User Manual - Configuration Guide (Volume 3)
Versatile Routing Platform Chapter 1
VoIP Configuration
1-3
feedback, the application system can adapt to different network environm ent. The
feedback on the quality of transmission is also helpful for the fault locati on and
diagnosis.
H.323 Protocol stack
Physical Layer
Link Layer
Network Layer
TCP UDP
T.123 RTP, RTCP
T.124, T.125
T.324
T.126 T.127
H.245
H.225.0
RAS
G.711
G.729
G.723.1
G.723.A
H.261
H.263
Data Signaling Audio Video
Figure VC-1-3 H.323 protocol stack

III. A typical telephone call processing by VoIP

Before configuring the voice function for router, please firstly learn th e rel ev ant f lo w of
the Application Program Layer for the smooth configuration.
1) User picks up the hook and the voice interface board detects the ac tion. Then the
board transmits this signal to the VoIP signal processing part over the router.
2) The VoIP Ses sion Application Program plays the dialing tone and waits for the
user to dial.
3) T he user begins to dial, and the VoIP s ession application program collects and
stores the dialed number.
4) After collecting enough number to match a configured destination mode, t he
number will be mapped to an IP host through a dial plan mapper. The IP host
directly connects with the target telephone or the PBX. If the PBX is connected,
PBX will accomplish the remaining part of the call.
5) The VoIP s ession application progr am uses the H.323 protocol to tra nsmit and
receive voice data channel for the connection in each direction over the IP network.
If the PBX is to processes a call, it will forward the call to the destination telephone.
6) The agreed codec mode is enabled at both ends of connection, which uses the
RTP/UDP/IP as protocol stack to continue the session.
7) Once the end-to-end RTP voice channel is established, the prompt signals of all
the calling procedures and the signals that can be transmitted in the band are
transported through this channel over the IP network. RTCP packet is used to
transmit such information as the transmission quality of voice data in the ca lling
session.
8) When one calling party is on-hook, the session ends, and both ends resume the
idle state and wait for a new call establishment triggered by the next of f-hook.
1.1.2 IP Voice Implementation over VRP
The router serves as voice gateway to provide voice functions, which makes data
conversion from the circuit-switching network to the packet-switching n etwork . During
the conversion, you need to convert the phone numbers to the IP addresses that the