SIP video conferencing systems: A standardized approach to integration

The growing popularity of Session Initiation Protocol (SIP) has led video conferencing vendors to move to adopt SIP for system and endpoint integration. As SIP-based video conferencing systems become more common, the systems can more easily integrate into unified communications (UC), sharing presence information across applications or enabling users to initiate video conferencing sessions from smartphones and desktop UC clients.

In part four of our Expert Lesson on video conferencing, Katherine Trost, research analyst with Nemertes Research, discusses how adopting SIP video conferencing systems sets the groundwork for interoperable voice, video and collaborative applications that make up the key elements of UC architecture.

SIP video conferencing systems: A standardized approach to integration

by Katherine Trost, Research Analyst, Nemertes Research

The role of SIP is straightforward: It enables endpoints to find one another, establish a session and terminate the session once communication is complete. As defined in IETF Request for Comments (RFC) 3261, SIP provides a common signaling language for any kind of rich media session, be it voice, video or instant messaging (the latter via SIMPLE -- SIP for Instant Messaging and Presence Leveraging Extensions).

SIP actually comprises two protocols -- SIP for initiating and terminating a session between endpoints, and the Session Description Protocol (SDP) for defining the type of session (e.g., voice or video) and session parameters such as codecs or encryption. Since SDP allows application developers to leverage any pre-existing encapsulation protocol, most SIP implementations use the same protocols as H.323 , whether they are voice codecs such asG.711, G.722 or G.729; video codecs, including H.261 and H.264; or other supported media encapsulation types.

SIP-based video conferencing systems can easily integrate into UC, sharing presence information across applications (for example, allowing one user to see when another is in a video conference). Video conferencing vendors can also take advantage of the other benefits of SIP vs. H.323, including reduced endpoint and architectural complexity, easier management and greater extensibility.

Adoption of SIP video conferencing systems also means greater likelihood of interoperable conferencing across enterprise boundaries, either by organizations that establish direct interconnectivity between systems, or for those wishing to leverage hosted/managed services to support extranet conferencing.

SIP-enabled hosted voice and video integration

Hosted services for voice and video interconnectivity, as well as hosted video conferencing services, are also based largely on SIP, meaning SIP has emerged as not only the protocol of choice for internal systems, but also as the standard for interconnecting internal systems with hosted or external applications.

Video as a component of UC means that enterprise IT architects must coordinate video conferencing planning with those within their organization responsible for UC initiatives. The ability of video conferencing systems to integrate withUC dashboard applications from vendors, including IBM Lotus and Microsoft, becomes increasingly important as an evaluation criterion as well. Those planning for coming desktop video rollouts must ensure that their efforts integrate, rather than conflict, with UC dashboard applications that have their own desktop video conferencingcapabilities.

But SIP use also comes with a word of caution: Just standardizing on SIP is not enough to reduce integration headaches. As we noted earlier, video conferencing sessions make use of an extensive suite of protocols for encapsulationof voice and video, as well as supporting features such as encryption and management. For example, a Microsoft video conferencing client using SIP for signaling but a proprietary video codec for video encapsulation cannot connect to an endpoint using SIP for signaling but an open standard like H.264 for video encapsulation.

Many organizations have large deployments of legacy systems, and this requires either upgrading or the purchasing of gateways to enable them to function in a SIP-based video conferencing environment. Forklift upgrades, additional gateway purchases or even software upgrades may not be feasible, given tight IT budgets.

Thus, the ideal approach is to create an architecture that is capable of interoperable support of existing protocols in use (e.g., SIP, H.323 or vendor proprietary alternatives) during the time of transition to SIP video conferencing systems. This strategy will reduce integration complexity by allowing IT architects to support a wider range of existing protocols for as long as necessary.

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