Subject: [Sipping] ISUP and SIP mapping - 06

From: "Subhodeep Sarkar" <[email-masked]>
Date: Fri, 30 Aug 2002 11:28:43 +0530

Hi,

I have couple of queries regarding the mapping. The first one I suppose
had been 
discussed previously, but I thought of asking once again to clarify the
same.

1. In section 7.2.1, the following statement is bit confusing to me .

" Before sending an IAM the gateway SHOULD connect the backward media 
path (unless provider policy dictates that doing so is unsafe; see
Section 15)."

The message sequences in the draft depicts that the backward media path
is
opened by the PSTN node, immediately after the reception of the IAM.  Is
there
any specific reason for that ? Doesn't it make more sense to open a
backward
media path after receiving of the ACM - which at least concludes that
enough 
info is received to proceed with the call. Otherwise, there is a
possibility that the
media path may carry undesired info (or even a dead air). 

2. Mapping of INVITE and IAM : The tel URI mapping can support more than
simple CDN 
mapping i.e. fax, modem, etc. Why is the same has not been explored in
the draft or 
we can expect some other drafts detailing on the same ? i.e. for example
CGS , CDS can 
be mapped to isdn-subaddress field (isub) to felicitate supplementary
services like DDI, etc. 
Also the USI information can be mapped to different tel URI's like fax
and modem URI to 
pass on more information about the call other than mapping the same
to/from SDP info. 

Cheers,
Subhodeep

Subhodeep Sarkar
Wipro Technologies
*:[email-masked]
*:+91-(0)80-8411990 x1289