Configuring Voice over IP
Enabling QoS Features for VoIP
106
Cisco VGD 1T3 Voice Gateway Software Configuration Guide
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 VGD 1T3 voice 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
•
GSMFR
•
G.Clear
Note
Tandem switching (also called dual encodings or dual compressions) can cause additional problems.
Digital calls routed to a tandem (toll) office are converted there to analog form for processing, and then
reconverted to digital form for further transmission. Converting and reconverting in this way more than
about twice distorts signals irreparably. If your calls are subject to significant toll-office processing,
choose PCM if you have sufficient bandwidth. We also recommend that you employ a Cisco IOS
Multimedia Conference Manager (H.323 gatekeeper) or management application such as Cisco Voice
Manager to help manage these types of processes.
Other factors that might enter into your decision, or that you can use to tweak performance, include the
likelihood of multiple tandem encodings and how you handle packet fragmentation.
Tip
For more information and configuration options, see the VoIP over PPP Links with Quality of Service
(LLQ / IP RTP Priority, LFI, cRTP) document, available online at
http://www.cisco.com/warp/public/788/voice-qos/voip-mlppp.html.
Содержание VGD-1T3
Страница 10: ...Contents x Cisco VGD 1T3 Voice Gateway Software Configuration Guide ...
Страница 14: ...Notices OpenSSL Open SSL Project 4 Cisco VGD 1T3 Voice Gateway Software Configuration Guide ...
Страница 120: ...Configuring Voice over IP Additional Resources 110 Cisco VGD 1T3 Voice Gateway Software Configuration Guide ...
Страница 196: ...Using the Setup Script Where to Go Next 186 Cisco VGD 1T3 Voice Gateway Software Configuration Guide ...