Hi Stewart,
Indeed, the same idea can apply to both MPLS-SR and MPLS-LDP. For now,
the requirements that I heard are from MPLS-SR.
Best regards,
Mach
*From:*Stewart Bryant [mailto:stewart.bry...@gmail.com]
*Sent:* Friday, November 17, 2017 10:45 AM
*To:* Mach Chen; stephane.litkow...@orange.com; Robert Raszuk;
Alexander Vainshtein
*Cc:* mpls; spring; Clarence Filsfils;
draft-hegde-spring-traffic-accounting-for-sr-paths; Michael
Gorokhovsky; draft-ietf-spring-oam-usec...@ietf.org; Zafar Ali (zali)
*Subject:* Re: [mpls] [spring] Special purpose labels in
draft-hegde-spring-traffic-accounting-for-sr-paths
I would like to ask a fundamental question here.
Do we need transit counters for only MPLS-SR, or do we need it for
MPLS-LDP as well?
If we need it for both, then we need to have this discussion in a
general MPLS context and not in an MPLS-SR specific context.
At least some of the methods described here would work for both.
Also WRT the proposal to do ingress collection, if nodal paths are
used, that only tells us the approximate path, not the hotspot which I
understand to be the original goal.
- Stewart
On 16/11/2017 14:46, Mach Chen wrote:
Hi Stephane,
If you want to do transit measurement, you have to pay some cost.
The difference is how large the cost is, one, two or multiple labels.
For E2E measurement, it could be much easier. A single label
(could be local or global) is inserted immediately follow the last
label of the SR path. Since there is only one label, the path
label could be put into the stack at the beginning, no matter
whether the measurement is enable or not. With this, it will not
affect the entropy.
Best regards,
Mach
*From:*mpls [mailto:mpls-boun...@ietf.org] *On Behalf Of
*stephane.litkow...@orange.com <mailto:stephane.litkow...@orange.com>
*Sent:* Thursday, November 16, 2017 6:49 PM
*To:* Robert Raszuk; Alexander Vainshtein
*Cc:* mpls; spring; Clarence Filsfils;
draft-hegde-spring-traffic-accounting-for-sr-paths; Michael
Gorokhovsky; draft-ietf-spring-oam-usec...@ietf.org
<mailto:draft-ietf-spring-oam-usec...@ietf.org>; Zafar Ali (zali)
*Subject:* Re: [mpls] [spring] Special purpose labels in
draft-hegde-spring-traffic-accounting-for-sr-paths
Hi,
Yes today we do not have any CLI command on any router to get
paths statistics for LDP (I mean Ingress to Egress) as LDP is
based on MP2P LSPs, so a transit node does not have the knowledge
of the source. From an operational point of view, what we do
today is that we collect netflow statistics on core routers, we
project the label stack onto the routing with an external tool to
get the Ingress to Egress LDP traffic including the mapping of the
flows on the links.
Now for RSVP, we do have such statistics as the LSP is P2P and has
states on every node.
Robert mentioned correctly that SR-TE (especially with MPLS
dataplane) has limited TE features (we cannot mimic all what RSVP
does in SRTE without adding too much complexity).
Thus, is it a problem (transit node stats) worth to be solved ? If
yes, where do we accept to put the complexity ? For a stats issue
I would rather prefer to move the complexity to an external tool
that can do correlations or whatever operations rather than
getting it in the forwarding plane…
IMO, that’s a “nice to have” problem to solve getting that we do
not have this for LDP and we know the limitations of SR-TE MPLS.
However, Ingress stats per SRTE LSP are for sure mandatory to get !
The main drawback I see with the proposed solution is that it
mimics what Entropy label does with a solution which is similar
and at the same time cannot replace entropy label as the provided
entropy is far from being sufficient (this is not the goal I know,
but I was looking for potential use case optimizations). So in a
network running entropy label and this mechanism, a router will
need to find the ELI/EL and hash, then find another special label
to build the stats (maybe tomorrow there will be a third one to
look at and a fourth one…). That starts to be a big overhead for
the forwarding plane.
