IPv6: The Next Generation Internet Protocol
A practical, hands-on guide to the new version of the Internet Protocol, written for network administrators and managers who will work with IPv6.
TABLE OF CONTENTS IPv6: The Next Generation Internet Protocol
Chapter 19: IPv6 Packet Transmission
19.1 INTRODUCTION
In this chapter we will look at the specifications for the frame format for transmission of IPv6 packets. There is a discussion regarding the method of forming IPv6 link-local addresses on Ethernet networks as well as detailing the content of the Source/Target Link-Layer Address option employed in the Router Solicitation, Router Advertisement, Neighbor Solicitation, and Neighbor Advertisement messages. These occur at a point when those messages are transmitted on an Ethernet. Primarily we deal with the transmission of IPv6 packets over Ethernet, FDDI, Token Ring, ARCnet, and PPP networks. Transmission of packets (and routing information) on an Ethernet network is depicted in Figure 19.1).
19.2 FRAME FORMAT
In terms of an Ethernet, IPv6 packets are sent in standard frames. The Ethernet header is composed of the Destination and Source Ethernet addresses and the Ethernet type code, which must be composed of the value 86DD hexadecimal. The data field contains the IPv6 header, immediately succeeded by the payload, and possibly padding octets to meet the minimum frame size for Ethernet.
Maximum Transmission Unit
The default maximum transmission unit (MTU) size for IPv6 packets on an Ethernet is 1500 octets. This size may be decreased by a Router Advertisement that have an MTU option that designates a smaller MTU, or by manual configuration of each node. If a Router Advertisement is received with an MTU option designating an MTU larger than 1500, or larger than a manually configured value less than...
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