Re: [OSPF] OSPFv3 Extended LSAs TLV-level "disposition-if-unsupporetd indicator"?
Peter Psenak <ppsenak@cisco.com> Tue, 06 August 2013 18:45 UTC
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Date: Tue, 06 Aug 2013 20:45:09 +0200
From: Peter Psenak <ppsenak@cisco.com>
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To: David Lamparter <equinox@diac24.net>
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Subject: Re: [OSPF] OSPFv3 Extended LSAs TLV-level "disposition-if-unsupporetd indicator"?
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David, 00 - ignoring unrecognized TVLs is a standard thing to do 01 - non-MT routers would ignore all TLVs related to MT-ID other then 0 anyway, there is nothing special you need to do. If the non-MT capable router tries to do anything with TLV which is bound to a non-0 MT, or interpret any data that relates to non-0 MT, its a bug on that router. 10 - you can achieve this by advertising the SADR capability in the RI LSA and do it for any prefix coming from the non-SADR router, no per TLV granularity is required. 11 - looks like a router STUB advertisement BTW, we should set the U-bit on all Extended LSAs and I believe Acee has agreed on that already. thanks, Peter On 8/6/13 15:49 , David Lamparter wrote: > Hi ospf WG, > > > looking at the Extended LSA draft from the various use cases, I believe > it would be advantageous to repurpose the topmost two bits of the TLV > type to indicate what should happen if the TLV is not supported by a > router. I'm thinking of 3-4 possible handlings: > > (these all only apply to parent TLVs or LSAs that specify a route in > some way, e.g. currently Inter/Intra/AS-Ext-Prefix LSAs. Though the > first two make sense in a generic way.) > > 00 - ignore TLV > this can be used for all "hint" TLVs, stuff like maybe communicating > the origin ASN for external routes or whatever you can dream up. > > 01 - ignore parent > on calculating SPF, completely ignore the resulting route. This is > useful for MT-OSPF (if it ever happens), to be used on a MT-ID TLV > with an MT-ID != 0. Basically, non-MT routers can ignore all nonzero > MT topologies this way. > > 10 - strong unreachable > mark the route's destination prefix as unreachable and install a > corresponding blackhole/... route. This is the right thing to do on > SADR routes when they hit a non-SADR router. Even if we have the same > prefix reachable on a non-SADR route with a lower metric, we can't > ensure that it's loop-free for a particular source address. > > 11 - weak unreachable (?) > treat the route as "unreachable", adding it to the SPF result as such, > if there is no shorter path to the same prefix so far. This is > probably the least useful type, I can only come up with something like > "route that requires special encapsulation (tunnel?)" - no idea on the > reality here. > > Note that this is supposed to work in conjunction with other ways of > communicating per-router capabilities, e.g. Router Information LSAs. > A router may well need to take a different action when, on calculating, > it notices that it passed by a router without support for feature XYZ. > Since that applies to routers that *do* implement a particular > extension, the exact behaviour for this needs to be specified in that > extension. > > Comments? > > > -David > _______________________________________________ > OSPF mailing list > OSPF@ietf.org > https://www.ietf.org/mailman/listinfo/ospf > >
- [OSPF] OSPFv3 Extended LSAs TLV-level "dispositio… David Lamparter
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… Acee Lindem
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… David Lamparter
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… Russ White
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… Acee Lindem
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… David Lamparter
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… Acee Lindem
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… Russ White
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… A. Przygienda
- Re: [OSPF] OSPFv3 Extended LSAs TLV-level "dispos… Peter Psenak