Subject: Re: [MMUSIC] updated ICE spec

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 16 Nov 2004 13:27:56 -0500

inline.

Awais Ali wrote:

>> Lets say I have a local socket S1 listening for UDP packets. I use 
>> STUN and TURN to derive two additional address/port pairs for that 
>> socket. I send them out in an invite. THere is one stun server 
>> listening on S1. My peer in the call will perform connectivity checks 
>> to *all three* address/port pairs, all three of which will be stun 
>> requests against the single server on S1. Now, S1 gets an RTP packet. 
>> Presumably, this is because at least one connectivity check has 
>> succeeded for the peer. However, it has three connectivity checks to 
>> do, all three of which are against the same socket, all three of 
>> whicih, if successful, could result in an RTP packet being received on 
>> that socket. Unfortunately, I cannot tell from the RTP packet alone 
>> *which* of these three checks has succeeded and thus generated an RTP 
>> packet. As a result, there is no way for me to know if I may still get 
>> valid STUn requests which need to be checked in order for connectivity 
>> checks to continue.
>>
> Ok I understand that it is not possible to determine from the RTP packet 
> which connection was used. Why can we not use the Giveup timer to 
> determine when the client has stopped its connectivity checks?. If a 
> maximum Giveup-time is specified, a peer can stop its STUN server, 
> Giveup-time after receiving the first RTP packet.

This was discussed at the IETF meeting last week.

The conclusion was that there remained sufficient compelling reasons to 
avoid the usage of so many sockets. As such, the next revision of the 
draft (which I promised to complete this week) will allow for the 
currently documented 1-1 case, and a 1-many case. In the 1-many case, 
the usage of a timer as you suggest can be used. It will be an 
implementation choice as to which approach is used; both interoperate.

-Jonathan R.

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

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