Subject: RE: [SIP] SUS/RES encapsulation

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 11 Jun 2001 01:33:24 -0400

> -----Original Message-----
> From: Gonzalo Camarillo [mailto:[email-masked]]
> Sent: Tuesday, June 05, 2001 7:07 PM
> To: sip
> Cc: Jon Peterson; [email-masked]
> Subject: [SIP] SUS/RES encapsulation
> 
> 
> Hello,
> 
> I have received some feedback regarding the ISUP SUS/RES sequence. In
> the ISUP-SIP mapping draft it is recommended to send them inside a
> re-INVITE with media on hold.
> 
> While everybody agrees that this should be the recommended behavior,
> some folks would like to be able to send SUS/RES in INFO as well. They
> would do so when they were not interested in putting the media on hold
> (in SIP bridging situations for example).
> 
> How do people feel about outlining this possible behavior in 
> the draft?

I don't like it, for two reasons:

1. Its a bad thing to have too many ways to do the same thing.

2. The whole idea with SIP-T is to continue to use SIP to drive call
control, with the ISUP bodies merely providing additional information that
an ISUP gateway might want. Therefore, whenever possible, ISUP functionality
should be mapped to its SIP equivalent. I may be mistaken, but I thought
that SUS really was an end-to-end hold of media, and therefore, should be
mapped to the equivalent function in SIP - a re-INVITE with 0.0.0.0 SDP. 

The point of SIP-T is *not* to simply tunnel all messages in INFO.

-Jonathan R.
---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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---

From: Gonzalo Camarillo <[email-masked]>
Date: Mon, 11 Jun 2001 15:52:47 +0300

Hello,

Jonathan Rosenberg wrote:
> I may be mistaken, but I thought

SUS is used when an ISDN subscriber unplugs his phone from the socket
and plugs it in another socket in the middle of the call. When the call
is SUSpended, the local exchange of the user unplugging the phone cuts
the media, but the rest of the switches do not do anything.

SUS is also sent by the an analog callee when he hangs up, but for our
purposes it does not matter which one of the scenarios we are dealing
with.

I agree with you that SDP 0.0.0.0 is the proper way to go, and that's
why it was included in the draft in the first place. However, I have
been receiving comments about this proposing a differeent mapping.
That's why I wanted to get the opinion of the mailing list. My personal
opinion was written in the draft already.

The proposal that I have received is that, since in the PSTN all the
switches but the local exchange do not do anything, the SUS message can
be mapped to an INFO message, since it does not affect the state of the
session.

Opinions?

Best regards,

Gonzalo
-- 
Gonzalo Camarillo                    Phone :   +1 212 939 71 71
Columbia University                  Mobile:  +358 40 702 35 35
472 Computer Science Building        Fax   :  +358  9 299 30 52
1214 Amsterdam Ave., Mail Code 0401  http://www.hut.fi/~gonzalo
New York, NY 10027                   
USA                              [email-masked]