Hi, Shraddha: If you punch a hole in the summary, the other area nodes come to know about the mid-point failure.---> Yes, you're right. Once any node knows about the mid-point failure，It can execution local protection by looking up next sid to fix SRv6 Policy reachability.
Thanks Zhibo From: Lsr [mailto:lsr-boun...@ietf.org] On Behalf Of Shraddha Hegde Sent: Thursday, November 25, 2021 12:11 PM To: Aijun Wang <wangai...@tsinghua.org.cn>; 'Tony Li' <tony...@tony.li> Cc: 'Les Ginsberg (ginsberg)' <ginsb...@cisco.com>; 'Gyan Mishra' <hayabusa...@gmail.com>; 'Christian Hopps' <cho...@chopps.org>; 'lsr' <lsr@ietf.org>; 'Acee Lindem (acee)' <a...@cisco.com>; 'Tony Przygienda' <tonysi...@gmail.com> Subject: Re: [Lsr] 【Responses for Comments on PUAM Draft】RE: IETF 112 LSR Meeting Minutes Aijun, There are multiple possible solutions for the SR-Policy mid-point failure scenario 1. Use anycast SID as mid-points for redundancy 2. Mid-point failure local protection by looking up next sid (This is probably the one you pointed out) 3. E2E S-BFD for SR-Policy path liveness detection If you punch a hole in the summary, the other area nodes come to know about the mid-point failure and remove the failed node reachability. It is not clear how that is solving the SR-Policy liveness problem. Rgds Shraddha Juniper Business Use Only From: Aijun Wang <wangai...@tsinghua.org.cn<mailto:wangai...@tsinghua.org.cn>> Sent: Wednesday, November 24, 2021 11:14 AM To: Shraddha Hegde <shrad...@juniper.net<mailto:shrad...@juniper.net>>; 'Tony Li' <tony...@tony.li<mailto:tony...@tony.li>> Cc: 'Les Ginsberg (ginsberg)' <ginsb...@cisco.com<mailto:ginsb...@cisco.com>>; 'Gyan Mishra' <hayabusa...@gmail.com<mailto:hayabusa...@gmail.com>>; 'Christian Hopps' <cho...@chopps.org<mailto:cho...@chopps.org>>; 'lsr' <lsr@ietf.org<mailto:lsr@ietf.org>>; 'Acee Lindem (acee)' <a...@cisco.com<mailto:a...@cisco.com>>; 'Tony Przygienda' <tonysi...@gmail.com<mailto:tonysi...@gmail.com>> Subject: RE: [Lsr] 【Responses for Comments on PUAM Draft】RE: IETF 112 LSR Meeting Minutes [External Email. Be cautious of content] Hi, Shraddha: If the traffic is steered via the SRv6 policy, the intermediate points should also be protected. There are already one draft to propose the solution( please refer to https://datatracker.ietf.org/doc/html/draft-chen-rtgwg-srv6-midpoint-protection-05<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-chen-rtgwg-srv6-midpoint-protection-05__;!!NEt6yMaO-gk!SSAVRO90Q62ieX5DTTgZBW4FKiC_YHXU9biL8pK-jEOUv7jmUHGUaHAt89kXBaSb$>.) In such situation, if the intermediate points located in different areas, how then know the liveness of each other if ABR has the summary address advertised? We will not consider to configure BFD on every intermediate points. Best Regards Aijun Wang China Telecom From: lsr-boun...@ietf.org<mailto:lsr-boun...@ietf.org> <lsr-boun...@ietf.org<mailto:lsr-boun...@ietf.org>> On Behalf Of Shraddha Hegde Sent: Wednesday, November 24, 2021 1:20 PM To: Tony Li <tony...@tony.li<mailto:tony...@tony.li>>; Aijun Wang <wangai...@tsinghua.org.cn<mailto:wangai...@tsinghua.org.cn>> Cc: Les Ginsberg (ginsberg) <ginsb...@cisco.com<mailto:ginsb...@cisco.com>>; Gyan Mishra <hayabusa...@gmail.com<mailto:hayabusa...@gmail.com>>; Christian Hopps <cho...@chopps.org<mailto:cho...@chopps.org>>; lsr <lsr@ietf.org<mailto:lsr@ietf.org>>; Acee Lindem (acee) <a...@cisco.com<mailto:a...@cisco.com>>; Tony Przygienda <tonysi...@gmail.com<mailto:tonysi...