Re: [ippm] [spring] Monitoring metric to detect and locate congestion

Hi Robert,

The Eulerian path algorithm guarantees to visit all the edges of a graph. In the SR context, we can consider the sub-path between two segments an edge.

Haoyu

From: Robert Raszuk <robert@raszuk.net>
Sent: Thursday, February 27, 2020 11:50 AM
To: Haoyu Song <haoyu.song@futurewei.com>
Cc: Ruediger.Geib@telekom.de; ippm-chairs@ietf.org; spring@ietf.org; ippm@ietf.org
Subject: Re: [spring] Monitoring metric to detect and locate congestion

Hi Haoyu,

> which applies Eulerian Path algorithm to find the minimum set of paths with network-wide coverage.

In practice networks use ECMP. ECMP decision may happen at each hop. Your end to end flows get spread over all ECMP paths. So limiting number of probed paths is inaccurate to the fundamental objective of the exercise.

That is infact main challenge with any end to end path probing today ... if you do not cover all possible paths your packets may take between ingress and egress you just do not get full picture of the network.

Thx a lot,
R.

On Thu, Feb 27, 2020 at 8:44 PM Haoyu Song <haoyu.song@futurewei.com<mailto:haoyu.song@futurewei.com>> wrote:
Hi Ruediger,

I like the general idea that using pre-determined paths in SR to collect performance metrics. I think this approach provides some unique benefits compared with the other approaches. It is also coincident with some of related research work I’m doing.
Here are some thoughts I have.

  1.  I think IOAM could be used as the standard approach for such probing packets. It can collect the performance metrics mentioned in the draft and does more.
  2.  An interesting problem raised by the draft but not fully addressed is the method to plan the optimal paths. There is a work called INT-PATH (https://ieeexplore.ieee.org/document/8737529<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fieeexplore.ieee.org%2Fdocument%2F8737529&data=02%7C01%7Chaoyu.song%40futurewei.com%7C06b91304725b43b1d3ea08d7bbbe428b%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637184298148875164&sdata=6wc6xDzbNQ2RQATvTcGvkpaQNEXUu53w39b4oN7Z9qE%3D&reserved=0>) which applies Eulerian Path algorithm to find the minimum set of paths with network-wide coverage. However, the problem here seems different: you need path coverage redundancy. My question is: do we really need the redundancy to achieve the measurement goal? If so, what’s the best planning algorithm should be? In a real and large scale network, we have constraint on where the probing device(s) can be placed, and we usually want to monitoring the entire network, so an efficient algorithm is necessary.

Best regards,
Haoyu

From: ippm <ippm-bounces@ietf.org<mailto:ippm-bounces@ietf.org>> On Behalf Of Ruediger.Geib@telekom.de<mailto:Ruediger.Geib@telekom.de>
Sent: Tuesday, February 25, 2020 11:55 PM
To: ippm-chairs@ietf.org<mailto:ippm-chairs@ietf.org>
Cc: spring@ietf.org<mailto:spring@ietf.org>; ippm@ietf.org<mailto:ippm@ietf.org>
Subject: [ippm] Monitoring metric to detect and locate congestion

Dear IPPM (and SPRING) participants,

I’m solliciting interest in a new network monitoring metric which allows to detect and locate congested interfaces. Important properties are

  *   Same scalability as ICMP ping in the sense one measurement relation required per monitored connection
  *   Adds detection and location of congested interfaces as compared to ICMP ping (otherwise measured metrics are compatible with ICMP ping)
  *   Requires Segment Routing (which means, measurement on forwarding layer, no other interaction with passed routers – in opposite to ICMP ping)
  *   Active measurement (may be deployed using a single sender&receiver or separate sender and receiver, Segment Routing allows for both options)

I’d be happy to present the draft in Vancouver... If there’s community interest. Please read and comment.

You’ll find slides at

https://datatracker.ietf.org/meeting/105/materials/slides-105-ippm-14-draft-geib-ippm-connectivity-monitoring-00<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fmeeting%2F105%2Fmaterials%2Fslides-105-ippm-14-draft-geib-ippm-connectivity-monitoring-00&data=02%7C01%7Chaoyu.song%40futurewei.com%7C06b91304725b43b1d3ea08d7bbbe428b%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637184298148875164&sdata=gKnVZHYdqQYR%2FWVttXd0unu8a%2Fc3bvcdIXWbQ5TcQtg%3D&reserved=0>

Draft url:

https://datatracker.ietf.org/doc/draft-geib-ippm-connectivity-monitoring/<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-geib-ippm-connectivity-monitoring%2F&data=02%7C01%7Chaoyu.song%40futurewei.com%7C06b91304725b43b1d3ea08d7bbbe428b%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637184298148885111&sdata=Siqk8yVDMNy9fGEPoMJoEr5GpkraxBv4N5hocVDlRL8%3D&reserved=0>

Regards,

Ruediger
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