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Chapter 26 IPv6 Addressing

Chapter 26 IPv6 Addressing. 26.1 Introduction . An IPv6 address is 128 bits or 16 bytes (octet) long as shown in Figure 26.1. The address length in IPv6 is four times of the length address in IPv4. Introduction (cont’). Notation Dotted-Decimal Notation

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Chapter 26 IPv6 Addressing

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  1. Chapter 26IPv6 Addressing

  2. 26.1 Introduction • An IPv6 address is 128 bits or 16 bytes (octet) long as shown in Figure 26.1. The address length in IPv6 is four times of the length address in IPv4.

  3. Introduction (cont’) • Notation • Dotted-Decimal Notation 221.14.65.11.105.45.170.34.12.234.18.0.14.0.115.255 • Colon Hexadecimal Notation • To make address more readable • 128 bits are divided into eight sections, each two bytes in length (4 hexadecimal digits) • Therefore, the address consists of 32 hexadecimal digits • Zero compression

  4. Introduction (cont’) • FDEC:14AB:2311:BBFE:AAAA:BBBB:130.24.24.18 • Mixed representation • CIDR (Classless Inter-Domain Routing) Notation

  5. Address Space • The address space of IPv6 contains 2128 addresses • 340,282,366,920,938,463,374,607,431,768,211,456 • 296 times of the IPv4 address

  6. 26.2 Address Space Allocation The address space of IPv6 is divided into several blocks of varying size and each block is allocated for special purpose

  7. Prefix for IPv6 Address

  8. Address Space Allocation (cont’) Algorithm for finding the allocated blocks

  9. Address Space Allocation (cont’) 0000::/8 • IPv4 compatible address • Part of address that use the prefix (00000000) is used to define some IPv4 compatible address • In CIDR notation, this block can be defined as • Unspecified address • Subblock containing only one single address • This address is used during bootstrap • CIDR notation is ::/128

  10. Address Space Allocation (cont’) • Loopback address • This subblock also consists of one single address • This address is used by a host to test itself • The CIDR notation for this one-address is ::1/128

  11. Address Space Allocation (cont’) • Embedded IPv4 address • During the transition from IPv4 to IPv6, host can use their IPv4 address embedded in IPv6 address • A compatible address is an address of 96 bits of zero followed by 32 bits of IPv4 address • Used when a computer using IPv6 wants to send a message to another computer using IPv6 via IPv4 network • A mapped address comprise 80 bits of zero, followed by 16 bits of one, followed by 32-bit IPv4 address • Used when a computer that has migrated to IPv6 wants to send a packet to a computer still using IPv4

  12. Address Space Allocation (cont’) • Global Unicast Block • Main block used for unicast communication between hosts in the Internet • Unique Local Unicast Block • IPv6 uses two large blocks for private addressing • Unique local unicast block can be privately created and used by a site • The block identifier is 1111 110, the next bit can be 0 or 1 to define how the address is selected (locally or by an authority)

  13. Address Space Allocation (cont’) • Link Local Block • The second block designed for private address • Block identifier is 111111 1010 • The next 54 bits are set to zero • The last 64 bits can be changed to define the interface for each computer

  14. Address Space Allocation (cont’) • Multicast Block • In IPv6, a large block of addresses are assigned for multicasting • Prefix is 1111 1111 • The second field is flag field that defines the group address as either permanent or transient • The third field defines the scope of the group address

  15. 26.3 Global Unicast Address • Used for unicast (one-to-one) communication between two hosts in the Internet • CIDR notation for the block is 2000::/3 • The three leftmost bits are the same for all addresses in this block (001) • The size of this block is 125 bits, which is more than enough for the Internet expansion in the many years to come

  16. Global Unicast Address (cont’) • Three Levels of Hierarchy • Recommended length of different parts in unicast addressing

  17. Global Unicast Address (cont’) • Global routing prefix • Used to route the packet through the Internet to organization site such as ISP • The first three bits is 001, the rest of 45 bits can define up to 245 sites • Subnet identifier • Define a subnet in an organization • Organizations can have up to 216 = 65,535 subnets • Interface identifier • The last 64 bits define the interface identifier • EUI-64 and Ethernet MAC

  18. Global Unicast Address (cont’) • Mapping for EUI-64 Mapping for Ethernet MAC

  19. Example 26.11 Find the interface identifier if the physical address in the EUI is (F5-A9-23-EF-07-14-7A-D2)16 using the format we defined for Ethernet addresses. Solution We only need to change the seventh bit of the first octet from 0 to 1 and change the format to colon hex notation. The result is F7A9:23EF:0714:7AD2.

