Hi,

>Hi,
> 
>I have a question about "CANCEL" usage..
>When a caller wants to cancel the call, he sends "CANCEL" request to a
>callee..

CANCEL is used when one wants to cancel a TRANSACTION, so in your case
you would use it to cancel the INVITE if you haven't received a final
response for it.

>Is it possible to convey a "cause" parameter with CANCEL request??
>In some application like a PSTN Gateway , it is helpful to convey the
>reason for canceling..
>According to "draft-ietf-sip-isup-00.txt", REL message may be included
>in the CANCEL message body..
>I hope to find a way to convey a cause using a proper SIP header
>field..
>Can anybody help me??

REL is mapped into a CANCEL if you haven't received the final response
for your INVITE, otherwise you map it into a BYE. Note that you can also
map it into BYE even if you have NOT received the final response yet.

Regards,

Christer Holmberg
Ericsson Finland



> 
> Thank you..
> 
> 
> +------------------------------------------+
>   Jae-Min Ahn
>   Senior Engineer
> 
>   Contela, Inc.
>   9-1 Sunae-dong, Pundang-gu,
>   Sungnam City, Kyunggi-do 463-784, Korea
>   Mobile:    +82-11-9076-6104
>   Tel:         +82-342-601-5830~3 (ext:109)
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> +------------------------------------------+
>
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n:Holmberg;Christer
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org:Ericsson;IP Multimedia / Advanced Signalling Research Laboratory
adr:;;;;;;
version:2.1
email;internet:[EMAIL PROTECTED]
title:System Designer
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