Session Initiation Protocol (SIP) - a justifiable cause for optimism

"The continuing rapid development and adoption of Session Initiation Protocol (SIP) is justifiable cause for optimism amongst service providers and enterprises alike," says Andy Bull, director for Mitel Networks Limited South Africa.

SIP is a standards and text-based, peer-to-peer based protocol, developed by the IETF that facilitates openness, connectivity, simplicity, choice and personalisation. Operating at the application layer, it provides signalling and session management within the packet network for two or more end points. SIP uses fewer resources and is considerably less complex than H.323 the signalling protocol currently used in VoIP and Video conferencing systems.

"As the emerging protocol of choice for setting up telephony, multimedia, conferencing, and other kinds of communications sessions on the Internet, SIP enables delivery of advanced, value-added services that are expected to dramatically boost bandwidth utilisation and revenue," says Bull.

Some leading service providers have already committed to and are beginning to deliver SIP-based service offerings, while growing legions of developers are hot on the trail of the next generation of killer applications that SIP will support.

Bull says the key reason why SIP will serve as an integral part of tomorrow` s VoIP landscape is that it offers a straightforward approach to deliver the VoIP services enterprises and service providers both need.

Essentially, SIP follows the same development path that the Internet and private IP networks have followed since TCP/IP networking was first developed: intelligence is pushed to the edge. This makes it possible for SIP to deliver key benefits such as an open system for developing and deploying applications and services beyond voice, such as the exchange of data. Other key benefits include presence management services that determine the availability and level of accessibility of the target end point as well as eased manageability and service creation.

"Moreover, these capabilities have caught on with service providers and technology developers and vendors, many of whom have thrown a good deal of support behind SIP," says Bull. Since SIP facilitates a simple, open, standardised form of VoIP connectivity, Bull says these vendors and service providers will develop and market a broad array of SIP services and products that will deliver the applications and "communications personalisation" packetised telephony has long promised.

As has been said before, a key element to VoIP`s appeal is its applications. "However, deploying converged applications can quickly result in network overhead that can potentially impair the quality of packetised voice communications," says Bull.

Being an ASCII-based application protocol, SIP offers a more streamlined approach to deploying new applications. Moreover, SIP also includes the presence management capabilities, a key element in converged applications. Presence management not only lets users employ a variety of means to communication, but also ensure that each user is employing the communication method most suitable to his or her current needs.

SIP`s application and presence capabilities could make new communications exchanges possible. For example, by using SIP, a manager seeing an employee engaged in a conversation with a key client, could join the call, and turn a two-way call into a more effective and responsive conference call. Alternatively, two users engaged in a SIP conversation could also share small data flows such as scheduling information or personal contact information with one another. These two users could then refer to a directory of multiple users and synchronise each user`s schedule to set up a conference call. SIP`s presence management capabilities could then ensure that each user is reached on the date of the conference. That group of users could then send instant messages to one another prior to the meeting to prepare materials, determine responsibilities, etc.

"While SIP enables a wide range of new services using a networking approach that is more manageable that previous circuit-switched systems, there are areas that need addressing in order to ensure that SIP lives up to the expectations of services providers, enterprise user and residential users," says Bull.

"These include support for enhanced 911 (E911) services, providing power through the LAN, ensuring secure voice communications, building quality, dependable end user devices as well as ensuring ease of management," concludes Bull.