Security review of
RTP Stream Identifier Source Description (SDES)
draft-ietf-avtext-rid-04

Do not be alarmed.  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.

We begin by quoting from the document:

"Abstract
   This document defines and registers two new RTCP SDES items.  One,
   named RtpStreamId, is used for unique identification of RTP streams.
   The other, RepairedRtpStreamId, can be used to identify which stream
   a redundancy RTP stream is to be used to repair.

Security considerations:
   The actual identifiers used for RtpStreamIds (and therefore
   RepairedRtpStreamIds) are expected to be opaque."

"Opaque" seems to mean "no one cares what it is."  Nonetheless, a
protocol should give some guidance about this.  Taking the value from
a global 64-bit counter, for example, could leak information about the
global state of the machine.  Having a short counter for each session
with a starting value of 0 would probably be OK.  Having a short
counter start at a random value and wraps around would probably be OK.

The "terminology" section could be improved by EAFMA and RUP
(expanding a few more acronyms and removing unused phrases).  MSID and
SSRC are not expanded; "encoded stream" is never used.

Hilarie