Maybe a summary would help: "DIID": - Nodes need to create a link-local address corresponding to every IID they use on a given link (and perform DAD on it). - Nodes don't need to perform DAD for non link-local address. - Multi-link subnet routers would have to defend link-local addresses across links, which could be considered confusing and nonsensical.
"DAD": - Nodes don't need to create otherwise unnecessary link-local addresses corresponding to the IIDs they use for temporary or public-key-derived addresses. - Nodes need to perform DAD on all their addresses. - No strange consequences for multi-link subnets. As far as implementation complexity goes, it seems to me that "DAD" is far simpler, since the rule is the same for all addresses and you don't need to create extra addresses only used for doing DAD. Regarding efficiency, I think it depends upon whether a node has more prefixes or IIDs. For nodes on a link with lots of prefixes, "DIID" saves a little bandwidth by not having to do as much DAD. For nodes with lots of IIDs, "DAD" saves node resources related to configuring twice as many addresses. Offhand, I'd be tempted to give the edge to "DIID" here, but since I've seen various creative proposals for using large numbers of IIDs per node, it's not clear. My machines generally have more IIDs then prefixes. But I think the numbers have to get pretty significant in either case before these concerns begin to matter. The multi-link subnet router issue is more clear. "DAD" is a better architectural fit. Link-local addresses stay link-local and don't become these quasi-subnet-local addresses that are unique across the subnet but only reachable on-link. My take: given that it appears the majority of implementations currently do "DAD", and that "DAD" provides for a cleaner multi-link subnet architecture, I think "DAD" is the better choice. --Brian -------------------------------------------------------------------- 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] --------------------------------------------------------------------
