[asterisk-dev] SDP negotation problem

[Salvatore Frandina]

Thank you. Hence Asterisk 1.4.29 has a problem...How can I correct it? For
more detail I have attached the SIP-SDP negotiation.

2010/2/8 Olle E. Johansson <oej at edvina.net>

>
> 8 feb 2010 kl. 02.18 skrev Kevin P. Fleming:
>
> > Salvatore Frandina wrote:
> >
> >> I'm using SIPp program to make a call toward Asterisk PBX. The SIP call
> >> works well with Asterisk 1.6 (1.6.0.x, 1.6.1.x and 1.6.2.x) but not with
> >> Asterisk 1.4.x. After I have analyzed the sip message between SIPp and
> >> Asterisk 1.4.29 I have discovered a discrepancy in SDP message.
> >> The RTP payload type is different: SIPp sends 96 dynamic payload type
> >> for H263-1998 - H264 while Asterisk response 103 dynamic type for
> >> H263-1998 - H264. Why? With the other versions there are not problems.
> >
> > SDP offer/answer does not require that both ends use the same payload
> > type numbers for matching payloads; they can differ and it's perfectly
> > acceptable. This is not an error.
> >
> RFC 3264:
>
> " In the case of RTP, if a particular codec was referenced with a
>   specific payload type number in the offer, that same payload type
>   number SHOULD be used for that codec in the answer.  Even if the same
>   payload type number is used, the answer MUST contain rtpmap
>   attributes to define the payload type mappings for dynamic payload
>   types, and SHOULD contain mappings for static payload types.  The
>   media formats in the "m=" line MUST be listed in order of preference,
>   with the first format listed being preferred.  In this case,
>   preferred means that the offerer SHOULD use the format with the
>   highest preference from the answer.
> "
>
> As a developer, we should tread SHOULD treat SHOULD as a MUST, remember :-)
>
> /O
>
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-- 
_______________________________________
Salvatore Frandina
website: http://frandinas.altervista.org
mail: salvatore.frandina at gmail.com

_______________________________________
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