Subject: [OPSAWG] Performance Metrics Directorate Review of draft-tempia-opsawg-p3m

From: Al Morton <[email-masked]>
Date: Mon, 09 Apr 2012 10:11:31 -0400

OPSAWG,

Vinayak Hegde, a member of the Performance Metrics Directorate,

has reviewed the subject draft.

We offer this early review as part of our directorate mission.

http://www.ietf.org/iesg/directorate/performance-metrics.html

regards,

Al

directorate admin

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Comments on draft-tempia-opsawg-p3m

(
http://datatracker.ietf.org/doc/draft-tempia-opsawg-p3m/)

These comments are for the -01 version on this draft.

1. Doesn't reference prior work in IPPM by RFC number (in the

References section). This is important as the approaches for passive

measurement seem to borrow heavily from the concepts of the IPPM

drafts (active measurements)

IPPM Delay

http://tools.ietf.org/html/rfc2679

IPPM Loss

http://tools.ietf.org/html/rfc2680

2. The draft does not take into out-of-order packet arrivals which
is

possible in a real world scenario. Would the counters be updated or

how will they be switched off. Are there any conditions for
timeouts.

If so, they are not explicitly mentioned.

3. Adding more implementation details of how colouring is done will
be

done will help as it one of the main proposals of the draft. It has

not be covered in sufficient detail - only a few sentences mention

that certain DSCP bits be set but elsewhere the draft mentions that

several "colours" can be used in traffic flows.

4. In sections 6.3 monitoring nodes when there is periodic reading
of

counters, it seems that the implicit upper bound on timeout of 5

minutes as counters are read every 5 minutes. Also there are time

synchnoisation issues when multiple intermediate elements are
involved

in measurement.

5. The authors should elaborate on the data collection methods from

various routers since such measurements may be near real-time to

enable reactions from people monitoring the network. Scalability

concerns apply here when multiple monitoring nodes are needed.