@gmail.com>> Subject: Re: [Lsr] 【Responses for Comments on PUAM Draft】RE: IETF 112 LSR Meeting Minutes WG, MPLS egress protection framework RFC 8679 provides a mechanism to locally protect the traffic during PE failures. The concepts can be applied to SRv6 as well. This mechanism is much more efficient and quick because it locally provides fast protection And switchover to the other PE. If you compare this to the mechanisms being discussed in this thread where the failure information is being propagated by the egress PE to ABR and then ABR to the ingress, the failover is going to be much slower. The egress protection technology does not flood any information outside of the domain and hence does not affect the IGP scale. This is a valid alternate solution to solve the problem at hand IMO. I would be interested to see if people have use cases where egress protection can’t be applied. Rgds Shraddha Juniper Business Use Only From: Lsr <lsr-boun...@ietf.org<mailto:lsr-boun...@ietf.org>> On Behalf Of Tony Li Sent: Tuesday, November 23, 2021 10:22 PM To: Aijun Wang <wangai...@tsinghua.org.cn<mailto:wangai...@tsinghua.org.cn>> Cc: Les Ginsberg (ginsberg) <ginsb...@cisco.com<mailto:ginsb...@cisco.com>>; Gyan Mishra <hayabusa...@gmail.com<mailto:hayabusa...@gmail.com>>; Christian Hopps <cho...@chopps.org<mailto:cho...@chopps.org>>; lsr <lsr@ietf.org<mailto:lsr@ietf.org>>; Acee Lindem (acee) <a...@cisco.com<mailto:a...@cisco.com>>; Tony Przygienda <tonysi...@gmail.com<mailto:tonysi...@gmail.com>> Subject: Re: [Lsr] 【Responses for Comments on PUAM Draft】RE: IETF 112 LSR Meeting Minutes [External Email. Be cautious of content] Hi Aijun, I object to adding negative liveness to the LSDB because of the scale and because it adds scale during failures. [WAJ] If we have no such mechanism, operator should either advertise the host routes across areas(which has scale problem), or lose the fast convergences for some overlay services(which defeat the user experiences). Within the real network, there is very rare chance for the massive failure. And even such thing happen accidently, the information about node liveness is countable, is there any router can’t process such information? The received unreachable information does not trigger the SPF calculation. Will they influence intensively the performance of the router? If the scale is equal, then I would prefer to see flooding positive information rather than negative information. Operationally this is key: if there is a failure and positive information doesn’t propagate, then it’s a bug that will be found in due course and the operator can react outside of a failure scenario. Having a scale failure on top of a topology failure is a far more painful scenario. The odds of a mass failure may be low. The fact of the matter is that they still happen. It is our job to ensure that the IGP performs well when it does. Increasing the size of the LSDB always affects performance. It slows flooding. Some nodes may not realize that SPF is not needed. When LSP fragments are rearranged, inferring that SPF is not necessary is non-trivial. Impacting router and network performance is a given. My understanding is that N node failures would result in O(N) bytes added to the LSDB. If someone has a way to compress that information to O(1), I (and Claude Shannon) would be interested. [WAJ] Do you have other determined solutions except the PUB/SUB mechanism that does not exist in current IGP? None of the mechanisms being discussed currently exist. I have no objections to Robert’s BGP propagation ideas if that’s workable. This is simply not the IGP’s job and the IGP is not a dump truck. Tony
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