SIP: A Paradigm in Making

At a time when VoIP is waging its battles against a well-entrenched time division multiplexing (TDM) technology paradigm for the telecom equipment market, the emergence of SIP as a VoIP standard is an interesting sub-plot within the overall IP telephony story. 

SIP is a signaling protocol promoted by the IETF for establishing sessions such as a telephone call or a multimedia conference in an IP network. It was approved by IETF as a standard in 1999. Since then, SIP has gained popularity as a scalable and flexible standard for VoIP, among other applications. SIP is a simple technology–it is easy to configure, adapting itself comfortably in different architectures and deployment scenarios. Best of all–SIP closely resembles HTTP and SMTP, the two Internet protocols that drive the hugely popular Web and e-mail. Using SIP, telephony literally becomes yet another Web application.

And here was the most significant catch. For the traditional telecom world, VoIP itself was a shock. A telephone network using Internet technologies was a nightmare. However, when it realized that VoIP was here to stay, the telecom community took steps to develop a standard to enable operators to incorporate VoIP as one of their offerings. The standard-making body of the telecom industry, ITU, released H.323 as the standard for VoIP equipment in 1996. ITU’s goal in developing H.323 was to enable VoIP to inter-operate with the traditional public switched telephone network (PSTN) and its various access technologies. It clearly viewed VoIP from a traditional carrier’s perspective. IETF, on the other hand, had a different view. It saw VoIP from the Internet perspective. Clearly, there was a conflict of both interest as well as approach between ITU and IETF. This directly impacted the deployment of SIP by carriers, who were in any case slow in transiting to a packet platform for telephony. Also, it added to the complexities that most early adopters of VoIP had implemented H.323-based networks.

Not surprising then, that the telecom world has not yet fully recognized SIP. ITU recognition, which symbolizes the thermometer of the telecom world, has come for SIP, but only to the extent of recognizing the utility of SIP in introducing new IP-based voice and multimedia services. For the important role of signaling in VoIP networks, ITU still sticks to the good old H.323 protocol. Thus, the carriers of this world are still fraught to deploy SIP-based VoIP lest they be cut off from the rest of the telecom community, who still faithfully adhere to ITU norms. It is only CLECs who are showing more faith in SIP by straightaway going for deploying SIP-based VoIP or are in the process of transiting from H.323 to SIP. Most aggressive among the new SIP implementers are broadband access providers, like Vonnage of the US, which is using SIP to transform its cable network from an Internet access network to a multimedia network capable of full-scale telephony of the PSTN type and not just PC talk.

Market research agency Infonetics put the market for packet voice equipment at $1.2 billion in the calendar year 2002. And it predicts that the market will grow at a CAGR of 40 percent to reach $4.6 billion by the year 2006. A large portion of this would be media gateways and softswitches, with the rest of the market being made up of media and application servers. Right now, SIP equipment form a small part of most carrier VoIP implementation, deployed as an add-on application server.

However, Venture Development Corporation forecasts that SIP will overtake H.323 as the most extensively used VoIP protocol stack.

Propelled by Enterprises 



Of late, two major trends have been pushing carriers to try out SIP. As in any service, customer is King. And you provide what he wants. In the enterprise arena, SIP has clearly proven itself as the most preferred technology standard, much because of its lightness, simplicity and closeness to popular Internet technologies with which it easily integrates. The enterprise IP telephony market is among the fastest growing telecom market today. Synergy Research values the market to be worth $863 million in calendar year 2002. Over 1 million IP phones were shipped, in addition to LAN telephony equipment and IP PBXs.

And technology-wise, almost every IP phone and IP-PBX available in the market comes not without the support for SIP, if not entirely based on SIP. According to an internal finding by VoIP technology developer Windriver, more than 95 percent of all VoIP products support SIP. And this also reflects on the telecom service providers’ support of SIP, by almost 86 percent of service providers, mostly along with H.323. Major reasons for the sudden recognition of SIP among others, was the major push given by Microsoft, which mandated SIP in its Windows XP and MSN instant messenger, and Cisco Systems, which made SIP a part of its IP phones. 

Another major milestone for SIP has been the recognition by 3GPP, which has chosen SIP over other technologies for integration into the next-generation mobile communication technologies. This was just what the doctor had ordered for SIP.

Already, this has given a momentum to this multimedia signaling standard. Mobile communications is clearly emerging as the preferred mode of personal communications not only in developed countries but in emerging and underdeveloped nations as well. Add SIP-powered seamless multimedia applications like IP voice/video conferencing, instant messaging and gaming to an already SMS/MMS-enabled medium and the much elusive killer mobile applications could be just round the corner.

According to market research agency, Analysys, SIP will disrupt the telecommunication value chain, pushing mobile operators, ISPs and ASPs to take advantage of it. It predicts that SIP-SMS gateways will be in place in 2003, thus boosting ARPU for 2G mobile operators. Europe itself may have 200 million SIP clients by 2007.

Nareshchandra Laishram

SIP DEPLOYERS