Voice-mail System using SIP/RTSP

1
Unified Messaging using SIP and RTSP
Kundan Singh and Henning Schulzrinne, Columbia
University

• Agenda
• Introduction
• Requirements
• Architecture
• Issues
• Implementation
• Q/A

2
Traditional voice mail system
Bob can listen to his voice mails by dialing some
number.
3
Problems

• Voice mail system tied to PBX or phone company
  (if CFB)
• Integration of video, fax, whiteboard?
• How to integrate with Internet telephony?
• How to integrate with email, web and other user
  applications?

4
Existing solutions

• Voice Profile for Internet Messaging (VPIM)
• Web-based unified messaging systems with
  personalized PSTN voice mail number.

5
Design Goals

• Message recording and playback
• Universal access web, email, VoIP, PSTN
• Email notification
• Scalability for large domains
• Separable from ITSP or ISP
• Reuse existing infrastructure
• Media-agnostic
• Tool-agnostic
• Telephony interface - DTMF

6
Why SIP and RTSP ?

• Use SIP for accepting voice/video calls (other
  services, and infrastructure for Internet
  telephony)
• RTSP for storage and access of voice messages.
• RTSP already in common use, e.g., RealPlayer
• Large-scale RTSP MoD servers exist.
• Easy integration with web, email, video and fax.
• Access from PSTN using a gateway.

7
Architecture
vm.office.com
The voice mail server registers with the SIP
proxy, sipd, on behalf of every user.
Alice calls bob_at_office.com through SIP proxy.
SIP proxy forks the request to Bobs phone as
well as to a voicemail server.
8
Architecture
v-mail
vm.office.com
After 10 seconds vm contacts the RTSP server for
recording.
vm accepts the call.
Sipd cancels the other branch and ...
rtspd
...accepts the call from Alice.
Now user message gets recorded
9
Architecture
BYE
RTP
200 OK
v-mail
vm.office.com
Once the call is closed by Alice, vm sends
an email to Bob informing him of the arrival of a
voice mail.
10
Architecture
RTP
v-mail
vm.office.com
Bob can listen to voice mail using either an
RTSP client like QuickTime or ...
...by calling the v-mail using SIP.
rtspd
or by visiting his web-based voicemail account
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ArchitectureAlternatives

• The SIP phone redirects the call to voice mail
  after 10 seconds.
• The SIP proxy is configured to forward the call
  to voice mail if your phone is busy or there is
  no response (static, or using sip-cgi, CPL)
• Voice mail server acts as another phone for the
  user but delays accepting the call by 10 seconds,
  with CANCEL if user picks up.

12
Issues

• Call reclaiming
• Deleting voice/video mail
• Integration with PSTN phone
• Integration with VPIM, IMAP, POP3

13
Implementation

• Prototype system.
• Recording and playback using .au files.

http//www.cs.columbia.edu/vmail
14
ImplementationFeatures

• Integration with web/email for more control over
  voicemail configuration (e.g., folder management,
  email notification.)
• Web based voice mail accounts for users (Similar
  to Hotmail)
• Retrieval using RTSP clients (Quicktime), SIP
  user agent (ephone) or Web browser.

15
ImplementationFuture

• DTMF based navigation
• Support for other media formats in rtspd
• Deployment
• Multimedia mail SIP retrieval

16
Conclusion

• SIP and RTSP - good framework for unified
  messaging
• Integration of voice/video mail/answering
  machine, email, instant messaging, fax, etc.

17
ConclusionWide range of applicability
Campus/corporate network
External application service provider
Within a domain