Ringback Tones In Sip-Based Telephony

Ringback tones in SIP-Based Telephony



This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.

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Abstract

This document describes a mechanism by which an appropriate
ringback tone maybe played to the calling party when the called
party's device is alerting. It is written specifcally to address
the case where the Session Initiation Protocol (SIP) is used to
initiate voice-over-IP calls. It also lists ringback
characteristics for several countries.

1.Introduction

In the current PSTN (public switched telephony network), users
expect to hear an appropriate ringback tone when contacting a
node in a foreign network. For example, when placing a call from
the United States to Sweden, a Swedish ringback tone is heard by
thecaller.

Further, it is currently possible that calls terminating on a PBX
exchange receive special ringback tones which are distinct from
those used by the PSTN in the country in which the PBX resides.



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Internet Draft Ringback tones in SIP-Based Telephony November 2000



In order to ease the transition from standard circuit-switched
telephony to voice-over-IP telephony, it is desirable that, when
feasable, userexperience remains largely the same. In the case
of providing an appropriate ringback tone, doing so is quite
trivial.

This document defines two extension headers to SIP [1] to allow
such behavior. The first, "Country," specifies the country in
which the called party islocated. The second, "Ringback," allows
the called party to give an specific frequency and cadence for
the ringback tone. Both headers are expected to be included only
in "180 Ringing" responses to "INVITE" requests.

2. Client Handling

If a SIP UAS (called...