• United States

Users hoping SIP’s the answer

Oct 21, 20027 mins
Cisco SystemsNetworkingVoIP

But concerns remain over whether VoIP products will work together.

John Ridley is stuck between the old world of circuit-switched telephony and the new world of voice over IP. How soon the Coca-Cola network executive can move forward depends largely on which IP telephony standards key vendors support and how true they stay to those standards.

John Ridley is stuck between the old world of circuit-switched telephony and the new world of voice over IP.

How soon the Coca-Cola network executive can move forward depends largely on which IP telephony standards key vendors support and how true they stay to those standards.

Ridley, who is looking to replace a loosely connected collection of old PBXs, is among a growing legion of network executives who say products based on Session Initiation Protocol (SIP) are the best bet for delivering the true benefits of VoIP. Such gear could help simplify network management and support new applications, they say, although only if the products boast Ethernet-like interoperability.

Providers split on SIP, H.323Report from the Next Generation Networks conference.Quality question remains for VoIPPart 1 of this seriesIs this a do-it-yourself project?Part 2 of this seriesAnswers to your VoIP questionsPart 4 of this series

“The problem with IP telephony equipment today is that there is no [interoperability] among vendors,” says Ridley, whose converged network would serve 70,000 employees.

Network executives are wary that vendors will repeat the mistakes they made with the older, less-functional H.323 technology. While H.323 has been implemented widely, vendors took so many liberties with it that getting their products to work together can been difficult.

“There are a lot of slacker customers out there like us who are just sitting on our old legacy stuff, waiting for the market to evolve,” Ridley says.

Making the case for SIP

Work on SIP, now an IETF standard, started in 1995. It was designed to run on IP and supports a plethora of communications technologies from voice to instant messaging to video. SIP also lets users establish presence at different locations on a network, saying “I am here” and letting everyone or just a select group know it. SIP promises to support new services such as click-to-dial phone calling, interactive voice response navigation of Web sites and conferences that are set up when all participants are ready.

SIP is considered more efficient than H.323, which is commonly criticized as being too chatty, sending lots of messages over the network and creating potential congestion if VoIP is heavily used. Critics of H.323 say the overarching standard for interaction among a set of other standards is too unwieldy to customize.

Enthusiasm for SIP has been on the rise in recent years because of work done by organizations such as the SIP Forum, which now has 27 member companies including Cisco, Lucent and Nortel. Microsoft last year gave SIP a boost when it replaced H.323 with SIP in its Windows Messenger application, which supercedes Windows NetMeeting from the days of Windows 95/98.

SIP “bake-off” tests performed by Network World and by industry groups such as the SIP Forum also have helped build hope among network executives that SIP products would work together once released.

A survey of 96 vendors last year by Network World and Miercom showed 73% had H.323 products, while only 40% had SIP gear. However, 51% said they planned to implement SIP on their products over the next year.

Nortel and Siemens are among the vendors pushing SIP. Nortel says it will ship its Succession Communication Server for Enterprise Multimedia Xchange (CSE MX) in December. Siemens, which already has SIP-capable phones, says its HiPath IP PBX software will support a SIP stack along with its core H.323 code in the next major revision, which is expected in the first quarter of next year. Alcatel has said its OmniPCX IP PBX gear also will be “SIP-capable” by next year.

Others, such as 3Com, which uses a proprietary version of H.323 for call control on its NBX IP telephony server, and Avaya are less enthusiastic. Avaya, third in IP telephony sales, says its line of ECLIPS IP telephony equipment can be enabled with SIP or H.323, but the company’s proprietary H.323-based protocol is still the default.

H.323 vs. SIP

While both H.323 and Session Initiation Protocol (SIP) can support VoIP, the protocols have plenty of differences.
H.323 SIP

ITU standard

IETF standard
Designed on models of ISDN and ATM signaling

Designed for use

of the Internet
Older and more established, particularly in LANs Newer standard
Complex, using both binary encoding and abstract syntax notation

Relatively simple,

text based; similar

Difficult to customize Accessible to customization

And then there’s VoIP market leader Cisco. The company supports SIP across its gateways, routers and some IP phones, and it says the protocol will be added into its CallManager enterprise IP PBX. But observers have questioned the company’s reliance on proprietary protocols and whether that would interfere with the interoperability of SIP-enabled gear from Cisco and others.

“Cisco’s voice solutions contain a number of proprietary and prestandard aspects,” according to a recent report by Gartner Vice President Mark Fabbi. “Although Cisco supports SIP . . . in a number of products, its integrated solution requires that users implement its proprietary ‘Skinny’ protocol,” or Skinny Call Control Protocol.

The vendor’s primary call-control technology for its corporate IP telephony products remains proprietary, Fabbi writes. (Cisco also licenses its Skinny protocol to other vendors, such as Polycom). He adds that “nearly all” vendors use proprietary hooks in their VoIP gear that prevents companies’ products from working well together.

“Most vendors don’t want to be interoperable,” says Brian Strachman, a senior analyst with Cahners In-stat/MDR. “No one wants to say, ‘Go ahead and buy our IP PBX phone system, and oh, you can use Cisco or 3Com phones with it too.’ “

The result, Strachman says, would be increased competition, which would force vendors to reduce prices and suffer lower profit margins.

“The [traditional] telecom mindset,” has crept into the IP telephony world, he says, but he adds “it’s been changing. Eventually it will be more open.”

H.323, here and now

While many observers consider SIP to be the future of VoIP, we live in an H.323 world.

H.323 is still used widely on ViDENet, a multivendor IP voice and video network started in 1995, that connects more than 70 universities, research institutions and corporate networks via the Internet and Internet 2.

More than 500 gatekeepers and gateways, IP phones and video stations based on H.323, from vendors such as Cisco, Polycom and RadVision, are deployed. Each member institution is registered in a central directory, which lets H.323 voice or video sessions be set up easily.

“The reason for our widespread adoption of H.323 was that at the time, it was the protocol that proved to work with off-the-shelf components,” says Jill Gemmill, who was ViDENet chair until September, and is assistant director of academic computing at the University of Alabama Birmingham.

Petroleum company Schlumberger chose H.323 over SIP for the same reason.

“SIP was pretty new when we first started looking into [our VoIP] project,” says Brian Spolnicki, an information solutions technical lead at the company’s Houston office. The company recently installed an IP-enabled PBX with H.323 VoIP in a call center to consolidate technical assistance into three call centers in Houston; Calgary, Alberta; and Caracas, Venezuela.

The centers, which support about 60 agents, are connected via T-1 lines and Schlumberger’s DeXa.NET, a private OC-48 WAN. An Ericsson PBX with an IP card sits in Houston and supports call agents using Ericsson H.323-based IP phones in the Canadian and Venezuelan offices.

Spolnicki says he is comfortable with swapping out phones for any other commodity H.323 phone, or a Windows PC with the H.323-based NetMeeting program, if necessary.

“SIP may be involved in other segments of the company in the future,” Spolnicki says, but “it didn’t fit for this particular project at the time.”

Next week, we run through a list of the most pressing questions for a company considering the VoIP leap.