H.323 Fast Connect Call Setup
Figure 5-10 shows an H.323 setup exchange that uses the Fast Connect abbreviated procedure
available in version 2 of ITU-T Recommendation H.323.
The Fast Connect procedure reduces the number of round-trip exchanges and achieves
the capability exchange and logical channel assignments in one round trip.
The Fast Connect procedure includes these steps:
1. The originating gateway initiates an H.225.0 session with the destination gateway on
registered TCP port 1720.
2. Call setup procedures based on Q.931 create a combined call-signaling channel and
control channel for H.245. Capabilities and logical channel descriptions are
exchanged within the Q.931 call setup procedure.
3. Logical channel descriptions open RTP sessions.
4. The endpoints exchange multimedia over the RTP sessions.
H.323
Gateway
1.1.1.1 1.1.1.2
Signaling
Bearer
or
Media
H.225.0/H.245 (TCP)
Media (UDP)
IP
Setup
PSTN PSTN
V V
POTS/PSTN
Call Setup:
Ringing,
Progress,
Answer...
Connect