Multiservice Networking, IPX Networking, and Security - CCIE Routing and Switching Exam Certification Guide - page 551

Codec Standards Table 12-2

Codec Bit Rate Description

G.711u 64 kbps Pulse code modulation (PCM); mu-law version in North America

and Japan; samples speech 8000 times per second, represented in
8 bytes

G.711a 64 kbps PCM; a-law in Europe and in international routes

G.723.1 6.3 kbps MPE-MLQ (Multi-Pulse Excitation-Maximum Likelihood

Quantization)

G.723.1 5.3 kbps ACELP (algebraic code excited linear prediction)

G.726 16/24/ 32/40 kbps Adaptive differential pulse code modulation (AD-PCM)

G.729 8 kbps CS-ACELP (Conjugate Structure ACELP)

H.323

H.323 is a standard that is published by the International Telecommunication Union (ITU) that
works as a framework document for multimedia protocols, which includes voice, video, and
data conferencing for use over packet-switched networks. H.323 describes terminals and other
entities (such as gatekeepers) that provide multimedia applications.

H.323 includes the following elements:
•

Terminals —Telephones, video phones, and voice mail systems

•

Multipoint Control Units (MCU) —Responsible for managing multipoint conferences

•

Gateways —Composed of a Media Gateway Controller for call signaling and a Media
Gateway to handle media

•

Gatekeeper —Optional component for admission control and address resolution

•

Border Elements —Collocated with the gatekeepers; provides addressing resolution and
participates in call authorization

H.323 terminals must support the following standards:
•

H.245

•

Q.931

•

H.225

•

RTP/RTCP

H.245 specifies messages for opening and closing channels for media streams, other
commands, requests, and indications. It is a conferencing control protocol.