Subject: [Sip] newbie question on SIP 180 vs. 183 messages

From: "Eric King" <[email-masked]>
Date: Thu, 20 Sep 2001 18:08:05 -0700

I am hoping to get an understanding of what to expect in a SIP-to-ISDN
interworking scenario.  

Specifically, I'm in search of something that will indicate what 18x
message should be generated upon:

a. the receipt of an ISDN ALERT message, and

b. the receipt of ISDN Progress/Call Proceeding message,

immediately after a SETUP message is forwarded to the PSTN as a result
of an INVITE.

Unfortunately, I've only stumbled across text that speaks to SS7
interworking.   What might be expected in an ISDN application?  Is there
a reference that someone could point me to?

Thank you so much!

Eric

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From: Gonzalo Camarillo <[email-masked]>
Date: Fri, 21 Sep 2001 04:31:39 +0300

Hello,

If you know that the phone is ringing (an ALERT Q.931 message, for
instance) you send a 180 Ringing. If you receive a notification
indicating that the call is progressing, but you do not know for sure
whether the user is being alterted or not, you send a 183 Session
Progress message.

Regards,

Gonzalo

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