Re: [mpls] [spring] Whether both E2E and SPME performance measurement for MPLS-SR is needed?

[Alexander Vainshtein <[e-mail]>]

I concur with John.


Thump typed by Sasha Vainshtein

________________________________
From: John E Drake <[e-mail]>
Sent: Friday, November 17, 2017 1:33:30 AM
To: Robert Raszuk
Cc: Alexander Vainshtein; [e-mail]; spring; David Allan I
Subject: RE: [spring] [mpls] Whether both E2E and SPME performance measurement for MPLS-SR is needed?

Robert,

How do R6, R2, and R3 determine w/ which SR segment list a packet is associated?  E.g., the tuples in a packet from either R1 or R5 will be the same.

Yours Irrespectively,

John

From: [e-mail] [mailto:[e-mail]] On Behalf Of Robert Raszuk
Sent: Thursday, November 16, 2017 8:44 AM
To: John E Drake <[e-mail]>
Cc: Alexander Vainshtein <[e-mail]>; [e-mail]; spring <[e-mail]>; David Allan I <[e-mail]>
Subject: Re: [spring] [mpls] Whether both E2E and SPME performance measurement for MPLS-SR is needed?

Hi John,

I think I did but let me restate ...

Imagine we have a network like below:


R1 --- R2 --- R3 --- R4
            |
R5 --- R6


R1 and R5 are ingress of SR-MPLS domain and R4 is an egress. You have two SR-MPLS paths:

P1 - R1-R2-R3-R4
P2 - R5-R6-R2-R3-R4

(I know those are SPTs but this is just for illustration).

So on each ingress we need to map packets to SR paths by some match ... it can be based on the dst IP, src/dst IP, port # etc ... So we record those with respect to each path they take.

Now we also record on R4 the same set of tuples.

So now we have all counters needed without asking R4 to report P1 nor P2 (nor need to carry them in the packets) as based on the tuples count which are used on ingress for mapping we can correlate in offline tool the exact count of traffic per ingress segment chain.

In fact we can also derive per path stats even from transit nodes with exact the same type of offline data correlation.

Does anyone see any issue ? Is going offline so bad that we must add labels and modify all hardware to be able to have comfort of using router's CLI to get this data on the routers itself ?

Thx,
R.









On Thu, Nov 16, 2017 at 1:39 PM, John E Drake <[e-mail]<mailto:[e-mail]>> wrote:
Hi,

Or even just an extended email.

Yours Irrespectively,

John

From: Alexander Vainshtein [mailto:[e-mail]<mailto:[e-mail]>]
Sent: Thursday, November 16, 2017 6:59 AM
To: Robert Raszuk <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>; spring <[e-mail]<mailto:[e-mail]>>; David Allan I <[e-mail]<mailto:[e-mail]>>; John E Drake <[e-mail]<mailto:[e-mail]>>
Subject: RE: [spring] [mpls] Whether both E2E and SPME performance measurement for MPLS-SR is needed?

Robert,
Do you plan to post a draft that explains how this can be achieved without changing anything on the wire?
Without such a draft it is a bit difficult to compare the solutions:-)

Regards,
Sasha

Office: [phone]<tel:+972%203-926-6302>
Cell:      [phone]<tel:+972%2054-926-6302>
Email:   [e-mail]<mailto:[e-mail]>

From: spring [mailto:[e-mail]] On Behalf Of Robert Raszuk
Sent: Thursday, November 16, 2017 1:53 PM
To: John E Drake <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>; spring <[e-mail]<mailto:[e-mail]>>; David Allan I <[e-mail]<mailto:[e-mail]>>
Subject: Re: [spring] [mpls] Whether both E2E and SPME performance measurement for MPLS-SR is needed?

Hi John,

If so I stand by my msgs stating that you can accomplish your goal without putting anything new on the wire.

Best,
r.

On Nov 16, 2017 19:43, "John E Drake" <[e-mail]<mailto:[e-mail]>> wrote:
Robert,

I think you’re right that ‘SR Path Id’ is the wrong term and that it should be ‘SR Segment List Id’.  We developed this draft in response to requests from our customers that, as described in our draft, have an interface on a node in the interior of an SR network whose utilization is above a given threshold.  In this situation, they need to be able to know which ingress nodes using which SR segment lists are sending traffic to that interface and how much traffic each ingress nodes is sending on each of its SR segment lists.

This will allow the SR segment lists in question to be adjusted in order to steer traffic away from that interface in a controlled manner.

Yours Irrespectively,

John

From: mpls [mailto:[e-mail]<mailto:[e-mail]>] On Behalf Of Robert Raszuk
Sent: Thursday, November 16, 2017 5:53 AM
To: David Allan I <[e-mail]<mailto:[e-mail]>>
Cc: mpls <[e-mail]<mailto:[e-mail]>>; spring <[e-mail]<mailto:[e-mail]>>
Subject: Re: [mpls] Whether both E2E and SPME performance measurement for MPLS-SR is needed?

/* resending and I got suppressed due to exceeding # of recipients */

Dave,

Two main fundamental points:

1.

Is there any assumption that SR-MPLS paths are end to end (ingress to egress) of a given domain ?

SR does not require end to end paths. In fact this is most beauty of SR that you can add one label to forward packets to different node in SPF topology and you make sure that traffic will be natively flowing from there over disjoined path to native path.

How in those deployment cases all of those discussions here even apply ?

2.

To make a construct of a SR PATH you must assume that SR segments are tightly coupled. And this is very bad as by design segments are not coupled to each other and in fact can be chosen dynamically in transit nodes. In those cases there is no concept of SR PATH at all.

Thx,
R.

