Take a SIP – What is a SIP Trunk Anyway

Open just about any Telecom, Contact Center or Communications trade magazine and you are sure to see an article touting the virtues of SIP Trunking. But what is SIP trunking really and how does it differ from Voice over IP (VoIP)?

SIP is an acronym that stands for Session Initiation Protocol and as the name suggests, it is a protocol that sets up and tears down a voice, instant message or other media’s “session” or instance.  SIP is used hand-in-hand with a VoIP call to begin and end a VoIP call or “session”.

For those of us who have lived in the communications world for several years, we think of a SIP trunk as an IP-based voice T-1 of sorts.  In an environment where a customer contracts with a long distance carrier for a traditional T-1, the carrier is not concerned with the phone system or the phones behind the T-1. The T-1 simply delivers a call across a dedicated facility to the customer’s place of business without knowing or caring about what the phone system does with the call or what brand of phone sits on the user’s desk.

A SIP trunk similarly is not concerned with the devices at the user’s premise or what happens to the call once delivered to the user device so long as the device is able to support the SIP signaling protocol. SIP trunking is used when the carrier and the user both have SIP capable equipment, thus speaking the same technical language in order to pass a phone call from one location to the other.

So if a SIP trunk is kind of like a T-1, then why would you want one and what advantages does a SIP trunk offer over a traditional voice T-1?  Essentially the SIP protocol offers several advantages: flexibility, cost savings, speed to implementation, and integration with other applications.

Unlike a traditional T-1 that is on a separate voice network dedicated to the transmission of voice calls, SIP is a data protocol and when used in conjunction with VoIP, both phone calls and data applications ride the same network and can be converged and integrated with other systems to allow next generation features such as presence  and unified messaging,  key components in Unified Communications ( I’ll save that for another entry).

Additionally, SIP trunking can use existing internet bandwidth so it achieves cost savings and speed to implementation.  Instead of ordering an additional voice T-1 to accommodate a peak calling period and waiting 45 – 60 days for delivery, then being committed to that T-1 for the next 12 to 24 months, SIP trunks can utilize excess internet bandwidth or additional bandwidth can often be added to an existing internet connection within a few days of notifying the ISP.

SIP trunks can also be secured and traverse a private, managed network offering quality of service (QOS) with service level agreements (SLA) should quality and security be a major concern (hopefully both are) vs. the open internet which of course is not owned or managed by any one entity.

Hopefully this gives you a little background information on SIP Trunks. NICE offers SIP trunks as an alternative or supplement to traditional T-1 connections offering virtual dedicated connections between the NICE CXone platform and the customer premise.