Subject: [midcom] framework-04 comments

From: "Bob Penfield" <[email-masked]>
Date: Thu, 1 Nov 2001 12:00:52 -0500

Hi all,

I do have some nits on the framework:

1) I think all occurrences of "In-path" should be removed from section 7.

2) Figure 3 is not correct. In order to match the timeline flows it should
be:

                         ___________
                     --->|   SIP   |<-----\
                    /    |  Proxy  |       \
                   |     |_________|       |
                  1|       |^    ^|       4|
                   |       ||    ||        |
                   |8     2||3  7||6       |5
   ______________  |       ||    ||        |   ______________
   |            |<-/      _v|____|v____     \->|            |
   | External   |    Na   |           |   Nc   | SIP Phone  |
   | SIP phone  |>------->| Middlebox |>------>| within     |
   |            |<-------<|___________|<------<| Pvt. domain|
   |____________|    Nb                   Nd   |____________|

The text in the 2nd paragraph of 7.0 needs to be updated to reflect the
above.

3) Just for correctness, the 100Trying message should precede communication
with the middlebox in all the timeline flows (sections 7.1, 7.2 & 7.2).

4) Section 7.2 & 7.3: The real reason that the SIP proxy must communicate
with the NAT middlebox before sending the INVITE on is that it needs to
change the IP address(es) and port(s) in the SDP of the INVITE to those
allocated by the middlebox. If it does not, the called party will send its
RTP media to the wrong address+port.

5) Section 7.2 & 7.3: The timeline explicitly indicates that the SDP is
modified for the 200-OK response to the INVITE, but not for the INVITE
itself going from the proxy to the private phone.

6) Section 7.2 & 7.3: The "Modify SDP" for the BYE request and the 200-OK
response to the BYE (top of page 24, bottom of page 26 and middle of page
27) should be removed. This message will not contain SDP.

cheers,
(-:bob

Robert F. Penfield
Chief Software Architect
Acme Packet, Inc.
130 New Boston Street
Woburn, MA 01801
[email-masked]

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