Part III Network Layer

1. Part III Network Layer

2. Networking and Internetworking Devices

3. Connecting Devices Following are the networking devices mostly used

4. Connecting Devices and the OSI Model

5. A Repeater in the OSI Model :Repeater is a regenerator not an amplifier

6. A Repeater

7. Function of a Repeater

8. Bridge : Operates in both physical and data link layer

9. A Bridge

10. Function of a Bridge

11. Multiport Bridge

12. Router: Router is Network layer device Router relay packets among multiple interconnected networks

13. Gateway :Is a protocol convertor A gateway accept a packet formatted for one protocol and convert it to packet formatted for another protocol

14. A Gateway

15. Single-Protocol: Designd to route packet belonging to same protocol Multiprotocol Router:Designd to route packet belonging to two or more protocol

16. NETWORK LAYER DUTIES

17. INTERNETWORKING • The Motivation for Internetworking • There are many different LAN and WAN technologies • In real world, computers are connected by many different technologies • Any system that spans a large organization must accommodate multiple technologies • Universal services • Telephones are useful because any telephone can reach any other telephone • Universal service among computers greatly increases the usefulness of each computer • Providing universal service requires interconnecting networks employing different technologies

18. WHAT IS INTERNETWORKING? • A scheme that provides universal service among heterogeneous networks • Hardware • Used to interconnect a set of physical networks • Software • Provide universal services • Internet • System of connected physical networks

19. INTERNETWORK

20. NETWORK LAYER IN AN INTERNETWORK

21. IPv4 ADDRESSES An IPv4 address is a 32-bit address that uniquely and universally defines the connection of a device (for example, a computer or a router) to the Internet. Topics discussed in this section: Address SpaceNotations Classful Addressing Classless Addressing Network Address Translation (NAT)

22. FINDING THE ADDRESS CLASS

23. FINDING THE CLASS IN DECIMAL NOTATION

24. Example 4 Find the class of each address: a. 227.12.14.87 b. 252.5.15.111 c. 134.11.78.56 Solution a. The first byte is 227 (between 224 and 239); the class is D. b. The first byte is 252 (between 240 and 255); the class is E. c. The first byte is 134 (between 128 and 191); the class is B.

25. NETID AND HOSTID

26. NETWORK ADDRESS

27. Example 5 Given the address 23.56.7.91, find the network address. Solution The class is A. Only the first byte defines the netid. We can find the network address by replacing the hostid bytes (56.7.91) with 0s. Therefore, the network address is 23.0.0.0.

28. Example 6 Given the address 132.6.17.85, find the network address. Solution The class is B. The first 2 bytes defines the netid. We can find the network address by replacing the hostid bytes (17.85) with 0s. Therefore, the network address is 132.6.0.0.

29. Example 7 Given the network address 17.0.0.0, find the class. Solution The class is A because the netid is only 1 byte.

30. A NETWORK WITH TWO LEVELS OF HIERARCHY • IP addresses are designed with two levels of hierarchy.

31. A NETWORK WITH THREE LEVELS OF HIERARCHY

32. ADDRESSES IN A NETWORK WITH AND WITHOUT SUBNETTING

33. SUBNET MASK

34. Dotted-decimal notation and binary notation for an IPv4 address

35. Change the following IPv4 addresses from binary notation to dotted-decimal notation. Solution We replace each group of 8 bits with its equivalent decimal number (see Appendix B) and add dots for separation.

36. Change the following IPv4 addresses from dotted-decimal notation to binary notation. Solution We replace each decimal number with its binary equivalent (see Appendix B).

37. Finding the classes in binary and dotted-decimal notation

38. Find the class of each address. a.00000001 00001011 00001011 11101111 b.11000001 10000011 00011011 11111111 c.14.23.120.8 d.252.5.15.111 Solution a. The first bit is 0. This is a class A address. b. The first 2 bits are 1; the third bit is 0. This is a class C address. c. The first byte is 14; the class is A. d. The first byte is 252; the class is E.

39. Mask Address Default masks for classful addressing

40. shows a block of addresses, in both binary and dotted-decimal notation, granted to a small business that needs 16 addresses. We can see that the restrictions are applied to this block. The addresses are contiguous. The number of addresses is a power of 2 (16 = 24), and the first address is divisible by 16. The first address, when converted to a decimal number, is 3,440,387,360, which when divided by 16 results in 215,024,210.

41. A block of 16 addresses granted to a small organization

42. A block of addresses is granted to a small organization. We know that one of the addresses is 205.16.37.39/28. What is the first address in the block? Solution The binary representation of the given address is 11001101 00010000 00100101 00100111 If we set 32−28 rightmost bits to 0, we get 11001101 00010000 00100101 0010000 or 205.16.37.32. This is actually the block shown in Figure 19.3.

43. Find the last address for the block in the above example Solution The binary representation of the given address is 11001101 00010000 00100101 00100111 If we set 32 − 28 rightmost bits to 1, we get 11001101 00010000 00100101 00101111 or 205.16.37.47 This is actually the block shown in Figure 19.3.

44. b. The last address can be found by ORing the given addresses with the complement of the mask. ORing here is done bit by bit. The result of ORing 2 bits is 0 if both bits are 0s; the result is 1 otherwise. The complement of a number is found by changing each 1 to 0 and each 0 to 1.

45. c. The number of addresses can be found by complementing the mask, interpreting it as a decimal number, and adding 1 to it.

46. Configuration and addresses in a subnetted network

47. Three-level hierarchy in an IPv4 address

48. Network and Host Addresses

49. A Network with Two Levels of Hierarchy

50. A Network with Three Levels of Hierarchy