On Thu, Nov 16, 2017 at 10:56 AM, David Allan I <[e-mail]<mailto:[e-mail]>> wrote:
I’d rephrase this to be a bit more solution agnostic….


1.       Is E2E PM required. (and this can only be achieved with pairwise measurement points).


2.       Are transit measurement points required as well…..

BTW transmit measurement points without e2e measurement points strikes me as bizarre….

The view from here
Dave

From: spring [mailto:[e-mail]<mailto:[e-mail]>] On Behalf Of Mach Chen
Sent: Thursday, November 16, 2017 5:51 PM
To: Greg Mirsky <[e-mail]<mailto:[e-mail]>>; Alexander Vainshtein <[e-mail]<mailto:[e-mail]>>
Cc: draft-hegde-spring-traffic-accounting-for-sr-paths <[e-mail]<mailto:[e-mail]>>; spring <[e-mail]<mailto:[e-mail]>>; mpls <[e-mail]<mailto:[e-mail]>>; Michael Gorokhovsky <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>; Zafar Ali (zali) <[e-mail]<mailto:[e-mail]>>
Subject: [spring] Whether both E2E and SPME performance measurement for MPLS-SR is needed?

Hi all,

I agree with Sasha and Greg here!

I think the first thing we need to agree on the requirements, then discuss the solution will make more sense. I would ask the following questions:


1.       Is only E2E PM needed for MPLS-SR?

2.       Is only SPME PM needed for MPLS-SR?

3.       Are both E2E and SPME PM needed for MPLS-SR?

Best regards,
Mach


From: mpls [mailto:[e-mail]] On Behalf Of Greg Mirsky
Sent: Thursday, November 16, 2017 5:15 PM
To: Alexander Vainshtein
Cc: draft-hegde-spring-traffic-accounting-for-sr-paths; spring; mpls; Michael Gorokhovsky; [e-mail]<mailto:[e-mail]>; Zafar Ali (zali)
Subject: Re: [mpls] [spring] Special purpose labels in draft-hegde-spring-traffic-accounting-for-sr-paths

Hi Sasha,
many thanks.
I'd point to SR OAM Requirements<https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dietf-2Dspring-2Dsr-2Doam-2Drequirement-2D03&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=CRB2tJiQePk0cT-h5LGhEWH-s_xXXup3HzvBSMRj5VE&m=NMHWJAxk35ikFsOqNiswcGOWr8RLMKDjZIVUWOKbHng&s=O9dIUxKQrlwTmypTpQrHJI2ctXc1U5kWcUB1yEsqPsA&e=> (regrettably expired):

   REQ#13:  SR OAM MUST have the ability to measure Packet loss, Packet

            Delay or Delay variation using Active (using synthetic

            probe) and Passive (using data stream) mode.



I think that our discussion indicates that OAM requirements document is useful at least for as long as we're developing OAM toolset. And the document will benefit from clarification to reflect our discussion that PM may be performed both e2e and over SPME.



Regards,

Greg

On Thu, Nov 16, 2017 at 4:11 PM, Alexander Vainshtein <[e-mail]<mailto:[e-mail]>> wrote:
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://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_doc_draft-2Dietf-2Dspring-2Doam-2Dusecase_-3Finclude-5Ftext-3D1&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=CRB2tJiQePk0cT-h5LGhEWH-s_xXXup3HzvBSMRj5VE&m=NMHWJAxk35ikFsOqNiswcGOWr8RLMKDjZIVUWOKbHng&s=ZBzVsWlwT1TW-rc8hRIu2oXOGTGFWyN8oEpwHOiK63Q&e=> 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://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dleipnitz-2Dspring-2Dpms-2Dimplementation-2Dreport-2D00&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=CRB2tJiQePk0cT-h5LGhEWH-s_xXXup3HzvBSMRj5VE&m=NMHWJAxk35ikFsOqNiswcGOWr8RLMKDjZIVUWOKbHng&s=QfQBqcrZK7iG73fzIFm7Pt92DgaVOiHkhujytZ0q_zo&e=> 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: [phone]<tel:+972%203-926-6302>
Cell:      [phone]<tel:+972%2054-926-6302>
Email:   [e-mail]<mailto:[e-mail]>

From: mpls [mailto:[e-mail]<mailto:[e-mail]>] On Behalf Of Greg Mirsky
Sent: Thursday, November 16, 2017 4:28 AM
To: Xuxiaohu <[e-mail]<mailto:[e-mail]>>
Cc: draft-hegde-spring-traffic-accounting-for-sr-paths <[e-mail]<mailto:[e-mail]>>; spring <[e-mail]<mailto:[e-mail]>>; Zafar Ali (zali) <[e-mail]<mailto:[e-mail]>>; mpls <[e-mail]<mailto:[e-mail]>>
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 <[e-mail]<mailto:[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]<tel:[phone]>
E：[e-mail]<mailto:[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]<mailto:[e-mail]>>;draft-hegde-spring-traffic-accounting-for-sr-paths<[e-mail]<mailto:[e-mail]>>;mpls<[e-mail]<mailto:[e-mail]>>;spring<[e-mail]<mailto:[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://tools.ietf.org/html/draft-ietf-spring-segment-routing-13<https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dietf-2Dspring-2Dsegment-2Drouting-2D13&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=CRB2tJiQePk0cT-h5LGhEWH-s_xXXup3HzvBSMRj5VE&m=NMHWJAxk35ikFsOqNiswcGOWr8RLMKDjZIVUWOKbHng&s=xKKBtL1_7pyQ6k9hakXPemUtJJc9c8wKgw2FgwYttIg&e=>, 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]<mailto:[e-mail]>> on behalf of Greg Mirsky <[e-mail]<mailto:[e-mail]>>
Date: Wednesday, November 15, 2017 at 11:10 AM
To: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[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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