Last Call Review of draft-ietf-ccamp-dpm-
review-ietf-ccamp-dpm-secdir-lc-wierenga-2012-08-21-00

Hi,

I have reviewed this document as part of the security directorate's ongoing
effort to review all IETF documents being processed by the IESG.  These
comments were written primarily for the benefit of the security area directors.
 Document editors and WG chairs should treat these comments just like any other
last call comments.

This document describes a set of path delay metrics in GMPLS/MPLS-TE for
troubleshooting the delay between completion of the signalling process and the
data path establishment and is a such comprehensive. I do have however a number
of fundamental and less fundamental questions that may be caused for my lack of
familiarity with the topic at hand, so please indulge….

Generic:

The central goal of the document appears to be to remedy the fact that
applications think that the data path is available whereas it is not. It is to
me completely unclear why:

- the signalling process can not be changed to terminate only upon availability
of a data path or even easier

- verifying the availability of the data path (send roundtrip packet, if
successful ok)

I can see that the metrics that you are defining may be of use in the control
plane, but I fail to see how they may help the application, I find it hard to
believe that any application would make use of these metrics beyond the binary
value of "is data path available". And that is what you cite as the reason for
this draft. So please expand the goal or argue why you need this set of metrics.

Abstract:

This was very hard for me to parse. For starters, "this delay" does't seem to
refer to any delay previously mentioned. In fact it took me a while to
understand  that it is referring to the time lapsed between finishing
signalling and data path becoming available, I suggest rewording to make that
more clear.

Section  3 (overview):

please expand RRFD, RSRD, PRFD, PSFD, PSRD on first use

Section 5.3 (RRFD metric parameters):

What is the unit of T? UTC?

Section 5.6 (RRFD discussion):

It seems to me that the delays that are introduced by the time to propagate the
signal, the delay introduced by the interfaces etc. are well in the various
milliseconds range, doesn't that invalidate any measurements in that range? Or
can you argue that those introduce a fixed delay so that variations are due to
what you are trying to measure.

The same holds for the other metrics

Section 11.2 (median of metric):

It seems to me that the median is of little value if the majority of the values
are undefined, is that why you have tyne failure count? If so, please say so.

Section 12 (Security considerations):

It is unclear to me what the result of an evil MitM manipulating values of the
metrics could do. Can they for example introduce a denial of service by
reporting high delays? Can they prioritise their own traffic by making
competitors for bandwidth think the data path is not there yet?

Hope this helps,

Klaas