Subject: [SIP] Hold & then re-INVITE without media

From: "Brett Tate" <[email-masked]>
Date: Wed, 21 Jun 2000 22:07:18 -0400

A -- Invite (hold media) --> B
  <-- 200 (hold media) --   B
   --- Ack -------------------->  B

After A requests B to hold, how can A without providing media request 
that B stop holding and provide media?

I just wanted to verify that the following should work unless B 
has also pushed the hold button.

A -- Invite -------------------> B
  <-- 200 (media) ---------   B
   --- Ack (media) -------->  B

---

From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 22 Jun 2000 12:52:35 -0400

> Brett Tate wrote:

I'm having a bit of trouble parsing that sentence; I think you are
asking how to take someone off hold? Simply send a re-INVITE with the
connection address non-zero once more.

>    --- Ack (media) -------->  B

Assuming (media) means non-zero address, yes.

Note that hold is not necessarily bi-directional, if A sends an INVITE
to B with a zero IP address, B won't send media to A, and is "on hold",
but B is not obligated to return zero in the response. 

-Jonathan R.

-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
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---

From: Dave Walker <[email-masked]>
Date: Thu, 22 Jun 2000 14:32:56 -0400

If it were bi-directional, then how would you get to hear how 
wonderful company X is when someone you phoned there puts you on
hold?  In other words, MOH doesn't work very well with bi-directional
hold.  On the other hand, it'd be nice for my app to automatically 
switch over to my own MOH when I'm on hold.  But then maybe I'd miss 
important information from the far end (like "there are approximately 
20 people before you in the queue", or like "press pound or else I'm 
going to drop your call" - pound to be sent in an INFO of course).

Dave Walker
(who enjoys being on hold)

Jonathan Rosenberg wrote:
[snip]

---

From: "Brett Tate" <[email-masked]>
Date: Thu, 22 Jun 2000 16:59:11 -0400

Thanks for the response.  

A rewording of the question is presented within the following text.

----- Original Message ----- 
From: Jonathan Rosenberg <[email-masked]>
To: Brett Tate <[email-masked]>
Cc: SIPbell-labs <[email-masked]>
Sent: Thursday, June 22, 2000 12:52 PM
Subject: Re: [SIP] Hold & then re-INVITE without media

> Assuming (media) means non-zero address, yes.

I think you already answered my question, but maybe this
will provide some clarity.  

For the following question, assume A originally 
sent the INVITE containing an SDP 
with connection address 0.0.0.0 to B; B replied with 200; 
A replied with an ACK.  Can an INVITE without SDP 
indicate to B that A is no longer "holding B" and will 
provide the complete SDP in the ACK?

A --------------- Invite (no SDP) ----------------------------> B
  <-- 200 (SDP with connection address not 0.0.0.0) ---
    --- Ack (SDP with connection address not 0.0.0.0) -->

---

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 23 Jun 2000 01:25:03 -0400

>     --- Ack (SDP with connection address not 0.0.0.0) -->

This should work. This behavior (no SDP in INVITE, but SDP in ACK) is
allowed, actually. Its main use is for the first INVITE, for interop
with H.323v1 amongst other things. However, if you can do something in a
first INVITE, it is allowed in a re-INVITE, so there you go.

-Jonathan R.