Brgds,
Stephane
*From:*mpls [mailto:mpls-boun...@ietf.org] *On Behalf Of *Robert
Raszuk
*Sent:* Thursday, November 16, 2017 16:23
*To:* Alexander Vainshtein
*Cc:* spring; Clarence Filsfils; mpls; Michael Gorokhovsky;
draft-ietf-spring-oam-usec...@ietf.org
<mailto:draft-ietf-spring-oam-usec...@ietf.org>;
draft-hegde-spring-traffic-accounting-for-sr-paths; Zafar Ali (zali)
*Subject:* Re: [mpls] [spring] Special purpose labels in
draft-hegde-spring-traffic-accounting-for-sr-paths
Folks,
This thread started and the requirements reported clearly stated
that all what we need is the ability to account per path traffic
on egress nodes.
Now out of the sudden I see requirement popping up to be able to
measure per path in transit nodes.
Well you can do it today with SRv6 if your hardware allows or you
can do it with RSVP-TE.
SR-MPLS is replacing LDP and adds ability for limited TE. But
SR-MPLS never intended to become connection oriented protocol nor
architecture.
So I recommend we take a step back here. Or if you like first go
and fix basic MPLS LDP LSPs to allow per end to end path
accounting in transit nodes then come back here to ask for the
same in SR-MPLS. Not the other way around.
Thx
r.
On Nov 16, 2017 16:12, "Alexander Vainshtein"
<alexander.vainsht...@ecitele.com
<mailto:alexander.vainsht...@ecitele.com>> 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://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 <tel:+972%203-926-6302>
Cell: +972-549266302 <tel:+972%2054-926-6302>
Email: alexander.vainsht...@ecitele.com
<mailto:alexander.vainsht...@ecitele.com>
*From:*mpls [mailto:mpls-boun...@ietf.org
<mailto:mpls-boun...@ietf.org>] *On Behalf Of *Greg Mirsky
*Sent:* Thursday, November 16, 2017 4:28 AM
*To:* Xuxiaohu <xuxia...@huawei.com <mailto:xuxia...@huawei.com>>
*Cc:* draft-hegde-spring-traffic-accounting-for-sr-paths
<draft-hegde-spring-traffic-accounting-for-sr-pa...@ietf.org
<mailto:draft-hegde-spring-traffic-accounting-for-sr-pa...@ietf.org>>;
spring <spring@ietf.org <mailto:spring@ietf.org>>; Zafar Ali
(zali) <z...@cisco.com <mailto:z...@cisco.com>>; mpls
<m...@ietf.org <mailto:m...@ietf.org>>
*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 <xuxia...@huawei.com
<mailto:xuxia...@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 <tel:+86-13910161692>
E：xuxia...@huawei.com <mailto:xuxia...@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<gregimir...@gmail.com
<mailto:gregimir...@gmail.com>>;draft-hegde-spring-traffic-accounting-for-sr-paths<draft-hegde-spring-traffic-accounting-for-sr-pa...@ietf.org
<mailto:draft-hegde-spring-traffic-accounting-for-sr-pa...@ietf.org>>;mpls<m...@ietf.org
<mailto:m...@ietf.org>>;spring<spring@ietf.org
<mailto: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/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 <spring-boun...@ietf.org
<mailto:spring-boun...@ietf.org>> on behalf of Greg Mirsky
<gregimir...@gmail.com <mailto:gregimir...@gmail.com>>
*Date: *Wednesday, November 15, 2017 at 11:10 AM
*To:
*"draft-hegde-spring-traffic-accounting-for-sr-pa...@ietf.org
<mailto:draft-hegde-spring-traffic-accounting-for-sr-pa...@ietf.org>"
<draft-hegde-spring-traffic-accounting-for-sr-pa...@ietf.org
<mailto:draft-hegde-spring-traffic-accounting-for-sr-pa...@ietf.org>>,
"m...@ietf.org <mailto:m...@ietf.org>" <m...@ietf.org
<mailto:m...@ietf.org>>, "spring@ietf.org
<mailto:spring@ietf.org>" <spring@ietf.org
<mailto: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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