SIP APIs for Voice and Video Communications on the Web

TL;DR

This paper proposes a new architecture for real-time voice and video communication on the web, using an adaptor application, SIP-inspired APIs, and UDP media paths to overcome current protocol limitations.

Contribution

It introduces an open architecture with a RESTful API, session description metadata, and UDP media paths, enabling web-based real-time communication with easy codec and NAT traversal support.

Findings

Developed an open source prototype for web-based conference communication.

Demonstrated the feasibility of using an adaptor approach for real-time media.

Enhanced compatibility with SIP systems and web standards.

Abstract

Existing standard protocols for the web and Internet telephony fail to deliver real-time interactive communication from within a web browser. In particular, the client-server web protocol over reliable TCP is not always suitable for end-to-end low latency media path needed for interactive voice and video communication. To solve this, we compare the available platform options using the existing technologies such as modifying the web programming language and protocol, using an existing web browser plugin, and a separate host resident application that the web browser can talk to. We argue that using a separate application as an adaptor is a promising short term as well as long-term strategy for voice and video communications on the web. Our project aims at developing the open technology and sample implementations for web-based real-time voice and video communication applications. We describe the architecture of our project including (1) a RESTful web communication API over HTTP inspired by SIP message flows, (2) a web-friendly set of metadata for session description, and (3) an UDP-based end-to-end media path. All other telephony functions reside in the web application itself and/or in web feature servers. The adaptor approach allows us to easily add new voice and video codecs and NAT traversal technologies such as Host Identity Protocol. We want to make web-based communication accessible to millions of web developers, maximize the end user experience and security, and preserve the huge global investment in and experience from SIP systems while adhering to web standards and development tools as much as possible. We have created an open source prototype that allows you to freely use the conference application by directing a browser to the conference URL.