Packetizer

Call flow for third-party pause (Q88)


The information in this article applies to: H.323, H.245

Here is a prototypical call flow written from the point of view of the videoconferencing endpoint that receives an empty termCapSet.

(Typical call is up and running with audio and video in both directions.)

(Remote EP initiates pause.)

<-- TCS (empty: all OPTIONAL ASN.1 components are absent,
            leaving just seqNum and protocolIdentifier)
(Knowledge of the remote EP's capabilities is completely removed, as if the EP never received them.)
--> TCSAck
--> CLC audio
--> CLC video
<-- CLCAck audio
<-- CLCAck video
(EP is paused but still able to receive incoming audio and video. Remote EP could close, reopen, etc. its channels if it wanted to. It could even send another empty TCS.)

(Remote EP initiates "resume," or unpauses the EP.)

<-- TCS (fully populated with possibly different caps than before)
--> TCSAck
--> MSD
<-- MSDAck
--> MSDAck
--> OLC audio
--> OLC video
<-- OLCAck audio
<-- OLCAck video
(Call is now re-established with audio and video in both directions.)