Chapter 2Internet Protocol version 6In this chapter, we provide IPv6 protocol specifications. It describes all the parameters and functionalities associated with this protocol.2.1 Header format2.2 AddressingAn IPv6 address is 128 bits represented in 8 hexadecimal blocks, separated by ':'. Each block contains 16 bits. Ex. X:X:X:X:X:X:X:X ; 2001:4408:0000:0000:0000:c123:7820:1111. It is not case sensitive. A block of zeros or leading zeros in the address can be replaced with '::', but only once. Ex. 2001:4408::c123:7820:11111 64 128Global routing prefix Subnet IDInterface IDFigure 2.1 IPv6 address formatAn IPv6 address is divided into three parts: the global routing prefix, the subnet and interface ID (see Figure 2.1). The global routing prefix helps identify the range of addresses assigned to a site. The subnet ID defines a link within a site. The interface ID identifies an IPv6 interface on a subnet and must be unique within that subnet. For all addresses, the interface ID must be exactly 64 bits long. This makes it easier to differentiate between the network part and the host part since the boundary is always the same. On the contrary, in IPv4, the size of the subnet could vary using the VLSM (Variable length subnet mask) technique. The interface ID is created using the modified EUI-64 format interface identification algorithm, which takes the 48-bit MAC address of the Ethernet card and expands it to the necessary 64 bits for the interface ID. This has a disadvantage. An interface will always have the same interface ID, regardless of the site it resides on or the prefix it is currently using and thus the node becomes traceable. IPv6 addresses are of three types: 1. Unicast - it uniquely identifies a single middle of paper...... file, to resolve the link layer address via multicast. The multicast address of the requested node has the form ff02::1:ffxx:xxxx. The multicast address of all nodes is recognized by the prefix ff02::1 and is assigned by default to each IPv6 interface. Thanks to this address, we can reach all interfaces with a single packet. In case the IPv6 host is a router, it is assigned the multicast address of all routers with the prefix ff02::2. The following table summarizes all the addresses mentioned above with an example. Global unicast address (EUI-64) 2001:db8:72ed:1:240:d0ff:fe8d:4546/64Global unicast address 2001:db8:72ed:1:7d2c:2184:c541:dedf/64Link-Unicast address local fe80::240:d0ff:fe8d:4546/64 Multicast address of all nodes ff02::1 Solicited Node Multicast (EUI-64) ff02::1:ff8d:4546 Solicited - Node Multicast ff02::1 :ff41:dedfTable 2.1 IPv6 addresses assigned to an interface