Fragmentation And Interleaving; Traffic Shaping For Frame Relay - Cisco AS5350 - Universal Access Server Configuration Manual

Chapter 6 Configuring Voice over IP

Fragmentation and Interleaving

Transmission of voice packets, usually small (60 to 240 bytes) in size, can be unduly delayed in networks
that also transmit large data packets. Fragmenting large data packets into smaller ones and interleaving
voice packets among the fragments reduces jitter and delay. Use fragmentation and interleaving in
conjunction with a congestion-management technique such as IP RTP Priority and/or RSVP if you have
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.
For more information and configuration options, see the following:
Tip
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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.
For more information and configuration options, see the following:
Tip
•
•
Successful traffic shaping on a Frame Relay network requires that you set not just this but many other
Note
QoS features. Refer to these references and the
OL-3418-02 B0
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, Voice over IP Quality of Service for Low-Speed PPP Links, available online at
http://www.cisco.com/warp/public/788/voice-qos/voip-mlppp.html
VoIP over Frame Relay with Quality of Service (Fragmentation, Traffic Shaping, IP RTP Priority,
available online at
http://www.cisco.com/warp/public/788/voice-qos/voip-ov-fr-qos.html
Frame Relay Traffic Shaping for Voice, available online at
http://www-vdtl/SPUniv/Vofr/FR_traffic.htm
Cisco AS5350 and Cisco AS5400 Universal Gateway Software Configuration Guide
"Additional Resources" section for more information.
Enabling QoS Features for VoIP
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