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Cisco uBR924 Software Configuration Guide
OL-0337-05 (8/2002)
Chapter 4 Voice over IP Configurations
Overview
Introduction
The Cisco uBR924 router uses packets to transmit and receive digitized voice over an IP network. Voice
traffic is supported in both the DOCSIS-bridging and routing modes.
Note When the router is acting in DOCSIS-bridging mode, a voice call originating from the router’s Ethernet
interface cannot terminate on another device attached to that same Ethernet interface; it must terminate
on a device that is reached through the cable interface. The router must be operating in routing mode to
allow calls to both originate and terminate on the Ethernet interface.
Voice signals are packetized and transported in compliance with the following protocols:
• H.323v2—Second version of an International Telecommunications Union (ITU) standard that
specifies call signaling and control protocols for an IP data network. Supported on Cisco IOS
Release 12.0(4)XI and higher voice images.
• Simple Gateway Control Protocol (SGCP) Version 1.1—A signaling protocol under review by the
Internet Engineering Task Force (IETF). Supported on Cisco IOS Release 12.0(7)T and higher voice
images.
• Media Gateway Control Protocol (MGCP) Version 0.1—A proposed IETF voice control protocol
intended to eventually supersede the existing SCGP 1.1 protocol. Supported on Cisco IOS
Release 12.1(3)T and higher voice images.
Note In Cisco IOS Release 12.1(3)T, the MGCP 0.1 and SGCP 1.1 protocols have been merged on the
Cisco uBR924 router so that the router can respond efficiently to either protocol. The MGCP and SGCP
protocols cannot be used if the H.323v2 protocol is used.
Figure 4-1 illustrates a broadband cable system that supports VoIP transmission.