Bruno - Inline.
From: spring [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, May 12, 2016 8:23 AM To: [email protected] Subject: [spring] draft-ietf-spring-conflict-resolution Hi, As an individual contributor, please find below some comments: -- Isn't this document specific to the MPLS dataplane? If so, it could be indicated in the introduction, and possibly in the abstract. Then this indication could be removed from the 1rst sentence of sections 2 & 3. [Les:] Currently all discussion is regarding SR-MPLS. The draft leaves open the possibility that if there is some SRv6 conflict resolution that needs to be specified it could be added into this document - which is why the Introduction is dataplane agnostic, but each section states specifically that it is relevant to SR-MPLS. I am not aware of any SRv6 conflict resolution that is required at this point, but I prefer to leave the possibility open if that is OK with you. -- §3 "Mapping entries have an explicit context which includes the topology and the SR algorithm." A priori you could add "the routing protocol". [Les:] No - the source of advertisements is deliberately left out. It matters not whether the source of the advertisement is a protocol or an SRMS - nor does it matter which protocol provides the advertisement. You see that "admin distance" is not mentioned at all and that is quite deliberate. This insures that consistent choices are made on nodes regardless of which protocol might have the best route on a given node. -- §3 "When conflicts occur, it is not possible for routers to know which of the conflicting advertisements is "correct". If a router chooses to use one of the conflicting entries forwarding loops and/or blackholes may result unless it can be guaranteed that all other routers in the network make the same choice. Making the same choice requires that all routers have identical sets of advertisements and that they all use the same selection algorithm. » I think we agree on the technical part, but I found the formulation slightly biased. I would propose "When conflicts occur, it is not possible for routers to know which of the conflicting advertisements is "correct". In order to avoid forwarding loops and/or blackholes, there is a need for all nodes to make the same choice. Making the same choice requires that all routers have identical sets of advertisements and that they all use the same selection algorithm. This is the purpose of this document. » -- [Les:] I am fine with this change. §3.1 "Various types of conflicts may occur" What about :s/Various/Two [Les:] "Two" is fine. Just means we will have to change it if we come up with a third type of conflict. :) -- I agree with Robert's and Uma's comment with regards to making this conflict resolution an inter- protocol/routing_table issue. In particular, between SR domains, there is not requirement to have unique SIDs. Hence between PE and CE, between ASes (both within and across organization), the same SID could be reused independently). [Les:] There is more to be said on this topic - co-authors are actively discussing this point and we'll respond more fully to Robert's post in time. But, the draft is NOT trying to define conflict resolution across "SR domains". Perhaps we need language to make that more explicit. > From: Les Ginsberg (ginsberg) [mailto:[email protected]] > Sent: Sunday, May > 01, 2016 7:11 AM > > We are indeed defining conflict resolution across all the SID advertisements > regardless of source (protocol or SRMS) > Why? Because we need consistent use of SIDs in the forwarding plane No: in the forwarding plane, we need a consistent use of MPLS label. [Les:] As you know, SRGB range can be different for different nodes, so the actual label that is used to send a packet for a given destination via Node A may be different than the label used to send the same packet via Node B. It is the SID that needs to be the same - not the label. It is true that SIDs are not installed in the forwarding plane - the labels derived from the SID/SRGB are what is actually installed in the forwarding plane - but I think my use of the word SID in this context is correct. Plus only within an SR domain. Actually, even within a domain, this is dependent on whether SRGB is configured on a per node or a per protocol basis. I'm not sure how much the agreement has been reached on that one. [Les:] The draft currently addresses deployments where a single (set of) SRGB ranges applies to the box. This is by far the most common use case. There is a much more limited use case where protocol specific SRGBs and protocol specific SIDs may be required. The draft will address that in a future revision - but in spirit the same rules will apply - they will just have to take into account "duplicate forwarding domains". Note that this will also require multiple incoming label entries/prefix be supported by the routers in such a network. -- Typo: §2 OLD : Range 3: (500, 5990 NEW : Range 3: (500, 599) (somewhat significant as otherwise range 3 conflict with range 2) [Les:] Agreed - thanx for spotting this. Les Thanks, Regards, Bruno _________________________________________________________________________________________________________________________ Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc pas etre diffuses, exploites ou copies sans autorisation. 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