Subject: [MMUSIC] Adding a new candidate when ICE running

From: "Zingerle, Meinrad" <[email-masked]>
Date: Mon, 13 Aug 2007 13:25:26 +0200

Hi Jonathan,
 
in my understanding,  section 9.1.2.1. and section 9.3.1.4. allow adding
new candidates without restarting ICE. 
 
    9.1.2.1. Existing Media Streams with ICE Running
    If an agent generates an updated offer including media stream that
    was previously established, and for which ICE checks are in the
    Running state, the agent follows the procedures defined here.
    An agent MUST include candidate attributes for all local candidates
    it had signaled previously for that media stream. The properties of
    that candidate as signaled in SDP - the priority, foundation, type
    and related transport address SHOULD remain the same. The IP
    address, port and transport protocol, which fundamentally identify
    that candidate, MUST remain the same (if they change, it would be a
    new candidate). The component ID MUST remain the same. The agent
    MAY include additional candidates it did not offer previously, but
    which it has gathered since the last offer/answer exchange,
including
    peer reflexive candidates.
 
    9.3.1.4. ICE Continuing for Existing Media Stream
    The valid list is not affected by an updated offer/answer exchange
    unless ICE is restarting.
    If an agent is in the Running state for that media stream, the check
    list is updated (the check list is irrelevant if the state is
    completed). To do that, the agent recomputes the check list using
    the procedures described in Section 5.7. If a pair on the new check
    list was also on the previous check list, and its state was Waiting,
    In-Progress, Succeeded or Failed, its state is copied over.
    Otherwise, its state is set to Frozen.
        .....
 
If my understanding is correct, what's the reason behind it? 
Wouldn't it simplify ICE a little bit, if the ICE draft requests
restarting ICE wehn adding a new candidate to an existing media stream
for that ICE hasn't completed yet? At least the answerer would not have
to recompute the check list and in my opinion requesting an ICE restart
when adding a new candidate would make such scenarios more
deterministic.
 
Thanks for your patience and regards,
  Meinrad
_______________________________________________
mmusic mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/mmusic

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 20 Aug 2007 17:48:27 -0400

A restart is a heavy-handed process really. There are cases where an 
agent doesn't want to wait to finish its gathering before sending the 
initial offer, in order to speed things up. And so it sends the initial 
offer and continues gathering and then sends an updated offer, all to 
make things go faster. If ICE needs to restart on the updated offer, any 
time savings are eliminated.

-Jonathan R.

Zingerle, Meinrad wrote:
>     which it has gathered since the last offer/answer exchange, including
> when adding a new candidate would make such scenarios more deterministic.
>  

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com