TABLE OF CONTENTS Routing is the process of forwarding PDUs between connected network segments (also known as links or subnets). Routing is a primary function of a network layer protocol, whether it is IP version 4 or version 6. IPv6 routers provide the primary means for joining together two or more IPv6 network segments. Network segments are identified by using an IPv6 network prefix and prefix length. Routers pass IPv6 PDUs from one network segment to another. IPv6 routers are attached to two or more IPv6 network segments and enable hosts on those segments to forward IPv6 PDUs. IPv6 PDUs are exchanged and processed on each host by using IPv6 at layer 3 (the Internet Protocol layer).
Datagrams with a source and destination IP address identified in the header are handed to the IP protocol engine/layer. Above the IPv6 layer, transport services on the source host pass data in the form of TCP segments or UDP PDUs down to the IPv6 layer. IPv6 layer services on each sending host examine the destination address of each PDU, compare this address to a locally maintained routing table, and then determine what additional forwarding is required. The IPv6 layer creates IPv6 PDUs with source and destination address information that is used to route the data through the network. The IPv6 layer then passes PDUs down to the link layer, where the PDUs are converted into frames for transmission over network-specific media on a physical network. This process occurs in reverse order...
