Cisco AS5350XM Configuration Manual page 151

Configuring Voice over IP
The information in this chapter applies to the Cisco AS5350XM and Cisco AS5400XM universal
gateways.
Voice over IP (VoIP) technology enables voice-capable routers and switches to transport packetized live
voice traffic such as telephone calls over IP data intranetworks or internetworks rather than public
switched telephone networks (PSTN) or private TDM (PBX) networks. VoIP thus enables toll bypass,
remote PBX presence over WANs, unified voice and data trunking, and plain old telephone service
(POTS)-Internet telephony gateways. VoIP enables more efficient and full use of your existing IP data
network, both reducing transmission costs and possibly your need to support dual (voice and data)
networks.
Routers and switches such as the Cisco AS5350XM and Cisco AS5400XM universal gateways can
handle origination, transport, and termination of VoIP traffic. They digitize analog voice signals,
compress them, package them into a series of discrete packets, and transport them interleaved with data
packets. They can transmit VoIP packets to both VoIP and non-VoIP destinations, and can receive both
VoIP and nonVoIP calls. When data lines are busy, they can spill traffic onto the PSTN.
To ensure acceptable quality of service (QoS) for your voice users, it is important that you configure
your gateway carefully and monitor its performance vigilantly—to ensure, for voice traffic, priority
service with minimal loss and delay. Unlike most other types of data, voice is intolerant of almost any
form of loss or delay. Users cannot wait for a destination device to reorder packets and request that the
sending device retransmit any that are missing, as it does for most other data types.
To configure basic VoIP, in general you need to do the following:
Configure signaling on voice ports
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Configure dial peers
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You might also need to do the following:
Configure voice QoS features
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Configure Frame Relay for VoIP
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Configure the gateway to distinguish between voice and modem calls (necessary when the
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network-access server supports both modem dialup and VoIP users on the same POTS interface)
Optimize dial-peer and network-interface configurations
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Configure VoIP for Microsoft NetMeeting
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