Tag Archives: session initiation protocol

Demystifying SIP


The telecom industry has a tendency to shoot itself in the foot. It seems that every time a revolutionary idea emerges, it’s given a technoid sort of name that confuses the general public. SIP is no different.

Everyone knows what an apple is. Not everyone knows that the apple belongs to the subfamily Maloideae of the family Rosaceae. Why? Because no one cares…there’s no practical reason or value in knowing. And besides, who remembers this scientific jargon?

Likewise, everyone knows what a phone call is. Most everyone now knows what the Internet is. Very few people know what SIP is. The fact is the telecom industry, once again, labeled a revolutionary Internet communications capability – SIP – an acronym (no shortage in the industry on these) that describes its technical function, not unlike T-1, MPLS, DTMF, SMDS…the list goes on forever. And once again, the telecom industry has managed to intimidate and confuse the very people who need what it has to offer!

So let’s demystify this SIP thing once and for all. SIP stands for session initiation protocol (bare with me…it gets easier), a signaling protocol used for controlling multimedia over the Internet. More recently it has become associated mostly with the protocol for Internet phone calling that we know as VoIP. SIP enables VoIP calls to be made by most new business phone systems that are connected to the Internet with a high speed facility – DSL, fiber optics, wireless, etc.  A “SIP trunk” refers to the call path from a business phone system over a broadband connection and through the Internet – an alternative way of providing phone calling rather than the standard landline. If a phone system is not SIP-enabled, phone calling is still made possible by placing a protocol converter between the phone system and the Internet connection.

One more thing – why use SIP? There a few major reasons:

  • Cost reduction – The savings over traditional phone lines can be huge!
  • Scalability – Easy to implement, program and use.
  • Universality – It speaks the language of the global Internet.
  • Receptivity – The future of communications will be SIP-driven.

SIP – It’s that simple…well, almost. There are more technical aspects to SIP, but these are the basics. But the fact remains – the concept should have been given a different, more creative name by the telecom industry that everyone understands. Telecom should probably emulate the creativity of, let’s say, the computer industry. After all,  everyone knows what an apple is, thanks to Steve Jobs.

The SIP Surge

SIP trunking continues to steal the headlines in the world of VoIP phone services, but it represents only a fraction of the total business trunks in service today. So why all the hype about SIP?

SIP (session initiation protocol) experienced slowness in its early adoption stage, which is not unusual considering that legacy TDM solutions have been generally reliable and around for a long time. SIP has had to earn its place in the network domains of the small and medium enterprise, and that’s exactly what’s happening! The fact is that despite a sputtering economy, SIP trunking deployments doubled last year, making it one of the best performing VoIP services. And according to industry sources, the SIP trunking market in North America, which closed 2009 at $717.3 million in revenue, is projected to grow to $3.9 billion in revenue by 2016. That represents a seven year surge in growth of 544%!

You may ask, “What’s driving the SIP trunking market?”

It’s already an overly exploited VoIP industry term, but it still holds the promise of SIP – convergence, the ability to bundle voice and data on a high speed Internet facility. With TDM, a PRI or T1 provides up to 23 and 24 channels respectively, which for the large enterprise may still work well, but for the small and medium business, trunk capacity is a cost issue for which SIP trunks provide an economical solution. Simply stated, bundling eliminates phone lines and associated costs. And since SIP trunks can be ordered one at a time and then over-subscribed per number of phone stations, SIP becomes an even more attractive cost saver. Taking it yet another step, for businesses with multiple locations, SIP may be configured as centralized trunking that leverages the Internet cloud for inter-location traffic – another cost benefit.

Finally, SIP is a foundational service of other emerging business VoIP services, such as UC (unified communications). UC represents the latest in integrated IP services like instant messaging, presence information, IP telephony via PC as well as IP phone, video conferencing and speech recognition – all subjects of our future blog posts!