Title: Reliable, Scalable and Interoperable Internet Telephony

Speaker: Dr. Kundan Singh

URL: http://www.cs.columbia.edu/~kns10/publication/

Abstract:

The public switched telephone network (PSTN) provides ubiquitous
availability and very high scalability of more than a million busy
hour call attempts per switch.  If large carriers are to adopt
Internet telephony, then Internet telephony servers should offer at
least similar quantifiable guarantees. I present a reliable, scalable
and interoperable Internet telephony architecture for user
registration, call routing, conferencing and unified messaging using
commodity hardware. The results extend beyond Internet telephony to
encompass multimedia communication in general.

The architecture deals with two aspects: at least PSTN-grade
reliability and scalability of the Internet telephony servers, and
interoperable Internet telephony services such as conferencing and
voice mail using existing protocols. I describe Columbia InterNet
Extensible Multimedia Architecture (CINEMA) that consists of a
registration and proxy server, a multi-party conferencing server, an
interactive voice response system and a multimedia mail server. CINEMA
facilitates collaboration using synchronous communications like
multimedia conferencing, instant messaging, shared web-browsing,
asynchronous communications like discussion forum, shared files, voice
and video mails, and seamless integration with telephone, IP phone,
web and electronic mail.

I present two techniques for providing scalability and reliability in
the Session Initiation Protocol (SIP): server redundancy and a novel
peer-to-peer architecture. For the former, I use DNS-based load
sharing among multiple distributed servers that use backend SQL
databases to maintain user records. The two-stage architecture scales
linearly with the number of servers. For the latter, I describe a
peer-to-peer Internet telephony architecture that supports basic user
registration and call setup as well as advanced services such as
offline message delivery, voice mail and multi-party conferencing
using SIP. It interworks with server-based SIP infrastructures.

Finally, I present some of the scalability, robustness and performance
challenges in an Internet-wide web-based video telephony platform.