Conveying Tones in SIP: IETF 57, SIPPING

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Conveying Tones in SIPIETF 57, SIPPING

• Rohan Mahy

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How can you provide tones?

• In RTP
• speech codec poor choice
• using audio/tone AVT payload
• using audio/telephone-event AVT payload
• Referenced externally by URI with Alert-Info or
  message/external
• In a SIP header (proposed back in Nov 2000)
• In the Session Description?
• In the body of the SIP message
• Content-Disposition render
• Possibly tagged with Content-ID and cid URI in
  Alert-Info header

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What body types are available?

• traditional audio mime types
• wav, au, mp3, etc..., MIDI
• audio/tone
• audio/telephone-event
• audio/tone-infoxml
• other tone descriptions
• just a ringback-specific description
• country code or tone list

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What would an XML tone description look like?
Content-Type audio/tone-infoxml Content-Disposit
ion renderhandlingoptional Content-ID
foo_at_bar lt?xml version"1.0" ?gt lttones
repeat"true"gt lttonegt ltmodulation hz"0"/gt
ltvolume db"-3"/gt ltduration ms"2000"/gt
ltfrequency hz"440"/gt ltfrequency hz"480"/gt
lt/tonegt lttonegt ltmodulation hz"0"/gt
ltvolume db"-63"/gt ltduration ms"4000"/gt
ltfrequency hz"0"/gt lt/tonegt lt/tones
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What would ringback-specific description look
like?

• modulated ringing
• dual tone
• continuous
• custom
• silence

Country au Ringback 400x170.40.20.42
Country us Ringback 44048024
Country tz Ringback 40010
Country us Ringback 4404800.50.514
Ringback 000
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Conclusion

• Using explicit tones can convey country-specific
  tones such as ringback, including silence (which
  would prevent local ringback)
• Hopefully this can reduce the occurence of early
  media which is just ringback, and possibly other
  tones (like two-stage dialing tones)
• Is this interesting to the working group? What do
  we do with this?