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

Hi Robert,
you proposal is similar to idea of Synonymous Labels
<https://tools.ietf.org/html/draft-ietf-mpls-sfl-framework-00>but I'm
afraid it will not scale for SR-MPLS as it require that the whole SR MPLS
stack must consist of such synonymous labels. And that will create state in
the transient nodes in the data plane, IMHO of course.

Regards,
Greg

On Thu, Nov 16, 2017 at 10:26 AM, Robert Raszuk <robert@raszuk.net> wrote:

> The architecture is fine. This is accounting state not forwarding state.
>
> But no new labels are needed.
>
> See on ingress you apply sr label stack based on some match of the fields
> of actual packet. So all you need is to do accounting on the very same
> fields of the packets on egress and you have path accounting required for
> you.
>
> Besides this method also seamlessly works over non sr capable SFs as long
> as such SFs do not mess with the packet content of those tuples.
>
> cheers,
> r.
>
> On Nov 16, 2017 10:05, "Xuxiaohu" <xuxiaohu@huawei.com> 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
>> E：xuxiaohu@huawei.com
>> 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<gregimirsky@gmail.com>;draft-hegde-spring-traffic-acc
>> ounting-for-sr-paths<draft-hegde-spring-traffic-accounting-
>> for-sr-paths@ietf.org>;mpls<mpls@ietf.org>;spring<spring@ietf.org>
>> *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 document https://tools.ietf.org/html/dr
>> aft-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 <spring-bounces@ietf.org> on behalf of Greg Mirsky <
>> gregimirsky@gmail.com>
>> *Date: *Wednesday, November 15, 2017 at 11:10 AM
>> *To: *"draft-hegde-spring-traffic-accounting-for-sr-paths@ietf.org" <
>> draft-hegde-spring-traffic-accounting-for-sr-paths@ietf.org>, "
>> mpls@ietf.org" <mpls@ietf.org>, "spring@ietf.org" <spring@ietf.org>
>> *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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