Subject: [MMUSIC] Comments on draft-ietf-mmusic-media-path-middleboxes-03

From: "Muthu ArulMozhi Perumal (mperumal)" <[email-masked]>
Date: Tue, 29 Mar 2011 18:51:29 +0530

Overall this draft looks to be in a good shape. 
 
I've one major comment. Similar to REC #2 in section 7, it would be
desirable to have a recommendation that the middlebox present on the
media path allow at least a nominal amount of traffic to be exchanged
between endpoints for a small duration of time (say, one RTT) after the
middlebox receives a message from the MIDCOM agent that indicates the
media session being terminated. This will ensure that any transit
signaling packets on the media path exchanged during the session
termination, like RTCP Bye packets, pass through the middle box.
 
A few minor comments:
1) Section 7 (Preliminary Recommendations)
 
"REC #3: It is recommended that failure to complete signaling on the
media path not automatically cause the session establishment to fail
unless explicitly specified by one or more endpoints.  A fallback
scenario where endpoints retry signaling on the media path is
recommended. A scenario where endpoints retry signaling on the media
path is recommended."
 
The use of the word 'fallback' in the above sentence looks awkward,
since it doesn't refer to an to any fallback mechanism when there is a
failure to complete signaling on the media path. Suggest to remove
'fallback'.
 
2) Section 6.1 (Packet Filtering)
 
Replace:
"For SIP [RFC3261] the typically milestone that must be reached is
offer/answer exchange [RFC3264] accompanied by an acknowledgement that
the dialog has been accepted by the UAS (i.e., 200 OK to the INVITE)."
With:
"For SIP [RFC3261] the typical milestone that must be reached is
offer/answer exchange [RFC3264] accompanied by an acknowledgement that
the dialog has been accepted by the UAS (i.e., 200 OK to the INVITE)."
 
3) Section 4.1.2 (Two-Stage Commit)
 
Replace:
"such as Quality of Service signaling that may require resources to
reserved early on in the call establishment process"
With:
"such as Quality of Service signaling that may require resources to be
reserved early on in the call establishment process"
 
4) Section 5  (NAT Traversal)
 
Replace:
" As shown in Figure 1 the MIDCOM agent that is being co- located with"
With:
" As shown in Figure 1 the MIDCOM agent that is being co-located with"
 
Muthu