Focus on H.324

Last week, we introduced you to H.263 as one standard that helps provide video over IP on wires, with the potential to offer video over IP over wireless. Today, we’d like to continue our explanation with another “over IP” standard: H.324.

H.323 is the umbrella standard for multimedia applications over IP, and “323” and has almost become synonymous with legacy VoIP implementations. H.323 was designed with the IP-based LAN (and the WAN) in mind, taking advantage of high-speed communications links.

Like its brother H.323, H.324 is also an umbrella of standards, only it is designed for low-bit-rate communications that operate over the public switched telephone network. H.263, the standard we discussed last week, is a member of the H.324 series, comprising the video piece of the puzzle. Other pieces of the H.324 series include:

* H.223, a multiplexing protocol for multimedia terminals.

* H.245, a communications control protocol for multimedia terminals.

* G.723.1, a speech-encoding standard for transmitting at 5.3/6.3K bit/sec.

H.324 is important for several reasons. First, as a suite of standards, it provides a common way for a multimedia user’s multiple systems components and vendors to work together. Second, it is designed for low bit rates (the still-dominant connectivity range), so the broadest possible number of users can benefit from H.324-based interoperability. Finally, it has provided a baseline for other work, including H.324M and 3G.324M. We’ll talk about this standards evolution to mobile environments next time.