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CHAPTER
3-1
Cisco IOS XE Integrated Session Border Controller Configuration Guide for the Cisco ASR 1000 Series Aggregation Services Routers
OL-15421-01
3
DTMF Interworking
This chapter describes the importance and function of dual-tone multifrequency (DTMF) interworking
between various signaling types and how DTMF is supported on the Integrated Session Border
Controller.
For a complete description of commands used in this chapter, refer to the Cisco IOS Integrated Session
Border Controller Command Reference.
Contents
• Information About DTMF Interworking, page 3-1
• RTP to SIP Interworking, page 3-2
• SIP to RTP Interworking, page 3-2
• Configuring Default Duration of a DTMF Event, page 3-2
Information About DTMF Interworking
One of the features of the Integrated Session Border Controller is the ability to interwork between the
various dual-tone multifrequency (DTMF) signaling types. DTMF interworking is used when the two
endpoints do not use the same type for relaying DTMF tones.
DTMF dialing consists of simultaneous voice-band tones generated when a button is pressed on a
telephone. The challenge comes from a scenario where one side uses Real-time Transport Protocol (RTP)
and the other uses Session Initiation Protocol (SIP) signaling to enable advanced telephony services.
Examples of the types of services and platforms that are supported by DTMF interworking are various
voice web browser services, Centrex switches or business service platforms, calling card services, and
unified message servers. All of these applications require DTMF interworking for the user to
communicate with the application outside of the media connection.
The Cisco ASR 1000 Series Aggregation Services Routers only support DTMF interworking between
RTP and SIP DTMF indication types. This type of DTMF interworking provides for DTMF signals
generated by SIP to be inserted into an RTP stream and RTP DTMF tones to be extracted and to generate
a SIP message.
The following are ways of generating a DTMF tone:
• SIP digit detection and generation package—A SIP message is sent from the endpoint to the SIP
proxy indicating that there has been a DTMF event, the type and the duration of the event.