Last Call Review of draft-ietf-avtext-rtp-duplication-04
review-ietf-avtext-rtp-duplication-04-opsdir-lc-harrington-2014-02-04-00

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

I was not assigned this ops-dir review, but was assigned a secdir review, so I
had already reviewed this document and thought I would comment.

I think this document is Ready for Publication, with one OPS&Mgmt concern.

Section 7 constrains ftp duplication to managed networks, and discusses the
need for knowledge of network capacity, and observing the losses in each stream
separately to fine-tune the duplication process. But there is no recommendation
about what information should be made accessible by midpoints, or how such
information should be made available.

It happens often that the real-time community rejects requests for
standardization of management, because there are many different environments in
which RT transport occurs. I am not recommending that this document try to
standardize a particular management protocol or data model. (Even though I
think such standardization would be a good thing to do.)

Section 7 contrains this spec to managed networks, but section 7 is about
congestion control. I am not sure I understand the proposal to make capacity
and congestion information observable by the endpoint so it can fine-tune the
duplication process. Is this a recommendation to use layer 7 management
protocols, such as snmp or ipfix, or to use layer 4 congestion management
protocols such as ECN/PCN?

I think there should be a discussion of the information model for information
that should be made available by the elements in the managed network, and
possible mechanisms for delivering that information to the endpoint, to support
ftp duplication.

David Harrington

ietfdbh at comcast.net