Subject: [MMUSIC] Clarification about ICE Management of Resources

From: Awais Ali <[email-masked]>
Date: Wed, 27 Oct 2004 17:05:33 -0700

I would like to verify if my understanding of the Management of 
Resources section in the ICE draft is correct.

Let us assume device A and device B want to establish an RTP/RTCP 
session. A and B have 3 addresses each, as follows:

AL: local address of A
AS: Stun derived address for A
AT: Turn derived address for A

BL: local address of B
BS: Stun derived address for B
BT: Turn derived address for B

After A completes its connectivity checks, A's connection table for RTP 
will look like this

1. AS     BS   ... ... ... 0.2    GOOD
2. AS     BT   ... ... ... 0.1    GOOD
3. AS     BL   ... ... ... 0.4    BAD
4. AT     BS   ... ... ... 0.2    GOOD
5. AT     BT   ... ... ... 0.1    GOOD
6. AT     BL   ... ... ... 0.4    BAD
7. AL     BS   ... ... ... 0.2    GOOD
8. AL     BT   ... ... ... 0.1    GOOD
9. AL     BL   ... ... ... 0.4    BAD

Lets say A selects Line 7 to send RTP packets, then A will keep the 
other five connections open by sending keep-alive packets on them. 
Similarly there will be 5 RTCP channels. So in total A has to keep-alive 
10 connections.

B will also have a simillar connnection table. If B also selects the BL 
AS line for sending Media packets, then in the above exampe, we will 
have the situation where A is sending from a different port than it is 
receiving on. In this case then A must send keep alive packets from AS 
to keep the NAT binding open, even if it decides not to keep the other 
connections as backup.

Thanks
Ali

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