On 11/11/2013 01:05 PM, Anton Smirnov wrote: > Hi Tony, > your thoughts, if I understand you correctly, is to propagate some > universally understood handling information in the header of each TLV. > So far in OSPF intention (and to large extent - the practice) was to > verify ability of routers to understand the information in LSAs via > option bits in LLS/RI LSA (and for older features - in option bits in > LSAs and packets). Hey Anton, correct > > BGP, which you gave as an example of protocol with per-TLV handling > information, is p2p protocol with ability to filter and modify > information per-session and per-prefix. nope, there are other types of TLV based IGPs, PNNI & ISIS being some. BGP is aggregating up and that is where the mandatory etc. stuff plays big time. > OSPF, being link-state protocol, should always remember that all > routers in the area share LSDB view. Verifying feature support per-TLV > is not scalable, mechanism of per-router bits works better. I was talking about per router/per TLV. It is as scalable as the scheme today if you assume new TLV=new capability=new bit basically. The only difference is a larger encoding which given today RAM & CPU is peanuts for the big prize of future extensiblity. The 007 TLV is nothing else but an 'infinite-recursive-capabilities-mask' > > So in your "routing on Sundays" example, author of the feature has > a choice of: > - Do not compute "routing on Sundays" until all routers in the scope > support it > - Define "routing on Sundays" computation algorithm to avoid routers > not supporting it > - etc. etc. > This is all possible and doesn't require per-TLV handling bits.
think through it. let's use: A - old router, no new-TLV support B - new routers, new TLV-support new-TLV is mandatory for SPF you have two cases: . A does NOT compute through B, this is achievable only by seeing mandatory bit on a TLV B advertises on e.g. an interface . B does NOT compute through A, this is ONLY possible if you have the TLV-mask of A, otherwise how do you know A does NOT support the TLV (and yes, you can think about a 'capabilities' mask instead of a 007 TLV). so the condition that you have mandatory bit on a TLV AND you have TLV processing capabilities of every router in the area is NECESSARY AND SUFFICIENT in my opinion. --- tony
<<attachment: prz.vcf>>
_______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
