Re: [OSPF] FW: New Version Notification for draft-ietf-ospf-prefix-link-attr-00.txt
Peter Psenak <ppsenak@cisco.com> Fri, 05 September 2014 08:34 UTC
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Date: Fri, 05 Sep 2014 10:34:04 +0200
From: Peter Psenak <ppsenak@cisco.com>
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To: "A. Przygienda" <prz@zeta2.ch>, ospf@ietf.org
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Archived-At: http://mailarchive.ietf.org/arch/msg/ospf/0g8xm5icxlhG3BeZe5OmV3-b5M0
Subject: Re: [OSPF] FW: New Version Notification for draft-ietf-ospf-prefix-link-attr-00.txt
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Hi Tony, please see inline: On 9/4/14 21:02 , A. Przygienda wrote: > On 09/04/2014 12:24 AM, Peter Psenak wrote: >> Hi Tony, >> >> please see inline: > > Hey Peter, same > >> >> On 9/3/14 18:13 , A. Przygienda wrote: >>> >>> >>> It's also wise to add 'if the same extended prefix TLV (i.e. for same >>> prefix) is seen twice in same opaque LSA only use the first and force >>> people to put all sub-tlvs into a single tlv. >> >> it's kind of obvious, but we can add a text to be sure. > > As I see it, the purpose of an RFC is to assure interoperability. If > there are two > interpretations available of the same packet that will make two > solutions not interoperable, > the standard has to mandate the correct one. ok, we will add a text to make it clear. > >> >>> >>> "OSPFv2 requires functional extension beyond what can readily be done >>> with the fixed-format Link State Advertisements (LSAs) as described >>> in RFC 2328 [OSPFV2]. This document defines OSPF opaque LSAs based >>> on Type-Length-Value (TLV) tuples that can be used to associate >>> additional attributes with advertised prefixes or links." >>> >>> That's strongly suggestive of "you advertise normal LSA and then you use >>> opaque to 'extend' it" . Extended extends and is not independent from >>> original stuff in normal use of English idiom. >> >> because existing LSA are not extensible, any additional link/prefix >> attributes must be advertised in a separate LSAs. We called it >> "extended", but it does not mean that existence of the extended LSA >> require existence of the base LSA. I had a text in the original SR >> draft around that, we can add it here too. > > yepp, once it spelled out, it's obvious but the first conclusion one > jumps to is that they are inter-dependent otherwise. ok, we will add a text to clarify. > >> >> >>> .,.. >>> the area that do not support opaques, an additional text is needed >>> saying "never compute through routers without opaques using information >>> in opaques that influences reachability or metrics". Actually, it's >>> worse since if a router without opaques forwards through a router >>> advertising opaques influencing metrics (for sake or simplicity), you >>> cannot start using opaques to keep on forwarding. In case that all >>> doesn't parse, I can do a simple looping example. >> >> we are not advertising any metrics in the extended LSAs, so I do not >> see why we would have to deal with that case here. If one day someone >> wants to do that, then it would have to be covered in a separate draft >> and we would deal with it at that time. > > agreed here. you're correct. That would be overspecification in this draft > >> >>> OK, I still don't understand 'WHICH flooding scope', the type-3 vs. >>> type-5 one or the 'opaque flodding scope one'. I think you mean 'all >>> prefixes in the same opaque must have the same OSPF-route-type >>> [0+unevens]' but the text is really hard to parse here. >>> >>> Acee, you mean remove the restriction ? I see how some implementations >>> may benefit from cramming all type-3 into the same opaque but I would >>> also suggest to not restrict this and remove the text. >> >> the restriction can not be removed. All the Extended Prefix TLVs that >> you put in a singe Extended Prefix LSA will only use a flooding scope >> of the Extended LSA itself. > > I still think it's not clear what the original paragraph means. prefixes can have different flooding scope. Today intra-area and inter-area prefixes have area flooding scope and external prefixes have domain wide flooding scope. You can not mix prefixes of different flooding scope in a single Extended Prefix LSA, because Extended Prefix LSA can only have a single flooding scope. > >> >>> yes, and again, I think 'extended' is an ill chosen name maybe if that's >>> the intention of the draft. >>> >>> BTW, what is the plan if all the TLVs blow out the MTU of the opaque ? >> >> you can generate many Extended Prefix or Extended Link LSAs, so there >> is no issue. > > ack > >> >>> I'm missing something ? RFC5250 is not describing how the instance >>> (they call it Opaque ID) is supposed to be generated (it references >>> appendix A referencing section 7 which has nothing in it about this). >>> I'm divining the instance allows to have multiple opaques of the same >>> type which leads to bunch interesting discussions >>> * what happens when the MTU gets blown & TLVs are shifted into >>> next 'fragment' in ISIS speak [with all the restrictions how the TLVs >>> can migrate between fragments, ISIS guys suffered this one [as did PNNI] >>> @ length & will surely lend a helping hand in such a case]. >> >> TLVs can come and go and move from one Extended Opaque LSA to the >> other. Implementation needs to track these changes and deal with them. > > I would let the ISIS guys chime in here. They have tons experience with > TLVs sliding fragments and what kind of implementation/operation pain > that can cause. > >> >> >>> * what happens if the same extended prefix TLV shows up twice in >>> two different opaques of same type ? You use the one that is in lower >>> opaque ID ? >> >> I would call it a bug on the originator side. > > yes, but still, the draft should mandate what the desired behavior is @ > this point in time otherwise some will use the lower ID, some higher and > some none of the above & the implementations will not interop ? ok, we will add a tiebreaker there. thanks, Peter > > --- tony > > _______________________________________________ > OSPF mailing list > OSPF@ietf.org > https://www.ietf.org/mailman/listinfo/ospf > . >
- [OSPF] FW: New Version Notification for draft-iet… Acee Lindem (acee)
- Re: [OSPF] FW: New Version Notification for draft… A. Przygienda
- Re: [OSPF] FW: New Version Notification for draft… Peter Psenak
- Re: [OSPF] FW: New Version Notification for draft… Hannes Gredler
- Re: [OSPF] FW: New Version Notification for draft… Acee Lindem (acee)
- Re: [OSPF] FW: New Version Notification for draft… A. Przygienda
- Re: [OSPF] FW: New Version Notification for draft… A. Przygienda
- Re: [OSPF] FW: New Version Notification for draft… Peter Psenak
- Re: [OSPF] FW: New Version Notification for draft… A. Przygienda
- Re: [OSPF] FW: New Version Notification for draft… Hannes Gredler
- Re: [OSPF] FW: New Version Notification for draft… Peter Psenak
- Re: [OSPF] FW: New Version Notification for draft… Acee Lindem (acee)
- Re: [OSPF] FW: New Version Notification for draft… A. Przygienda
- Re: [OSPF] FW: New Version Notification for draft… Acee Lindem (acee)
- Re: [OSPF] FW: New Version Notification for draft… A. Przygienda