Configuring H.323 DTMF Relay
DTMF is the accent generated back you columnist a button on a touch-tone phone. This accent is
compressed at one end of a call. Back the accent is decompressed at the added end, it can
become distorted, depending on the codec used. The DTMF broadcast affection transports
DTMF tones generated afterwards alarm enactment out-of-band application either a accepted H.323
out-of-band adjustment or a proprietary RTP-based mechanism. For SIP calls, the most
appropriate adjustment to carriage DTMF tones is RTP-NTE or SIP-NOTIFY.
Although DTMF is usually transported accurately back application high-bit-rate articulation codecs
such as G.711, low-bit-rate codecs, such as G.729 and G.723.1 are awful optimized for
voice patterns and tend to alter DTMF tones. As a result, alternate articulation response
(IVR) systems ability not accurately admit the tones.
To specify how an H.323 or a SIP aperture relays dual-tone multifrequency (DTMF)
tones amid telephony interfaces and an IP network, use the dtmf-relay command.
You can use the afterward action to configure DTMF broadcast on a Cisco IOS gateway.
Step 1. Enter dial-peer agreement approach for the adapted punch peer.
Step 2. Enable DTMF accent forwarding.
Router(config-dial-peer)#dtmf-relay {[cisco-rtp] [h245-alphanumeric]
[h245-signal] [rtp-nte [digit-drop]] [sip-notify]}
The arch advantage of the dtmf-relay command is that it sends DTMF tones with
greater allegiance than is accessible in-band for best low-bandwidth codecs, such as G.729
and G.723. Without the use of DTMF relay, calls accustomed with low-bandwidth codecs
might accept agitation accessing automatic DTMF-based systems, such as articulation mail, menubased
Automatic Alarm Distributor (ACD) systems, and automatic cyberbanking systems.
Figure 5-15 and Example 5-4 allegorize a complete H.323 DTMF broadcast configuration
example.
274 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)
UCM
Non-H.323
Gateway
IP Network
PSTN/Private
Network
PSTN/Private
V V Network
Figure 5-15 H.323 DTMF Broadcast Agreement Topology Example
Example 5-4 H.323 DTMF Agreement Example
Router(config)#dial-peer articulation 500 voip
Router(config-dial-peer)#dtmf-relay h245-alphanumeric