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| Great article: Quote: Should Your Next IP PBX Run on SIP?
Written by Edwin E. Mier
Tuesday, 30 August 2005
Unless you’ve been hiding in a cave in eastern Afghanistan the last few years, you’ve heard of SIP, the Session Initiation Protocol. For signaling and call-control—read VoIP, along with video, Instant Messaging, and so on—SIP is emerging as the way to do real-time communications over the Internet.
But has SIP reached the stature—and stability—for you to consider as the protocol basis for your next IP PBX? That is the question.
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Miercom has been comparatively testing IP PBXs for nearly five years. And starting about two years ago, pure-SIP-based IP PBXs began emerging on the scene, pioneered by Pingtel. Several such systems are available today, and even the “legacy” PBX vendors are getting into the SIP act.
What does this mean for enterprise customers? Here are a few key points to keep in mind:
First, understand how SIP is being rolled out in products. There are several ways that SIP support in IP-enabled PBXs is being implemented:
1. IP PBXs that are purely SIP based. These are relatively new PBX players, whose products were built from scratch for IP telephony, and which tend to be oriented to the small-to-medium-sized (SMB) marketplace. Two such systems we’ve recently tested: Pingtel and Dialexia.
2. Legacy PBX vendors, who have implanted SIP support in their core PBX software engines. The latest versions of Avaya’s Communication Manager, Nortel’s CS 1000, and others, have been “SIP enabled” in this manner. These require an adjunct SIP call controller.
3. Then there’s everybody else, which includes (a) vendors still planning their SIP strategy, (b) vendors who have a SIP plan, but are late bringing it to market, and (c) a few vendors who still don’t know what to do about SIP.
Secondly, appreciate what SIP buys you. Here’s what we’ve seen and confirmed so far:
1. SIP support lets you select from a dozen or more affordable, third-party SIP phones and other SIP endpoint devices. We especially liked the $95 SIP phone from ACT, with all the features of leading vendors’ IP phones for about one-third the cost.
2. SIP lets you also choose the rest of the key components of the IP PBX, like the gateways that connect to the PSTN. In fact, some all-SIP IP-PBX vendors sell you their system as basically software on a CD. Or you can hire the vendor or reseller to assemble all the pieces for you.
3. Support for SIP trunking. It is the way telecom trunking is headed. Instead of traditional, channelized T1s to your local telco, you deliver a SIP-formatted IP bit stream right to your WAN/VoIP carrier—replacing trunks to your distributed locations.
4. Standard, SIP-based support for video, Instant Messaging, and Presence—where dozens of vendors are delivering applications, endpoint devices and subsystems based on SIP.
So why would anybody not want SIP support in their next IP PBX? Well, there are several not-insignificant issues, based on the state of SIP today:
1. SIP-product interoperability, is still far from assured. You won’t see general plug-and-play for a while yet. In the meantime, expect some correctible issues when deploying different vendors’ SIP products.
2. SIP is the bleeding edge of future telecom, and you must be willing to bleed a little. You will need to follow the standard’s evolution, and take responsibility for finding and fixing faults. If you want a single source to blame, then stay away from SIP.
3. Configuration and management are two areas still largely unsettled in SIP standards. In a mixed-vendor, SIP-based deployment, expect a mix of management interfaces and capabilities, that likely won’t play well together.
The optimum solution? Set up a SIP test bed, like you did with VoIP a few years ago. It seems a sure bet SIP will still be here long after you’ve retired.
Ed is a VoIP consultant, author, and founder of Miercom, a product test center in East Windsor, N.J., which specializes in VoIP and IP-telephony product testing. | |
09-05-2005, 11:47 PM 
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