Hello, Recently I discussed default address selection a bit with implementation folks who were unwilling to put (already implemented) default address selection into the OS.
The main reason was that, as currently specified, default address selection seems like something that can't be implemented AS-IS without a big performance degradation. The thing is, it seems like this (IMO relatively complex) iterative comparison algorithm must be run for every outbound packet (one might be able to optimize a bit with connection-oriented protocols). An alternative seems to be to implement some form of (unspecified -- caching is only discussed in the context of dst address selection) optimizations. One example of optimization could be putting the to-be-used source address in the routing table, and refresh it always when rtable or any address of the node changes or changes state (deprecated/preferred, home address etc.), but these might have their own problems. My worry is, is it useful to specify a mechanism for selection default addresses that can't really be used without critical optimizations? ==== A few comments I came across -- the second at least, IMO, requires a clarification. 1. another issue struct me while re-reading: the draft discusses source/destination address selection separately: with S, select D from D_1, D_2, ..., D_n, or with D, select S from S_1, S_2, ..., S_n. If I understood correctly a fairly common case of S_1, S_2, ..., S_n *AND* D_1, D_1, ..., D_n was not elaborated more (a brief mention in section 2?). 2. IMO, I think sections 3.2 and 3.3 may be a bit ambiguous wrt. mapped addresses and scopes. Is it supposed to say that if I have configured '::ffff:10.0.0.1' on an interface (for some reason..), treat it as global (per 3.3), but if I'm communicating via IPv4 (and it was just added to destination address selection as a mapped address ::ffff:10.0.0.1, treat is as site-local (per 3.2))?!? This surely got me confused! -- Pekka Savola "Tell me of difficulties surmounted, Netcore Oy not those you stumble over and fall" Systems. Networks. Security. -- Robert Jordan: A Crown of Swords -------------------------------------------------------------------- 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] --------------------------------------------------------------------
