Subject: RE: Sendonly in SDP

From: Peter Ford <[email-masked]>
Date: Tue, 7 Mar 2000 14:05:08 -0800

how about a host name and a port? or a URI? ....

cheers, peterf

-----Original Message-----
From: Jonathan Rosenberg [mailto:[email-masked]]
Sent: Tuesday, March 07, 2000 8:38 AM
To: [email-masked]
Cc: Gonzalo Camarillo; mmusic; sip
Subject: Re: Sendonly in SDP

[email-masked] wrote:
> 
> * For send-only streams, the address and port number have no significance
> and SHOULD be set to zero.*

This is true now, but we have just recently realized this is not
correct. The reason is RTCP - the SDP needs to convey the address where
the recipient can send RTCP to. As a result, I think we do need to
include an IP address and port. I think the port should be an even one
(indicating where RTP would be received on, even though no RTP will ever
be received), for consistency. RTCP would be sent to the port one
higher.

-Jonathan R.

-- 
Jonathan D. Rosenberg                       200 Executive Drive
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dynamicsoft                                 West Orange, NJ 07052
[email-masked]                     FAX:   (732) 741-4778
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---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 08 Mar 2000 00:15:16 -0500

> how about a host name and a port? or a URI? ....

SDP does allow a host name to appear in the c line for the address,
although I haven't seen that done much, and I'm not sure how useful it
is. This address needs to be the address of the machine receiving the
media. For many users today, these machines are dial-up or on internal
networks and often have no host name entries in DNS.

As for a URI, SDP simply doesn't allow it. I'm not sure what it would
mean for the media destination to be a URI.

Gonzalo wrote:
> Also about appendix B. If we want to put the other party on hold we will
> set the "c" line to zero.
> 
> Shouldn't we add "a=recvonly" to indicate that we are not going to send
> any packets either?
> 

Doesn't much matter, I guess. The semantic is derived from the port
number.

-Jonathan R.