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Configuring Subscriber-End Broadband Access Router Features
Voice over IP Operations
MC-618
Cisco IOS Multiservice Applications Configuration Guide
Figure 113 Simplified VoIP over Cable Network
You can deploy IP telephony as a local-loop bypass service where voice packets are transferred from the
CMTS to one of the following, depending on the signalling protocol used:
• A telephony gatekeeper when using H.323; the Cisco uBR924 acts as an H.323 gateway.
• A call agent when using SGCP.
The gatekeeper or call agents manage voice calls; the gateway interconnects the IP network to the Public
Switched Telephone Network (PSTN). The gatekeeper must be running Cisco IOS Release 12.1 or later
in order to support registration of the full E.164 address for each Cisco uBR924 port.
Voice calls are digitized, encoded, compressed, and packetized in the originating gateway, then
decompressed, decoded, and reassembled in the destination gateway. A server maintains subscriber
profiles and policy information.
You can place and receive calls without using the local exchange carrier. Two simultaneous voice and
fax calls are supported to and from each subscriber site. Multiple telephones and fax devices can be
connected to each of the two VoIP telephone lines at a subscriber site, providing the 5 REN limit is
adhered to for each telephone line.
Note the following requirements and characteristics of VoIP applications using the Cisco uBR924 cable
access router:
• The telephones at each subscriber site must support touch-tone dialing; rotary dialing is not
supported.
• Special telephone features such as call waiting, call forwarding, and conferencing are not supported.
• A two-line telephone can be connected to the V1+V2 port on the Cisco uBR924.
18194
Gatekeeper or
calling agents
Service
provider
backbone
HFC
cable plant
HFC
cable plant
Cisco uBR924
Cisco uBR924
CMTS rack
equipment
CMTS rack
equipment
Gateway/PSTN
Calling party
Residence or SOHO
subscriber site 1
Residence or SOHO
subscriber site 2
Called party
Policy
server