Subject: [MMUSIC] Question on Verifying ICE Support

From: Philip Matthews <[email-masked]>
Date: Tue, 10 Apr 2007 10:52:10 -0400

Jonathan:

ICE-15 says:

5.1.  Verifying ICE Support

    The answerer will proceed with the ICE procedures defined in this
    specification if the following are all true:

    o  For each media stream, the default destination for at least one
       component of the media stream appears in a candidate attribute.
       For example, in the case of RTP, the IP address and port in the c
       and m line, respectively, appears in a candidate attribute, or  
the
       value in the rtcp attribute appears in a candidate attribute.

Why the "at least one component"? I don't understand why you do not
require that there to be an a=candidate attribute for each component?
In what non-SBC or similar situations do you expect that one component
might match but not the other?

- Philip

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From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 24 Apr 2007 18:02:41 -0400

Hmm. This is one of these cases where, I vaguely recall there was a 
reason for this, but I cannot remember what it is.

Thinking about it now I would have to agree with you, it certainly seems 
more logical that it should be all of them. Unless I can remember why I 
did it this way, I will change it.

-Jonathan R.

Philip Matthews wrote:

>       and m line, respectively, appears in a candidate attribute, or  the

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
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From: Benny Prijono <[email-masked]>
Date: Wed, 25 Apr 2007 09:50:12 +0100

> did it this way, I will change it.

I disagree. IMO the text is correct as it is (although probably it's 
a bit confusing). This is what I understood from the text:

To verify that ICE should be supported for the session, *either* of 
these conditions must be met:
  o the transport address (the default destination) of each media
    stream must be listed as one of the candidate in that media
    stream, OR
  o if rtcp attribute is present, the RTCP address must be listed as
    one of the candidate for the second component for each media
    stream.

IMO requiring that all components must be listed may not work. An 
SBC may modify the media stream address but it leaves RTCP attribute 
unchanged because it doesn't support it.

>> require that there to be an a=candidate attribute for each component?

If I understood correctly, of course there will be a=candidate for 
each component, or otherwise there will be no component!

  -benny

-- 
Benny Prijono
http://www.pjsip.org

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From: Philip Matthews <[email-masked]>
Date: Wed, 25 Apr 2007 16:25:21 -0400

I think all three of us have the same idea, and it is only a question  
of finding a wording that expresses this idea.
The wording must take into account that the "default destination" for  
a particular component can be indicated either in the m and c lines,  
or in other attributes in the SDP.

- Philip

On 25-Apr-07, at 04:50 , Benny Prijono wrote:

>> Hmm. This is one of these cases where, I vaguely recall there was  
>> a reason for this, but I cannot remember what it is.
>> Thinking about it now I would have to agree with you, it certainly  
>> seems more logical that it should be all of them. Unless I can  
>> remember why I did it this way, I will change it.
>
>
> I disagree. IMO the text is correct as it is (although probably  
> it's a bit confusing). This is what I understood from the text:
>
> SBC may modify the media stream address but it leaves RTCP  
> attribute unchanged because it doesn't support it.
>

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From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 26 Apr 2007 13:37:54 -0400

inline.

Benny Prijono wrote:

> I disagree. IMO the text is correct as it is (although probably it's a 
> bit confusing). This is what I understood from the text:
> 
> IMO requiring that all components must be listed may not work. An SBC 
> may modify the media stream address but it leaves RTCP attribute 
> If I understood correctly, of course there will be a=candidate for each 
> component, or otherwise there will be no component!

Sure - but they may not match, since someone has mucked with the SDP but 
didnt adjust the candidate lines. That is the case we are trying to detect.

Interestingly, with the current wording, if an SBC modifies the m/c-line 
but NOT the a=rtcp line, ICE will in fact proceed. So, the question is, 
is that what we want? I suspect not. So I am leaning towards changing 
this back to say that there must be a candidate line for each default.

-Jonathan R.

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From: Benny Prijono <[email-masked]>
Date: Sat, 28 Apr 2007 09:16:21 +0100

> this back to say that there must be a candidate line for each default.

I think that makes sense, and I agree.

  -benny

-- 
Benny Prijono
http://www.pjsip.org

---

From: Philip Matthews <[email-masked]>
Date: Sun, 29 Apr 2007 22:44:33 -0400

On 28-Apr-07, at 04:16 , Benny Prijono wrote:

>> Interestingly, with the current wording, if an SBC modifies the m/ 
>> c-line but NOT the a=rtcp line, ICE will in fact proceed. So, the  
>> question is, is that what we want? I suspect not. So I am leaning  
>> towards changing this back to say that there must be a candidate  
>> line for each default.
>

This also makes sense to me.
- Philip