inactive field on SDP while putting call on hold

Joined: Tue 07 of Jul, 2015

inactive field on SDP while putting call on hold

Posted:Tue 07 of Jul, 2015 (00:39 UTC)
I hope i am posting this on right thread and not repeating is (I could not find anything on this topic when I searched)

What does "inactive" means in SDP under "media attribute"

I am not best at reading RFC's and could not make much sense of it.

below is from RFC at end.


- two hold music being played back to user when call is put on hold, does not matter which way call was initiated

- calls are being trunked/peer to PBX

- when call is being put on hold I am used to seeing "sendonly" or "reconly". What does "inactive" do ?. I am seeing "inactive" being sent by PBX

(i believe whichever agent sends inactive stays passive ?, then who plays hold music back ?)

- I can see hold music stream coming from PBX as well as, ISP is inserting its own hold music.

FROM RFC 4566 -


This specifies that the tools should be started in inactive
mode. This is necessary for interactive conferences where
users can put other users on hold. No media is sent over an

Handley, et al. Standards Track Page 27

RFC 4566 SDP July 2006

inactive media stream. Note that an RTP-based system SHOULD
still send RTCP, even if started inactive. It can be either a
session or media-level attribute, and it is not dependent on