices on the Internet can never have the same address.

22. 8-bit 8-bit An IP address is a 32-bit address. 8-bit 8-bit IP- address is normally written as four decimal number separated by dots (called dotted - decimal notation)

23. The address space of IPv4 is232 or 4,294,967,296.

24. CLASSFULADDRESSING Classful addressing includes the following: • Recognizing Classes • Netid and Hostid • Classes and Blocks • Network Addresses • Sufficient Information • Mask

25. IP Address Classes

29. Occupation of the address space

30. Addresses per class

31. Example 7 Find the class of each address: a. 227.12.14.87 b.193.14.56.22 c.14.23.120.8d. 252.5.15.111 e.134.11.78.56 Solutiona. The first byte is 227 (between 224 and 239); the class is D.b. The first byte is 193 (between 192 and 223); the class is C.c. The first byte is 14 (between 0 and 127); the class is A.d. The first byte is 252 (between 240 and 255); the class is E.e. The first byte is 134 (between 128 and 191); the class is B.

32. Netid and hostid

33. Class-A • Class A is divided into 128 blocks with each block having different netid • First block – 0.0.0.0 to 0.255.255.255 (netid 0) • Second block – 1.0.0.0 to 1.255.255.255 (netid 1) • The last block – 127.0.0.0 to 127.255.255.255 (netid 127)

35. 10 6-bits 8-bits Class-B • Class B is divided into 16384 blocks with each block having different netid • First block – 128.0.0.0 to 128.0.255.255 (netid 128.0) • The last block – 191.255.0.0 to 191.255.255.255 (netid 191.255) = 214=16384 Note: for each block of address the first 2 bytes (netid) are the same.

37. 110 5-bits 8-bits 8-bits Class-C • Class C is divided into 2,097,152 blocks with each block having different netid • First block – 192.0.0.0 to 192.0.255.255 (netid 192.0.0) • The last block – 223.255.255.0 to 223.255.255.255 (netid 223.255.255) = 221=2,097,152 Note: for each block of address the first 3 bytes (netid) are the same.

39. The number of addresses in class C is smaller than the needs of most organizations.

40. Class D addresses are used for multicasting; there is only one block in this class.

41. Class E addresses are reserved for future purposes; most of the block is wasted.

42. In classful addressing, the network address (the first address in the block) is the one that is assigned to the organization. The range of addresses can automatically be inferred from the network address.

43. Example 9 Given the network address 17.0.0.0, find the class, the block, and the range of the addresses. SolutionThe class is A because the first byte is between 0 and 127. The block has a netid of 17. The addresses range from 17.0.0.0 to 17.255.255.255.

44. Example 10 Given the network address 132.21.0.0, find the class, the block, and the range of the addresses. Solution The class is B because the first byte is between 128 and 191. The block has a netid of 132.21. The addresses range from 132.21.0.0 to 132.21.255.255.

45. Example 11 Given the network address 220.34.76.0, find the class, the block, and the range of the addresses. SolutionThe class is C because the first byte is between 192 and 223. The block has a netid of 220.34.76. The addresses range from 220.34.76.0 to 220.34.76.255.

46. Mask • Mask is a 32-bit binary number that gives the first address in the block ( the network address) when ANDed with the address in the block. • The operation is applied bit by bit to the address and the mask

47. Masking concept

48. AND operation

49. Default masks

50. The network address is the beginning address of each block. It can be found by applying the default mask to any of the addresses in the block (including itself). It retains the netid of the block and sets the hostid to zero.