On Tue, Dec 30, 2008 at 9:20 PM, Dan Jen <[email protected]> wrote: > Hi all, > > On Tue, 2008-12-30 at 17:41 +1100, Robin Whittle wrote: >> I agree. I think these are poor descriptions of the various mapping >> systems - but only Ivip matches A2b's "real time". >> >> A2c matches APT if we assume the Default Mappers constitute a >> "distributed registry". >> >> Dan, can you confirm that A2c covers APT? > > None of the A2s fit APT exactly. Since all the default mapper systems > hold full mapping tables, as a set they don't really constitute a > 'distributed registry'. But, TRs do query their local default mappers > and cache replies, so maybe A2c comes closest to describing APT.
Hi Dan, If I correctly understand APT (please correct me if I get it wrong), the default mappers contain ITR functionality. Packets sent to them are encapsulated and sent towards an ETR. Next, you layer on the TRs which accelerate the process. Packets to be encapsulated go to the TRs first where a fast, small cache of destinations is consulted. When the TRs encounter a packet they don't currently know how to map, they forward it to the default mapper. In addition to encapsulating the forwarded packet, the default mapper installs a map entry in the TR's cache so that it can handle subsequent packets with the same destination on its own. The default mapper keeps track of the caches in the specific TRs that it serves. When a map affecting one of the cached entries changes, the default mapper updates the TR's caches with the new map. Because the mapper is authoritative for the specific TR's entire cache, it gets around the change notification failure problem from http://bill.herrin.us/network/statechange.html . TTLs and other techniques for expiring the cache aren't necessary; the default mapper handles it. Although the TRs and their default mapper are physically separate pieces of equipment and may not be at the same physical location, they are logically one ITR node which doesn't function without both components. If that description is accurate, the heart of the system is the default mappers which exist in every APT network. How do the default mappers get those full maps? Periodically (A2a) with the expectation that the default mapper must determine which remote ETRs are presently successful or continuously (A2b) as they change to match the currently functioning network topology? Regards, Bill Herrin -- William D. Herrin ................ [email protected] [email protected] 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004 _______________________________________________ rrg mailing list [email protected] https://www.irtf.org/mailman/listinfo/rrg
