Subject: [MMUSIC] draft-ietf-mmusic-ice-05: New offer generating algorithm

From: Vavilapalli Srikanth-A19563 <[email-masked]>
Date: Fri, 16 Sep 2005 16:08:20 +0530

Hi

The draft says that: "The next stage of the algorithm is to let the
connectivity checks continue.  If those checks indicate that a pairing
between the two highest priority candidates from both agents has been
validated, each agent sets a timer whose value is randomly set between 0 and
2 seconds.  When the timer fires a new offer is generated that promotes the
candidate from this validating pairing to active.  ..."

Does this mean that if some of the candidate pairings which are not highest
but having more priority than the current active one become VALID, The agent
should not promote them to active one?

For ex: If peer1 has three candidates with priority 1,2 and 3 (1 being
highest priority) and priority 3 candidate is active one. It has paired
these with some remote candidates of priority 4 and 5 (1-4, 2-4, 3-4, 1-5,
2-5, 3-5). If the 2-4 pairing is the only one became VALID due to
connectivity check process, the algorithm would never promote candidate 2 to
the active one as neither the 2-4 is highest candidate pairing nor all the
pairings are not in INVALID state.

Is this the intention of this algorithm (not to generate OFFER as and when a
higher priority candidate is active)?

Regards
Srikanth Vavilapalli

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From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 30 Sep 2005 00:58:48 -0400

I'll try to answer your question below, but I should point out that the 
specific algorithm here is about to change in the pending ICE revision 
(which I am working on at this very moment). What will happen is that 
the endpoints will create an ordered list of the candidate pairs, and 
both sides will try their connectivity checks at a specific rate, moving 
down the list. The first check to succeed results in a re-invite that 
promotes the candidate to the m/c line.

more below:

> should not promote them to active one?

No, it would get promoted. Though again, this is all changing in the 
draft under development.

> pairings are not in INVALID state.

It would.

-Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
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