Last Call Review of draft-ietf-isis-te-metric-extensions-07
review-ietf-isis-te-metric-extensions-07-opsdir-lc-mani-2016-02-03-00

Hi all:

I have performed an Operations Directorate review of
   draft-ietf-isis-te-metric-extensions-09

  "In certain networks, such as, but not limited to, financial
   information networks (e.g. stock market data providers), network
   performance criteria (e.g. latency) are becoming as critical to data
   path selection as other metrics.

   This document describes extensions to IS-IS Traffic Engineering
   Extensions (RFC5305) such that network performance information can be
   distributed and collected in a scalable fashion.  The information
   distributed using IS-IS TE Metric Extensions can then be used to make
   path selection decisions based on network performance.

   Note that this document only covers the mechanisms with which network
   performance information is distributed.  The mechanisms for measuring
   network performance or acting on that information, once distributed,
   are outside the scope of this document."

Overall, this draft does what its abstract says, i.e. defines sub-TLVs
that can be used in a specified set of IS-IS TLVs.  These sub-TLVs will
be the initial entries in a new IANA Registry, 'IS-IS TE Metric
Extensions'.

I have one issue to raise: the last paragraph of section 2
(introducing the metrics to for each of the new sub-TLVs) says that
the values "MUST be calculated as rolling averages where the averaging
period MUST be a configurable period of time."  This draft does not
say how that interval will be configured.  For proper operation,
surely all participating IS-IS routers will need to use the same
measurement interval?  I suggest that some text explaining this, and
saying how a router's measurement interval can be checked by other
routers, would be useful.

Apart from that issue, the draft is ready to publish.


Cheers, Nevil

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 Nevil Brownlee                          Computer Science Department
 Phone: +64 9 373 7599 x88941             The University of Auckland
 FAX: +64 9 373 7453   Private Bag 92019, Auckland 1142, New Zealand