Configuring Voice over IP
Enabling QoS Features for VoIP
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Cisco AS5350XM and Cisco AS5400XM Universal Gateways Software Configuration Guide
a low-bandwidth (< 1.5 Mbps) WAN circuit, but not if you have a high-bandwidth (> 1.5 Mbps) WAN
circuit. The recommended fragmentation and interleaving methodology is FRF.12 for Voice over Frame
Relay, Multilink PPP for VoIP-over-PPP leased lines.
Tip For more information and configuration options, see the following:
• For FRF.12, Frame Relay Fragmentation for Voice, available online at
http://www.cisco.com/warp/public/788/vofr/fr_frag.html
• For Multilink PPP, VoIP over PPP Links with Quality of Service (LLQ / IP RTP Priority, LFI, cRTP),
available online at
http://www.cisco.com/warp/public/788/voice-qos/voip-mlppp.html
Traffic Shaping for Frame Relay
You must regulate traffic flow so that packets arrive at their destination only as fast as the destination
can handle them. You do so by buffering packets that are generated faster than a configured value, and
releasing them at that value. It is especially important that you enable traffic shaping in Frame Relay
networks, but not in conjunction with RSVP. Do not enable traffic shaping with PPP leased lines.
Tip For more information and configuration options, see the VoIP over Frame Relay with Quality of Service
(Fragmentation, Traffic Shaping, IP RTP Priority document, available online at
http://www.cisco.com/warp/public/788/voice-qos/voip-ov-fr-qos.html
Note Successful traffic shaping on a Frame Relay network requires that you set not just this but many other
QoS features. See these references and the “Additional Resources” section for more information.
Other Bandwidth-Reduction Features
Voice Encoding
The Cisco AS5350XM and Cisco AS5400XM universal gateways offer multiple codec (coders/decoder)
methodologies for encoding (digitizing and, optionally, compressing) voice:
• G.711
• G.723.1
• G.726
• G.729
• G.729a
• G.729ab
• G.729b
• GSMAMR-NB
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