  20. Example 26.12 Find the interface identifier if the Ethernet physical address is (F5-A9-23-14-7A-D2)16 using the format we defined for Ethernet addresses. Solution We only need to change the seventh bit of the first octet from 0 to 1, insert two octet FFFE16 and change the format to colon hex notation. The result is F7A9:23FF:FE14:7AD2 in colon hex.

  21. Example 26.14 An organization is assigned the block 2000:1456:2474/48. What is the IPv6 address of an interface in the third subnet if the IEEE physical address of the computer is (F5-A9-23-14-7A-D2)16. Solution The interface identifier is F7A9:23FF:FE14:7AD2 (see Example 26.12). If we add this identifier to the global prefix and the subnet identifier, we get:

  22. 26.4 Autoconfiguration • One of the interesting features of IPv6 addressing • DHCP protocol can still be used to allocate an IPv6 address to a host, but a host can also configure itself. • The host first creates link local address for itself • 10-bit link local prefix(1111 1110 10), adding 54 zeros, and adding the 64-bit interface identfier • The host then tests to see if this link local address is unique and not used by other hosts • If the link local address is unique, the host stores this address as its link-local address

  23. Example 26.15 Assume a host with Ethernet address (F5-A9-23-11-9B-E2)16has joined the network. What would be its global unicast address if the global unicast prefix of the organization is 3A21:1216:2165 and the subnet identifier is A245:1232. Solution The host first creates its interface identifier as F7A9:23FF:FE11:9BE2 using the Ethernet address read from its card. The host then creates its link-local address as

  24. Example 26.15 (cont’) Assuming that this address is unique, the host sends a router solicitation message and receives the router advertisement message that announces the combination of global unicast prefix and the subnet identifier as 3A21:1216:2165:A245:1232. The host then appends its interface identifier to this prefix to find and store its global unicast address as:

  25. 26.5 Renumbering • Allow sites to change the service provider • If the site changes the provider, the address prefix needs to be changed • A router to which the site is connected can advertise a new prefix and let the site use the old prefix for a short time before disabling it

  26. Summary IPv6, the latest version of the Internet Protocol, has a 128-bit address space. IPv6 uses hexadecimal colon notation with abbreviation methods available. There are three types of addresses: unicast, anycast, and multicast. The variable-type prefix field defines the address type or purpose. To make addresses more readable, IPv6 specifies colon hexadecimal notation. In this notation, 128 bits are divided into eight sections, each 2 bytes (four hexadecimal digits) in length. To abbreviate an address, the leading zeros of a section can be omitted. Zero compression, can also be applied. IPv6 also allows CIDR notation. In IPv6, a destination address can belong to one of the three categories: unicast, anycast, and multicast. A unicast address defines a single interface. An anycast address defines a group of computers only one copy of a packet is sent to one of the computer in the group. A multicast address also defines a group of computers; each member of the group receives a copy of the packet.

  27. Summary The address space of IPv6 is divided into several blocks of varying size and each block is allocated for a special purpose. Most of the blocks are still unassigned and have been left aside for future use. Some block are used for reserved addressed. The most important block is the one with prefix 001, which is used for global unicast addressing (similar to class A, B, C in IPv4 addressing) Two interesting features of IPv6 addressing are autoconfiguration and numbering. In IPv6, a host can be autoconfigured itself in addition to using DHCP. Renumbering allows a site to change its connectivity to another provider and automatically receive a new prefix.

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