Hi Everyone,
I've been thinking about how we can use MLD to determine if anyone else is defending an address using DAD. The MLD RFC indicates that a node's link-scope multicast addresses except all-nodes link-scope must be joined using MLD. Since the router receives MLD reports from all devices it knows whether a multicast group is active on the subnet (or should that be link(s)?) for which it is the Querier. If there are no listeners for the solicited-node multicast of the tentative address, then no-one may be DAD defending the address(es) associated with this multicast group. Therefore no-one may have one of these addresses. This means that a node which is aware that it is the first to join this group does not have to complete DAD, because there are can be no other devices which have this address configured. The mechanism I propose to do this for a host to send an extension of an MLD query message, specifying the group which the host wishes to join. The Router which holds a list of all the multicast groups sends back a UNKNOWN_GROUP indication in a (modified) MLD report message if the address is unknown. Reception this message may be used to finish DAD early. If the group is currently active at the Router (and the router responds with an ACTIVE_GROUP message), or if the router does not respond within the timeout period, DAD must be completed in accordance with RFC 2462. In all cases (on timeout, or reception of a response from the Router) an MLD Report is sent from the host to join the multicast group. Backoff mechanisms to prevent DoS on the nodes and Router are being considered. Our team will try to have a draft for discussion within a couple of days. Greg Daley Centre for Telecommunications and Information Engineering Monash University -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
