> The pedantic answer is no, routers are not necessarily intermediaries > according to my definition of that term. Intermediaries are entities > or sets of entities that a seeker sends *to* and/or receives *from*, > in order to acquire needed info about a target. If those entities are > not on the same link as the sender, yes, you need routers to enable > that sending and/or receiving, but the routers themselves are not the > destination or source of the seeker-intermediary communication (unless > a router coincidentally happens to be the home of either seeker or > intermediary).
But in comparing a router that forwards packets to a well-known unicast/anycast/multicast address (a L3 intermediary?) and a router with a DHCP relay (a L4+ intermediary) there are significant similarities. The main differences seem to be: - a router failure in the first case can be repaired without telling the host application to try a different address, which may or may not be the case when using a L4+ intermediary. - there exists a routing protocol which is an efficient way to get the intermediaries to find the targets. But because of routing transients when the set of targets change the L3 intermediaries will have stale information. Sure, the routing protocol attempts to minimize that time period. This observation leads me to believe (and I welcome discussion on this) that whatever mechanisms is used for discovery, that if we want a high level of availability, there is a need for an application layer failover mechanism. This could be a combination of the discovery returning a list of IP addresses to use, and the ability for the application to redo the discovery. But solely relying on redoing the discovery will have more delay than when there are multiple IP addresses known from the start. Thus I wonder if the architecture here should take into account the need for such a list of addresses to be provided. Erik -------------------------------------------------------------------- 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] --------------------------------------------------------------------
