Re: [AVT] draft-schierl-avt-rtp-multi-session-transmission-00.txt

Err, no. Things like decoding order number go into an RTP payload  
header, as part of a payload format, not into a header extension.

Colin

On 16 Nov 2008, at 16:46, <Ye-Kui.Wang@nokia.com> wrote:
> Thanks for the clarification, which is important. According to  
> this, it
> appears that if the RTP header extenstion contains Decoder Order  
> Number
> information, then there is no problem, as this information not related
> to anything in the RTP header. A good thing is that this solution is
> really generic!
>
> BR, YK
>
>> -----Original Message-----
>> From: ext Randell Jesup [mailto:rjesup@wgate.com]
>> Sent: 16 November, 2008 17:19
>> To: Wang Ye-Kui (Nokia-NRC/Tampere)
>> Cc: ingemar.s.johansson@ericsson.com; avt@ietf.org
>> Subject: Re: [AVT]
>> draft-schierl-avt-rtp-multi-session-transmission-00.txt
>>
>> <Ye-Kui.Wang@nokia.com> writes:
>>>>>> My question is ..how serious is the identified problem ?.
>>>>>> My gut feeling is that a receiver that implements e.g decoding
>>>>>> of G.718 content will likely update the RTP stack to recognize
>>>>>> header extensions if header extensions are used to carry e.g
>>>>>> the NTP timestamp related to the RTP timetstamp in the RTP  
>>>>>> header.
>>>>
>>>> What if an intermediary deletes the header extension?  (SBC, B2BUA,
>>>> raw message store, etc).
>>>
>>> What are the (good) reasons for an intermediary to delete header
>>> extensions? Isn't so that if there is something an
>> intermediary does not
>>> understand, it'd better not to touch the something?
>>
>> True - but if you modify the main package, passing through the header
>> extension becomes tricky.  For example, a B2BUA may leave the payload
>> alone, but almost always rewrites the RTP header, and may
>> generate it's own
>> (or modify passed-through) RTCP packets.  If the header extension
>> references the header (sequence or timestamps), you could be
>> broken.  Or if
>> the header extension references the SSRC, or data carried in the RTCP
>> stream (like NTP time), you could also be broken, and there's no  
>> way to
>> know if you don't understand (and comply with) the extension.
>>
>> I mention things like this because Asterisk does those
>> actions, I think.
>>
>> -- 
>> Randell Jesup, Worldgate (developers of the Ojo videophone),
>> ex-Amiga OS team
>> rjesup@wgate.com
>> "The fetters imposed on liberty at home have ever been forged
>> out of the weapons
>> provided for defence against real, pretended, or imaginary
>> dangers from abroad."
>> 		- James Madison, 4th US president (1751-1836)
>>
>>
> _______________________________________________
> Audio/Video Transport Working Group
> avt@ietf.org
> https://www.ietf.org/mailman/listinfo/avt

-- 
Colin Perkins
http://csperkins.org/

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