1. 19.1 Chapter 19 Network Layer: Logical Addressing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 19.2 Internet Architecture The internet consists of many heterogeneous networks. A network of networks The Internet is a special internet which connects all networks based on the TCP/IP protocol. In Internet, internetworking devices called routers(or gateways) provide interconnections among all networks.

3. 19.3 Net 1 Net 2Net 3 R1R2 Internet real structure router physical net host Internet as a universal network host user’s view Virtual, uniform one network

4. 19.4 IP address IP addresses denote the connection(interface) to the Internet. cf> telephone address, ethernet address IP addresses are unique. Each address defines only on connection to the Internet. IP addresses are global(universal). Any host connected to the Internet must use the same IP addressing scheme.

5. 19.5 IP address An IP address is a 32 bits long. It consists of two parts: net-id and host-id. Net idHost id 32 bits Denote a specific physical network In the Internet Denote a connection in a specific physical network

6. 19.6 Net-id and host-id

7. 19.7 Figure 19.1 Dotted-decimal notation and binary notation for an IPv4 address

8. 19.8 Figure 19.2 Finding the classes in binary and dotted-decimal notation

9. 19.9 Table 19.1 Number of blocks and block size in classful IPv4 addressing

10. 19.10 Table 19.2 Default masks for classful addressing

11. 19.11 Network Address

12. 19.12 Sample Network

13. 19.13 Special IP addresses 0 ’ s mean “ this ”, 1 ’ s mean “ all ” Limited broadcast( local net) 2 all 0s all 1s net host 127anything (often 1) This host 1 Host on this net 1 Directed broadcast for net 2 Loopback 3 Notes: 1 Allowed only at system startup(bootstrap) and is never a valid destination address. 2 Never a valid source address. 3 Should never appear on a network. Used in testing.

14. 19.14 Subnetting IP address is designed with two levels of hierarchy: netid and hostid. Sometimes the block of a network address assigned to an organization need to be divided for efficient routing, so that an organization has several subnetworks(subnets). Subnetting provides a mean to have three levels of hierarchy.

15. 19.15 H1 128.10.1.1 H2 128.10.1.2 Network 128.10.1.0 H3 128.10.2.1 H4 128.10.2.2 Network 128.10.2.0 REST OF THE INTERNET all traffic to 128.10.X.X R All packets with 128.10.x.x are coming to this organization from outside.

16. 19.16 Address with subnet-id

17. 19.17 Subnet Mask The subnet mask specifies how many bits in the host-id are assigned for subnet-id.

18. 19.18 Subnet Example Network ID Subnet ID Host ID 16 8 8 11111111 11111111 11111111 00000000 Network ID Subnet ID Host ID 16 10 6 11111111 11111111 11111111 11 000000 0xffffff00 = 255.255.255.0 0xffffffc0 = 255.255.255.192

19. 19.19 IP addressing: CIDR CIDR: Classless InterDomain Routing subnet portion of address of arbitrary length address format: a.b.c.d/x, where x is # bits in subnet portion of address 11001000 00010111 00010000 00000000 subnet part host part 200.23.16.0/23

20. 19.20 CIDR notation In CIDR, an IP address is expressed as: Network address/length Ex) 234.170.168.0/21 –(234.170.168.0, 234.170.175.255) block Dotted decimal32-bit binary equivalent lowest 234.170.168.0 11101010 10101010 10101000 00000000 highest 234.170.175.255 11101010 10101010 10101111 11111111 CIDR mask 11111111 11111111 11111000 00000000

21. 19.21 Ex) 198.32.0.0/16 (198.32.0.0, 198.32.255.255) block lowest 198.32.0.0 11000110 00100000 00000000 00000000 Highest 198.32.255.255 11000110 00100000 11111111 11111111

22. 19.22 An ISP has the address block of 206.0.64.0/18 (64/24s). If a customer requests 800 IP addresses, then the ISP can assign the address block of 206.0.68.0/22 (4 contiguous/24s) to the customer. What is the advantage of using CIDR comparing with the case of assigning one class B address or 4 class C addresses? ISP’s block 11001110.00000000.01000000.00000000 206.0.64.0/18 client’s block 11001110.00000000.01000100.00000000 206.0.68.0/22 Class C(0) 11001110.00000000.01000100.00000000 206.0.68.0/24 Class C(1) 11001110.00000000.01000101.00000000 206.0.69.0/24 Class C(2) 11001110.00000000.01000110.00000000 206.0.70.0/24 Class C(3) 11001110.00000000.01000111.00000000 206.0.71.0/24 Example

23. 19.23 An ISP is granted a block of addresses starting with 190.100.0.0/16 (65,536 addresses). The ISP needs to distribute these addresses to three groups of customers as follows: a. The first group has 64 customers; each needs 256 addresses. b. The second group has 128 customers; each needs 128 addresses. c. The third group has 128 customers; each needs 64 addresses. Design the subblocks and find out how many addresses are still available after these allocations. Example 19.10

24. 19.24 Solution Figure 19.9 shows the situation. Example 19.10 (continued) Group 1 For this group, each customer needs 256 addresses. This means that 8 (log2 256) bits are needed to define each host. The prefix length is then 32 − 8 = 24. The addresses are

25. 19.25 Example 19.10 (continued) Group 2 For this group, each customer needs 128 addresses. This means that 7 (log2 128) bits are needed to define each host. The prefix length is then 32 − 7 = 25. The addresses are

26. 19.26 Example 19.10 (continued) Group 3 For this group, each customer needs 64 addresses. This means that 6 (log 2 64) bits are needed to each host. The prefix length is then 32 − 6 = 26. The addresses are Number of granted addresses to the ISP: 65,536 Number of allocated addresses by the ISP: 40,960 Number of available addresses: 24,576

27. 19.27 Figure 19.9 An example of address allocation and distribution by an ISP

28. 19.28 Private Address The private addresses are not recognized in the global Internet. IP private addresses can only be used in local networks. The blocks of IP private addresses 10.0.0.0 ~ 10.255.255.255 172.16.0.0 ~ 172.31.255.255 192.168.0.0 ~ 192.168.255.255 The local sites with private addresses can be connected to the global Internet through NAT.

29. 19.29 Figure 19.10 A NAT implementation

30. 19.30 Figure 19.11 Addresses in a NAT

31. 19.31 Figure 19.12 NAT address translation

32. 19.32 Table 19.4 Five-column translation table

33. 19.33 An IPv6 address is 128 bits long. Note

34. 19.34 Figure 19.14 IPv6 address in binary and hexadecimal colon notation

35. 19.35 Figure 19.15 Abbreviated IPv6 addresses

36. 19.36 Figure 19.16 Prefixes for provider-based unicast address