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

["Chengli (IP Technology Research)" <[e-mail]>]

Shraddha,

I agree with your point of counters are needed for per flow fully, if we need to measure per flow in SR. 

For measuring performance, some states are needed, and it is good to not create new forwarding states or control states.  It is the same for both solutions.

But I still think 3 or 4(If the reserved label (0-15) can not be assigned ) labels are too many for label stack since the limit of MSD.

For 2 or 3 labels  solution, the limit will become global segments for identifying path.

Regards
Cheng


-----Original Message-----
From: spring [mailto:[e-mail]] On Behalf Of Shraddha Hegde
Sent: Thursday, November 16, 2017 11:11 AM
To: Robert Raszuk <[e-mail]>; Jeff Tantsura <[e-mail]>
Cc: draft-hegde-spring-traffic-accounting-for-sr-paths <[e-mail]>; spring <[e-mail]>; Greg Mirsky <[e-mail]>; mpls <[e-mail]>; Xuxiaohu <[e-mail]>; Zafar Ali (zali) <[e-mail]>
Subject: Re: [spring] [mpls] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths

Robert,

If we have to get the N:1 mapping then we need to count all the N flows on a transit router.
N is really huge number and it is really not practical to count every flow on a transit router.

There have also been comments about creating state in the network.
The proposed solution in the draft does not create per-path forwarding state and does not create any per-path control state in The network. It's only the counters that are getting created per-path which is most essential for OAM.

Rgds
Shraddha

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Robert Raszuk
Sent: Thursday, November 16, 2017 10:51 AM
To: Jeff Tantsura <[e-mail]>
Cc: Xuxiaohu <[e-mail]>; Greg Mirsky <[e-mail]>; spring <[e-mail]>; mpls <[e-mail]>; Zafar Ali (zali) <[e-mail]>; draft-hegde-spring-traffic-accounting-for-sr-paths <[e-mail]>
Subject: Re: [spring] [mpls] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths

As explained it is not needed to get all information required per path.

Yes you may have N:1 mapping of flows to path so what is the problem ?

thx
r.

On Nov 16, 2017 10:47, "Jeff Tantsura" <[e-mail]> wrote:

> Robert,
>
>
>
> HW counters are rather precious resources, but that’s beside the point.
>
> An architecture is not an immutable object, on contrary, a very import 
> property of a good architecture is flexibility and agility, ability to 
> adapt when business need arises.
>
>
>
> Keeping semantics aside – what’s needed, is a metadata (here encoded 
> as a
> label) that uniquely identifies a path, where FIB lookup would yield 
> an “counter hit”, potentially counter creation if the packet is the 
> first packet in the flow. Value of the label would be hashed in the 
> counter ID that is unique and could be resolved by a management layer 
> into accounting record.
>
>
>
> Cheers,
>
> Jeff
>
>
>
> *From: *spring <[e-mail]> on behalf of Robert Raszuk < 
> [e-mail]>
> *Date: *Thursday, November 16, 2017 at 10:26
> *To: *Xuxiaohu <[e-mail]>
> *Cc: *Greg Mirsky <[e-mail]>, spring <[e-mail]>, 
> mpls <[e-mail]>, "Zafar Ali (zali)" <[e-mail]>, 
> draft-hegde-spring-traffic-accounting-for-sr-paths < 
> [e-mail]>
> *Subject: *Re: [spring] [mpls] Special purpose labels in 
> draft-hegde-spring-traffic-accounting-for-sr-paths
>
>
>
> 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" <[e-mail]> 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：[phone]
> E：[e-mail]
> 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<[e-mail]>;draft-hegde-spring-traffic-
> accounting-for-sr-paths<draft-hegde-spring-traffic-
> [e-mail]>;mpls<[e-mail]>;spring<
> [e-mail]>
>
> *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://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_ht
> ml_&d=DwIFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=NyjLsr7JA
> 7mvpCJa0YmPdVKcmMXJ31bpbBaNqzCNrng&m=D8UZYa9EWpns6URXJvtBqZ5gX2lDpl7l5
> ZTaXTlEJGw&s=xB3z335gatRnndYZzanLmzNqezYOznxweYSwcOKuMMo&e=
> 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
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