1. Chapter 2 The Internet Address Architecture

2. Table 2-1. Example IPv4 addresses written in dotted-quad and binary notation Dotted-Quad RepresentationBinary Representation 0.0.0.000000000 00000000 1.2.3.400000001 00000010 00000011 00000100 10.0.0.25500001010 00000000 00000000 11111111 165.195.130.10710100101 11000011 10000010 01101011 255.255.255.25511111111 11111111

3. Expressing IPv6 Addresses Leading zeros of a block need not be written 0:0:0:0:0:0:0:1 -> ::1. IPv4-mapped IPv6 address. 10.0.0.1 -> ::ffff:10.0.0.1 IPv4-compatible IPv6 address ::0102:f001 -> ::1.2.240.1.

4. Table 2-2. Examples of IPv6 addresses and their binary representations Hex NotationBinary Representation 5f05:2000:80ad:5800:58:800:2023:1d 71 0101111100000101 0010000000000000 1000000010101101 0101100000000000 0000000001011000 0000100000000000 0010000000100011 0001110101110001 ::10000000000000000 0000000000000000 0000000000000000 0000000000000000 0000000000000001 ::1.2.240.1 or ::102:f0010000000000000000 0000000000000000 0000000000000000 0000000100000010 1111000000000001

5. http://[2001:0db8:85a3:08d3:1319:8a2e:0370 :7344]:443/ http://[2001:0db8:85a3:08d3:1319:8a2e:0370 :7344]:443/ refers to port number 443 on IPv6 host 2001:0db8:85a3:08d3:1319:8a2e:0370:7344 using the HTTP/TCP/IPv6 protocols.

6. IPv6 addresses 1.Leading zeros must be suppressed (e.g., 2001:0db8::0022 becomes 2001:db8::22). 2.The :: construct must be used to its maximum possible effect (most blocks of contiguous zeros suppressed) and can go beyond the 16-bit blocks. If multiple blocks contain equal-length runs of zeros, the first is replaced with ::. 3.The hexadecimal digits a through f should be represented in lowercase.

7. Examples IPv6 Address Reduction IPv6 AddressSimplified Notation FF01:0000:0000:0000:0000:0000:0000:0001ff01::1 2031:0000:130F:0000:0000:09C0:876A:130B2031:0:130f::9c0:876a:130b 0000:0000:0000:0000:0000:0000:0000:0001::1 FE80:0000:0000:5EFE:0192.0168.0001.0123fe80::5efe:192.168.1.123 FE80: 0000:0000:0000:1585:4868:495F:D521fe80::1585:4868:495f:d521

8. IPv4 addresses: original partitioning

9. The original (“classful”) IPv4 address space partitioning Clas sAddress Range High-Order BitsUse Fraction of TotalNumber of Nets Number of Hosts A0.0.0.0– 127.255.255.255 0Unicast1/212816,777,216 B128.0.0.0– 191.255.255.255 10Unicast1/416,38465,536 C192.0.0.0– 223.255.255.255 110Unicast1/82,097,152256 D224.0.0.0– 239.255.255.255 1110Multicast1/16N/A E240.0.0.0– 255.255.255.255 1111Reserved1/16N/A

10. Class B Address

11. Subnetting

12. IPv4 subnet mask examples in various formats Dotted-Decimal RepresentationShorthand (Prefix Length)Binary Representation 128.0.0.0/110000000 00000000 00000000 00000000 255.0.0.0/811111111 00000000 00000000 00000000 255.192.0.0/1011111111 11000000 00000000 00000000 255.255.0.0/1611111111 11111111 00000000 00000000 255.255.254.0/2311111111 11111111 11111110 00000000 255.255.255.192/2711111111 11111111 11111111 11100000 255.255.255.255/3211111111 11111111

13. IPv6 subnet mask examples in various formats Hex NotationShorthand (Prefix Length)Binary Representation ffff:ffff:ffff:ffff::/641111111111111111 1111111111111111 00000000000000000000000000000000 ff00::/81111111100000000 0000000000000000 0000000000000000 000000000000000000000000000000000000000000000000

14. Subnet ID (using AND)

15. Variable-Length Subnet Masks (VLSM)

16. Broadcast Address

17. Examples of Prefixes

18. Scaling Problems with IPv4 1.By 1994, over half of all class B addresses had already been allocated. It was expected that the class B address space would be exhausted by about 1995. 2.The 32-bit IPv4 address was thought to be inadequate to handle the size of the Internet anticipated by the early 2000s. 3.The number of entries in the global routing table (one per network number), about 65,000 in 1995, was growing. As more and more class A, B, and C routing entries appeared, routing performance suffered.

19. Aggregation

20. Aggregation: Example Aggregation reduces the size of routing tables

21. Multicast Any Source Multicast (ASM) – Member can receive data from any participant Source Specific Multicast (SSM) – Member can receive data only from one specific source – More Secure – Less Control Traffic in the Internet

22. IPv4 Multicast Addresses Class D: 224.0.0.0 – 239.255.255.255 – 28 free bits provides 2^28 addresses 224.0.0.0 - 224.0.0.255: local network control; never forwarded – 224.0.0.1 is for All hosts in the network 224.0.1.0 – 224.0.1.255: Internetwork control; forwarded normally – 224.0.1.1 used for Network Time Protocol

23. A typical small to medium size enterprise network

24. PA vs PI Addresses Provider-aggregatable and provider- independent IPv4 addresses used in a hypothetical multihomed enterprise. Site operators tend to prefer using PI space if it is available. ISPs prefer PA space because it promotes prefix aggregation and reduces routing table size. Scenarios I: S uses PA address space (12.46.129.0/25) from P1’s block – Advertises at C and D to P1 and P2 – P1 can aggregate to 12/8 block – P2 can’t aggregate – P2 will advertise 12.46.129.0/25 – P2 will route most traffic to S (will attract the traffic for Site S due to longest prefix matching) Scenario II: S uses PI address space – More symmetric – Best metric route is naturally chosen