.5), such as Neighbor Solicitation message from the other node. The 'Retrans Timer' tells us how long nodes should wait between consecutive Neighbor Solicitations and how long to wait for DAD to complete. In this example both reachable and retransmit timers are 10000 milliseconds, which is a longish value in the case of a fixed Ethernet connection. The shown Router Advertisement includes two options: the ICMPv6 PIO and the Source Link-Layer Address Option. The PIO option indicates that the prefix length is 64 bits, which is always the case in Ethernet links ([99] Section 4). Furthermore, the PIO tells via the 'L'-flag bit that the information within can be used for on-link determination (see Section 3.4.2) and via the 'A'-flag bit that the information can be used for SLAAC (see Section 3.5.1). In this trace we can see the Router Address' bit set as well (see Section 3.4.3), which in this environment is a Router Advertisement configuration bug: the system is not using MIPv6 and hence there is no need to communicate the full IPv6 address of the sending router in the PIO. Furthermore, the prefix carried in the PIO does not contain the full IPv6 but just the 64-bit prefix. This is a nice example of the policy of 'be liberal in what you receive', as this misconfiguration in Router Advertisement did not cause any issues for nodes connecting to the link. The 'Not site prefix' flag is a ghost from the past - around the year 2000 there was a proposal by Erik Nordmark a now expired document named draft-ietf-ipngwg-site-prefixes-05.txt, to have a bit to indicate if the included prefix should be accepted and preferred, as was described in the expired document. No current standard actually uses this bit. The most interesting content of the PIO is the 64-bit prefix 2001:14b8:138:42 that hosts will use for SLAAC as described in Section 3.5.1. The Valid lifetime' field indicates that the addresses configured from the included prefix can be used for 86400 seconds (one full day). The 'Preferred lifetime' field indicates how long a