Chapter 2Internet Protocol version 6In this chapter we provide the specifications of the IPv6 protocol. It describes all parameters and features associated with this protocol.2.1 Header Format2.2 AddressingAn IPv6 address is 128 bits represented in 8 hexadecimal blocks, separated by ":". Each block carries 16 bits. Ex. 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 ID Interface ID Figure 2.1 IPv6 address format An IPv6 address is divided into three parts: global routing prefix, subnet ID and interface ID (refer to 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 portion and the host portion since the boundary is always the same. In contrast, in IPv4, the subnet size could vary using the Variable Length Subnet Mask (VLSM) technique. The interface ID is created using the Modified EUI-64 Format Interface Identifiers algorithm, which takes the 48-bit long MAC address of the Ethernet card and expands it to the 64 bits needed for the interface ID. This has a downside. An interface will always have the same interface ID regardless of the site it resides in or the prefix it currently uses and thus the node becomes traceable. IPv6 addresses are of three types:1. Unicast: Uniquely identifies a single...... middle of paper......le, to resolve the link layer address via multicast. The multicast address of the requested node has the format ff02::1:ffxx:xxxx. The multicast address on all nodes is recognized by the prefix ff02::1 and is assigned by default to each IPv6 interface. Through this address you can reach all interfaces with a single packet. In case the IPv6 host is a router, the multicast address will be assigned to all routers with the prefix ff02::2. The following table summarizes all the above mentioned addresses with 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-Local unicast address fe80::240:d0ff:fe8d:4546/64 Multicast address of all nodes ff02::1 Multicast of the solicited node (EUI-64) ff02::1:ff8d: 4546 Solicited- Multicast node ff02::1:ff41:dedfTable 2.1 IPv6 addresses assigned to an interface