Configuring H.323 - HP FlexNetwork MSR Series Configuration Manual

Configuring H.323

H.323 is an application-layer control protocol for establishing and terminating multimedia sessions
with one or more participants. H.323 can dynamically adjust and modify session attributes, such as
required session bandwidth, media type (voice and video), encoding/decoding format of media, and
support for broadcast.
H.323 uses the Client/Server model to establish calls through communication between the gateway
and gatekeeper.
H.323, a packet-based multimedia communications system, is an ITU-T standard that specifies the
components, protocols, and procedures that provide multimedia communication services over an IP
network that does not provide guaranteed quality of service (QoS). As one of the standards for VoIP,
H.323 has long been used by traditional carriers and network device manufacturers in their VoIP
solutions.
As shown in
includes these protocols:
•
H.225.0, including Q.931 and registration, administration and status (RAS) protocol, and H.245
for signaling control
•
G.711, G.729, G.723.1, and G.723.A for audio codec
•
H.261 and H.263 for video codec
•
T.120 series (including T.123, T.124, T.125, T.126, T.127, and T.324) for multimedia data
transmission.
The real-time transport protocol (RTP) provides end-to-end real-time audio and video delivery
services. Its functionality is enhanced through its control protocol, the real-time transport control
protocol (RTCP). The primary function of RTCP is to provide feedback on the quality of data
distribution, which allows the application system to accommodate to different network conditions and
helps with fault location and diagnosis as well. These two protocols work together to ensure real-time
voice transmission.
Figure 65
illustrates the H.323 stack:
Figure 65 H.323 stack
Data
T.126
T.126 T.324
T.124 T.125 T.324
T.124 T.125 T.123
T.123
ITU-T RAS is implemented in compliance with the H.323v2 protocol for communication between
gateway and gatekeeper. RAS adopts the communication model where a gateway sends requests
and the gatekeeper responds with confirms or rejects listed in the following table.
Figure 65, the H.323 stack is implemented at the application layer. The H.323 standard
Signaling
T.127
H.245
T.127
H.225.0
H.245
RAS
H.225.0
RAS
TCP
TCP Network layer
Link layer
网络层
Physical layer
链路层
Audio Video
G.711
G.729 H.261
G.711
G.723.1 H.263
G.729 H.261
G.723.A
G.723.1 H.263
G.723.A
RTP RTCP
UDP RTP RTCP
UDP
216