[SIPForum-discussion] 183 Session Progress

[Jean-Sébastien Decubber]

Hi,

The 100rel support in INVITE message is present to indicate the support of
the reliable provisional response mechanism. This is not used by the
outbound proxy to make a choice about the answer it will send back.

This choice is made by the remote endpoint. If the remote endpoint is a PSTN
gateway it will certainly use the ITU-T recommendation describing the
SIP-ISUP interworking (the recommendation describes how to translate ACM
message from ISUP. It can be either a 180 ringing or a 183 SP).

I hope it helps,
Regards,
JS

2010/1/20 SIP Babie <sipbabie at gmail.com>

> Hi All,
>
> Please let me know when the provisional response  "183 Session Progress" is
> been sent as a reply of INVITE.
> Does Outbound Proxy looks for some header in INVITE on the basis of which
> it sends "183 Session Progress" provisional response, like 100rel support in
> INVITE.
>
> Regards
> SIP Babie
>
>
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