On Mon, Nov 11, 2013 at 04:57:58PM +0000, Acee Lindem wrote: > While this is an interesting discussion, I don't believe this level of > complexity is needed or even desirable. Here are the reasons: > > 1. OSPF is an IGP and is under a single administrative domain. Hence, > you have complete control over what features you deploy. > 2. OSPF LSAs are flooded unchanged. This is different than BGP where > routes are re-advertised with attribute changes. One could argue that > there is readvertisement at the ABR. However, this is best handled by > policy on the ABR rather than having the ABR generically propagate > attributes it may or may not understand. > 3. OSPF has been used for TE and GMPLS path computation without any > requirement for these confusing TLV/sub-TLV mechanisms. In the case of > GMPLS, we have added support for many types of optical networks and have > not required mechanisms such as those discussed this E-mail thread.
+1. Additionally: > On 11/11/13 4:45 AM, "A. Przygienda" <[email protected]> wrote: > >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). This is not correct, or rather incomplete. It is sufficient if B has knowledge of A's supported feature set through other means, i.e. Router Information LSA. It is not neccessary to include this information along with every single TLV/E-LSA. > >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. Yes, you need to know which router supports which features. We're already doing that. We still do not have a reasonable use case for per-TLV mandatory/... bits. Actually, your argument works quite well as an argument that we do _not_ need them. As you said, knowing the TLV processing capabilities of each router is not only neccessary, but also _sufficient_. Therefore, it is sufficient if we know these capabilites from the RI LSA. -David _______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
