I have reviewed this document (draft-ietf-avtext-sdes-hdr-ext-05) as part of the
Operational directorate's  ongoing effort to review all IETF documents being
processed by the IESG.  These comments were written with the intent of improving
the operational aspects of the IETF drafts. Comments that are not addressed in
last call may be included in AD reviews during the IESG review.  Document editors
and WG chairs should treat these comments just like any other last call comments. 

I am not an expert on the details of RTP thus treat my comments are not really on the technical side of the document. I found the document fine and have no concerns with it.

The IDnits comments can be ignored. They are to be fixed by RFC editor when the
RFC numbers are known.

I have few minor comments:

o Line 180 at the beginning of the paragraph starts “That document also..” Since this is the start of the new paragraph I would recommend setting up the context and explicitly say what “that document” is.

o Line 304 "extension word aligned, thus in total 36 bytes.” seems to assume a word is 32 bits. Due historical reasons to avoid confusion I would explicitly state that a 32 bit alignment is what ‘word aligned’ means.

o Line 458 "shall be applied, i.e. discard items that can be determined to be”
           ^^^^^^ although it is not strictly required but I would use the familiar uppercase format here and probably also use more typical MUST here..

- Jouni