TABLE OF CONTENTS The ND protocol packets are carried inside ICMPv6 packets. The ND protocol defines five ICMPv6 packet types for its operation. These packet types are Router Solicitation message, Router Advertisement message, Neighbor Solicitation message, Neighbor Advertisement message, and the Redirect message.
A router sends out Router Advertisement (RA) packets periodically. Router Advertisement messages are also sent in response to Router Solicitation messages received from hosts. Each Router Advertisement message may contain prefix information, link configuration and IPv6 protocol parameters. The Router Advertisement messages indicate the presence of a router and the router s willingness to forward packets. As such, Router Advertisement messages contain information about the transmitting router itself. This information allows a host to perform next-hop determination for outgoing packets. Section 5.8 describes next-hop determination. A host relies on Router Advertisement messages to discover router availability and to build a list of discovered routers called the Default Router List. With the Default Router List the host can continue its communication with off-link peers if the host detects a router failure through NUD. When the host detects a router failure, it will prefer as the next-hop any other reachable router in the list over the unreachable router.
A host sends out Router Solicitation (RS) packets to actively query routers for configuration information as well as for information about the routers. Each router is configured with a time interval for sending out successive Router Advertisement messages. These intervals can range from seconds to minutes. A host may...
