SIPping the WAN Fantastic

THE LIGHTS, THE SPARKLE, the high-heeled shoes getting into a new technology is a little like your first high school dance. You arrive, filled with promise and optimism, but by the end of the night, there will be winners and losers those who dance, and those that cant.

When it comes to SIP trunking, channel partners need to get out on the dance floor, lest they end up as wallflowers in what is shaping up to be a spectacular shift in the PRI/T1 tango.

SIP Trunking What is it?

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The general premise for SIP trunking is convergence for a customers WAN, says Steve Lacoff, vice president of product management and marketing at SIP trunking provider Inc. A channel partner may have put in an IP PBX and converged data and voice onto the customers LAN for internal communications. But how do you access the PSTN; the outside world? SIP trunking simplifies the answer to that question.

Essentially, SIP trunking allows businesses to eliminate PRIs, T1s and local charges, replacing them with a single pipe to the Internet, which terminates directly to the IP PBX on the customer premise. Using VoIP, customer traffic is routed via that connection to a company like, BandTel LLC or others, which takes care of terminating the traffic, aggregating a stable of underlying providers.

Fundamentally, its the VoIP cost savings of as much as 50 percent over TDM charges, says Lacoff. Thats an easy thing for a VAR to demonstrate from an ROI perspective. But there are other advantages.

For instance, SIP trunking eliminates the equipment previously needed to convert traffic from the IP PBX to the PSTN circuits. SIP trunking requires no hardware; VARs simply point the IP PBX toward the broadband pipe and the trunking providers IP address. Most IP PBX vendors have built SIP trunking support into their boxes; many are certified as interoperable with certain SIP trunking providers., a service provider, and Mitel Networks Corp., a PBX maker, for instance, have such a partnership.

While SIP trunking takes away complexity, it also allows easier scalability. In the TDM world, to scale you buy PRIs in 23-channel increments, theres a provisioning interval and a truck roll involved, says Lacoff. With SIP trunking, its a matter of provisioning enough bandwidth on your broadband pipe, and simply adding new numbers. It can be up in a couple of days, without a truck roll.

Thats because the nature of SIP trunking is virtual; a SIP trunk is simply a concurrent call or packet stream, and it has no relation to physical channels. This fact also makes for easier WAN design. If Im in a business with local calling needs, like a bank, I need a loop for each branch in the traditional world, says Lacoff. Its impossible to consolidate all the local channels in one location. But you can have SIP trunks terminate at the headquarters, and feed four-digit extensions out to everyone.

SIP trunking also supports number portability, standard calling features, 911, 411 and other functionalities, in case a customer asks. It is like-for-like on that side of things, says Chris Dunk, CEO of BandTel. In fact, you get a little more with some advanced calling features like findme/ follow-me.

SIP trunking may provide benefits and be a convenient add-on or follow-on to an IP PBX sale, but VARs should be aware of the customer questions they likely will face. For one, does it work and does it have QoS? We offer redundancy from a carrier perspective, says Dunk. Everyone has a bad day now and then, but we dynamically route traffic accordingly, and offer a 100-percent money-back SLA to back up our service.

SIP trunking providers often have a certification process to stress-test its system and the customers IP PBX to further allay any QoS fears.

Also, there is work for a VAR to do to become fluent with proposing the solution. He should know what to ask the customer, such as how many people will be using it and what sort of codec is in use on the IP PBX, says Dunk, noting this query determines the number of concurrent calls and the amount of bandwidth must be provisioned. Customers like to oversubscribe by ordering five concurrent calls for 10 people but you have to ask, how many of those users are making mission-critical calls?

While residual commissions are the standard channel partner compensation model in the space, pricing structures vary widely by provider. That may make it difficult to present a customer with two or three side-by-side options or to figure out commissions. sells SIP trunking at $20 per month per trunk, which comes with one phone number. “The company can reduce the rate to as low as $10 per month with a three-year plan.” Additional phone numbers are sold in packs of 10, 20 or 100, ranging from $7.50 per month to $50 per month. So, if a company wants to enable five concurrent calling lines to be spread across 15 people, a VAR or agent would sell five trunks and a pack of 10 additional numbers. It also offers a perminute pricing plan.

BandTel, on the other hand, offers perminute plans as well as a 1,500-minute plan for $39.95 per month.

Also, sales partners need to know how to troubleshoot SIP and explain the protocol to internal CIOs if necessary. And if theres video or other applications in play, one needs to know how to appropriately size the pipe and configure the IP PBX, says Dunk. We consider 2007 the year of educating the VAR on this.

This year also may be the year of SIP trunking in general. The technology has been around, but all of the sudden its really catching on, says Laith Zalzalah, director of business development for carriers and hosted services at Mitel. Its the wave of the future. And all VARs have to do to sell it is call and order up another license. Thats it no physical infrastructure to worry about.

SIP Trunking Step by Step

SIP trunking is a virtual voice trunking solution out to the PSTN that provides inbound and outbound local calling, domestic and international long-distance, and toll-free numbers to a premise via a connection to the Internet. It requires no physical channel and is handled at the IP layer using a standard VoIP protocol known as SIP short for Session Initiation Protocol.

SIP is the real-time signaling protocol for VoIP, used for Internet conferencing, telephony, presence and events notification (emergency calling). In recent years, SIP has been expanded to support video and instant-messaging applications.

SIP uses a text-based programming language designed to perform basic call-control tasks, such as session call setup and tear down, and signaling for features such as call hold, caller ID, conferencing and call transferring. This means that, like programming templates in Microsoft Office, there are scripts for programming SIP communications features. VARs can add tremendous value by learning how to do this to customize the applications running on the LAN/WAN.

See TECHtionarys multimedia introduction to SIP trunking at sip-it-main.swf. The tutorial covers, among other things:

  • Integration of new hosted VoIP solutions.
  • Integration of VoIP with IP PBX.
  • Migration to VoIP with older TDM PBX systems.
  • IAD support for analog telephones and hybrid IP/analog telephones.
BandTel LLC Inc.
Mitel Networks Corp.

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