H.323 – a signaling
H.323 standards were generally the first to classify and solve multimedia delivery issues overin solving existing problems, but it is fair to say that the RFC process of furthering the standards has had greater success than the H.323 counterparts.
H.323 networks consist of
H.323 specifications tend to be heavier (due to chattiness, in terms of control signaling) and with an initial focus in LAN networking. These standards have some shortcomings in scalability, especially in large-scale deployments. Primarily, limitations are due to chattiness or the heavy signaling required to establish H.323 sessions. H.323 is dependent onTCP sessions because of the substantial overhead involved. However, most H.323 scalability limitations are based on the prevalent version two of the specification. Subsequent versions of H.323 have a focus on solving some of these problems.
Let’s look at the main H.323 process:
- With each call that is initiated, a TCP session (H.225.0 protocol) is created, using an encapsulation of a subset of Q.931 messages. This TCP connection is maintained for the duration of the call. Complete call setup process is shown in figure 5.
- A second session is established using the H.245 protocol. This TCP-based process is for capabilities exchange, master-slave determination, and the establishment and release of media streams. This group of procedures is in addition to the H.225.0 processes.
- The H.323 RSVP). This protocol is not considered to have good scaling properties due to its focus and management of individual
- Although H.323 may not be well suited in service provider spaces, it is well positioned to deploy enterprise VoIP applications. As a service provider, it might be necessary to bridge, transport or interface H.323 services and applications to the PSTN.