Re: [mpls] [spring] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths

[Stewart Bryant <[e-mail]>]

Zafar

I don’t think you can assert that fails to comply with the SR arch. There is nothing they are doing that cannot be captured in Netflix/IPFIX and SR needs to work with IPFIX.

Stewart



> On 16 Nov 2017, at 2:23 am, Zafar Ali (zali) <[e-mail]> wrote:
> 
> Hi,
>  
> This draft breaks the SR architecture. I am quoting a snippet from abstract of SR Architecture document https://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 <[e-mail]> on behalf of Greg Mirsky <[e-mail]>
> Date: Wednesday, November 15, 2017 at 11:10 AM
> To: "[e-mail]" <[e-mail]>, "[e-mail]" <[e-mail]>, "[e-mail]" <[e-mail]>
> 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.
> Regards,
> Greg
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