Hi, Sasha, Just like Rüdiger stated, “SR OAM Use Case” describes a centralized system that is topology-aware to perform data plane monitoring and measurement (including delay measurement between arbitrary points).
“End-to-end liveness monitoring and measurements”, as you write, is not the correct description. Key elements of “SR OAM Use Case” include the realization of a centralized PM server instead of modifying packets. It also allows for measurements between arbitrary points using arbitrary segment lists, with probes from the server and to the server. It does not concern itself with end-to-end measurements per se. And “SR OAM Use Case” is not intended to be a collection of potential use cases either. Orthogonal to this thread. Thanks, — Carlos Pignataro, [email protected]<mailto:[email protected]> On Nov 16, 2017, at 4:51 AM, Alexander Vainshtein <[email protected]<mailto:[email protected]>> wrote: Ruediger hi! I understand that measurement of actual traffic carried in a SR-TE path via a transit link has not been considered in the SR OAM Use Cases draft. It only dealt with end-to-end liveness monitoring and measurements, and this is clearly stated in the Intro section. But, from my POV, these measurements represent a valid OAM use case nevertheless. Regards, Sasha Office: +972-39266302 Cell: +972-549266302 Email: [email protected]<mailto:[email protected]> From: spring [mailto:[email protected]] On Behalf Of [email protected]<mailto:[email protected]> Sent: Thursday, November 16, 2017 11:19 AM To: Alexander Vainshtein <[email protected]<mailto:[email protected]>> Cc: [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]>; Michael Gorokhovsky <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]> Subject: Re: [spring] [mpls] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths Sasha, the purpose of the SR OAM Use Case is to illustrate how Segment Routing enables new ways to perform OAM tasks. Like delay measurements. What is discussed here are new OAM requirements caused by SR. To me, these are part of an own or a different draft. The scope of the SR OAM Use Case never was intended to cover them. Regards, Ruediger Von: Alexander Vainshtein [mailto:[email protected]] Gesendet: Donnerstag, 16. November 2017 09:12 An: Greg Mirsky <[email protected]<mailto:[email protected]>> Cc: draft-hegde-spring-traffic-accounting-for-sr-paths <[email protected]<mailto:[email protected]>>; spring <[email protected]<mailto:[email protected]>>; Zafar Ali (zali) <[email protected]<mailto:[email protected]>>; mpls <[email protected]<mailto:[email protected]>>; Xuxiaohu <[email protected]<mailto:[email protected]>>; Michael Gorokhovsky <[email protected]<mailto:[email protected]>>;[email protected]<mailto:[email protected]> Betreff: RE: [mpls] [spring] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths Greg, I concur with your position: let’s first of all agree that ability to measure traffic carried by an SR-TE LSP in a specific transit node is a require OAM function for SR. I have looked up the SR OAM Use Cases<https://datatracker.ietf.org/doc/draft-ietf-spring-oam-usecase/?include_text=1> draft, and I did not find any relevant use cases there. The only time measurements are mentioned is a reference to an expired implementation report<https://tools.ietf.org/html/draft-leipnitz-spring-pms-implementation-report-00> draft discussing delay measurements. Since delay measurements are in any case based on synthetic traffic, and are always end-to-end (one-way or two-way), this reference is not relevant, IMHO, for this discussion. I have added the authors of the SR OAM Use Cases draft to tis thread. Regards, Sasha Office: +972-39266302 Cell: +972-549266302 Email: [email protected]<mailto:[email protected]> From: mpls [mailto:[email protected]] On Behalf Of Greg Mirsky Sent: Thursday, November 16, 2017 4:28 AM To: Xuxiaohu <[email protected]<mailto:[email protected]>> Cc: draft-hegde-spring-traffic-accounting-for-sr-paths <[email protected]<mailto:[email protected]>>; spring <[email protected]<mailto:[email protected]>>; Zafar Ali (zali) <[email protected]<mailto:[email protected]>>; mpls <[email protected]<mailto:[email protected]>> Subject: Re: [mpls] [spring] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths Dear All, I cannot imagine that operators will agree to deploy network that lacks critical OAM tools to monitor performance and troubleshoot the network. True, some will brave the challenge and be the early adopters but even they will likely request that the OAM toolbox be sufficient to support their operational needs. I see that this work clearly describes the problem and why ability to quantify the flow behavior at internal nodes is important for efficient network operation. First let's discuss whether the case and requirement towards OAM is real and valid. Then we can continue to discussion of what measurement method to use. Regards, Greg On Thu, Nov 16, 2017 at 10:05 AM, Xuxiaohu <[email protected]<mailto:[email protected]>> wrote: Concur. Although it has some values, it's not cost-efficient from my point of view. Network simplicity should be the first priority object. Hence we would have to make some compromise. Best regards, Xiaohu ________________________________ 徐小虎 Xuxiaohu M：+86-13910161692<tel:+86-13910161692> E：[email protected]<mailto:[email protected]> 产品与解决方案-网络战略与业务发展部 Products & Solutions-Network Strategy & Business Development Dept 发件人： Zafar Ali (zali) 收件人： Greg Mirsky<[email protected]<mailto:[email protected]>>;draft-hegde-spring-traffic-accounting-for-sr-paths<[email protected]<mailto:[email protected]>>;mpls<[email protected]<mailto:[email protected]>>;spring<[email protected]<mailto:[email protected]>> 主题： Re: [mpls] [spring] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths 时间： 2017-11-16 02:24:10 Hi, This draft breaks the SR architecture. I am quoting a snippet from abstract of SR Architecture documenthttps://tools.ietf.org/html/draft-ietf-spring-segment-routing-13, which states: “SR allows to enforce a flow through any topological path while maintaining per-flow state only at the ingress nodes to the SR domain.” In addition to creating states at transit and egress nodes, the procedure also affects the data plane and makes it unscalable. It also makes controller job much harder and error prune. In summary, I find the procedure very complex and unscalable. Thanks Regards … Zafar From: spring <[email protected]<mailto:[email protected]>> on behalf of Greg Mirsky <[email protected]<mailto:[email protected]>> Date: Wednesday, November 15, 2017 at 11:10 AM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>>, "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>>, "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: [spring] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths Hi Shraddha, thank you for very well written and thought through draft. I have these questions I'd like to discuss: ••••• Have you thought of using not one special purpose label for both SR Path Identifier and SR Path Identifier+Source SID cases but request two special purpose labels, one for each case. Then the SR Path Identifier would not have to lose the bit for C flag. ••••• And how you envision to collect the counters along the path? Of course, a Controller may query LSR for all counters or counters for the particular flow (SR Path Identifier+Source SID). But in addition I'd propose to use in-band mechanism, perhaps another special purpose label, to trigger the LSR to send counters of the same flow with the timestamp out-band to the predefined Collector. ••••• And the last, have you considered ability to flush counters per flow. In Scalability Considerations you've stated that counters are maintained as long as collection of statistics is enabled. If that is on the node scope, you may have to turn off/on the collection to flush off some old counters. I think that finer granularity, per flow granularity would be useful for operators. Again, perhaps the flow itself may be used to signal the end of the measurement and trigger release of counters. 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