Last Call Review of draft-ietf-avt-forward-shifted-red-
review-ietf-avt-forward-shifted-red-secdir-lc-atkins-2010-07-15-00

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 defines a simple enhancement to RFC 2198 to support RTP
   sessions with forward-shifted redundant encodings, i.e., redundant
   data sent before the corresponding primary data.  Forward-shifted
   redundancy can be used to conceal losses of a large number of
   consecutive media frames (e.g., consecutive loss of seconds or even
   tens of seconds of media).

The security considerations section is not written in gramatically
correct English.  While this reader was able to decipher the meaning,
I hope that someone with more editorial capabilities can massage the
text into actual correct English sentences.

Beyond the editorial issues, the document does address the single
issue I see, which is the potential denial of service attack where the
sender sends bogus forward-shifted data, potentially claiming large
buffers in the receiver.  Once the security considerations section is
cleaned up it will more clearly state that "outrageous values" should
be ignored.

-derek

-- 
       Derek Atkins                 617-623-3745
       derek at ihtfp.com             www.ihtfp.com
       Computer and Internet Security Consultant