VoIP's SIP Explained

This story appears in the October 2005 issue of Entrepreneur. Subscribe »

The analog phone may soon be relegated to the world of 8-tracks and brick-size cell phones. When you look at moving up to VoIP, those old desk clunkers will be the first to go. In their place, you'll get something new, and there's a good chance it will be a SIP phone. SIP stands for Session Initiation Protocol, a signaling protocol that establishes sessions in an IP network. A session may be a simple two-way voice call, or it might be something more advanced, involving conferencing or multimedia. Most important, it's become a hot choice for VoIP systems.

One nice feature of SIP is interoperability. You're not necessarily tied to one vendor. You could install a SIP-based IP PBX from one vendor and SIP phones from another. That's good news for growing businesses that already have an IP-PBX system and are looking to upgrade or expand their stables of desk phones. You have a wide variety of choices, so you can shop for features, voice quality and price.

What's really glamorous about SIP is that all its extra feature potential makes your standard, plain-old-telephone-service phones look like old appliances. We're talking about unified messaging, click-to-call and teleconferencing, among other features. Chances are, you can find one to fit all your business needs.

The Zultys Technologies ZIP 2x2, a $230 (all prices street) upper-midrange phone in their line, features two Ethernet ports, Power over Ethernet and three-way teleconferencing. The phone also sports advanced encryption standard, a good idea for sensitive conversations and for entrepreneurs working in the legal field.

The $280 Cisco 7940G comes stocked with a large display, a built-in headset port and a speakerphone. Cisco aims this particular phone at "transaction type" workers, and it comes with two programmable line and feature keys. In the same price range, the $300 Siemens OptiPoint 410 Standard also comes with PoE, a speakerphone and a built-in LAN switch.

In the budget range, the Grandstream Networks GXP-2000 comes in at a very affordable $110. You still get two Ethernet ports and multiparty conferencing, and you can add PoE with an optional cable kit. The Avaya 4602SW IP Telephone, on the other hand, lands in the middle of our price range at $170, with 12 programmable call appearance/feature keys, two Ethernet ports and a speakerphone. All the major SIP phone manufacturers have a variety of models, with differences coming down to features like display size, ability to customize and number of call appearances.

Other considerations include whether you prefer physical buttons to access most features or don't mind scrolling through a display menu. Voice quality is always a top priority, so look for phones with good jitter-buffer technology. Also, if you have Cisco equipment and want to use PoE, be sure the SIP phones you buy support Cisco's pre-standard proprietary version of PoE.

Other manufacturers to check into include Alcatel, Nortel Networks, Polycom, Snom Technologyand Tiger Netcom. Some IP phone manufacturers are planning to make SIP upgrades to some of their existing phones via a firmware update. Talk to your IT consultant or value-added reseller and fellow business owners for information and recommendations.