>> Though, yes, a mixed mode is normally necessary for a while since 'flag' >> days don't exist anymore for >> stuff like IGP and IGPs aren't Apps (yet ;-) ?) that are updated >> over-nite for better or >> for worse. > > good, so you agree we need a way to introduce the new LSAs to network > gradually. Hey Peter, ack obviously > >> understand it would create a loop based on E-TLV information only but >> the old router >> won't have it and throw the packet at you. You would forward using the >> 'new' info. If that is >> not intuitively clear, I can bring some sketches. > > unless there is something in the E-LSA that directly impacts SPF and > path selection, there is no problem. Today, as the new E-LSAs are > defined there is nothing in the encoding that would create the problem > you are referring to. > > As new TLVs are added to the E-LSAs, each time the new TLV is defined > we can mandate to specify which compatibility mode does the new TLV > supports. There can be many TLVs defined, which can happily support > mixed/degraded modes and we should make an effort to let people deploy > these in a incremental fashion.
yes, today there is no problem since the whole thing is just cosmetics. Who cares whether you TLV or fix-packet if semantics are the same. And yes, as long you keep just the 'cosmetics' going, no problem. But then again, what is the stuff really good for. Maybe some excamples of carrying stuff that does not influence SPF and goes into the TLVs would be good (to my mind comes something like label distribution which is not really IGP but useful). So, the moment you add a first semantic changing TLV (basically any information influencing SPF which is basically all the information you're carrying, otherwise it's not IGP, it's generic informating faring around) you will loose all the 'degraded' and so on modes. Simple example: I add to router cap lsa something akin 'overload', i.e. don't use router (I know, it's purely hypothetical and other mechanisms exist). Old routers cannot see that in old style LSA and you cannot make them and there is no 'graceful' migration for this with old routers. You have to run TWO SPFs (basically, multi top) to avoid old routers when forwarding for certain routes or not issue the information (aka, use old style LSAs) until e'one in the area understands E-LSAs. That can span also the whole domain in case of extensions to L2 prefixes. I hope my point got across --- tony
<<attachment: prz.vcf>>
_______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
