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The Standards StruggleWill SIP be a Drain on H.323's Momentum?By Paula Bernier While the Internet protocol (IP) telephony industry talks about its support and continued development of standards, and new "H.323-compliant" equipment has begun to arrive, the fact remains that true interoperability among different vendors' H.323 gateways is lacking. "Although later this year all the gateway vendors will come out with gateways in boxes labeled H.323, they still won't talk to each other," says Tom Evslin, chair and CEO of ITXC Corp. (www.itxc.com), an Internet telephony settlements and services provider. "They won't talk in H.323." Still, the widespread adoption of a standard for Internet telephony at this early date in the industry's life is considered a significant achievement. And, as the many other standards that have come before (the public switched telephone network's synchronous optical network (SONET) standard is a key example), it will take some time for vendors to agree on exactly how to implement the H.323 standard to achieve true interoperability. But just when H.323 appeared to be on the road to widespread interoperability, a new implementation option for Internet telephony has emerged. MCI Telecommunications Corp.(www.mci.com) and several vendors are now saying that SIP, or session initiation protocol, is better suited than H.323 for wide area Internet telephony. Expanding to the WANH.323 started life as a standard for video over local area networks (LANs). It established a standard way for videoconferencing equipment and software from different vendors to talk to each other. Whereas early videoconferencing systems from companies such as PictureTel Corp. (www.picturetel.com) would only communicate with other PictureTel systems, H.323 enables the millions of users of NetMeeting from Microsoft Corp. (www.microsoft.com), Internet Videophone from Intel Corp. (www.intel.com), CU-SeeMe from White Pine Software Inc. (www.wpine.com) or any other standards-based client to participate in multipoint group conferences, explains White Pines spokesman Forrest Milkowski. Earlier this year, H.323 expanded. Version 2 of the standard addressing select wide area networking issues was approved by the International Telecommunications Union (ITU) in February. Among other things, Version 2 sets up a security framework for voice over the Internet (it doesn't mandate what kind of security, but instead gives a framework for encryption and authentication); and lays out basic responsibilities of the gatekeeper, which is the network management element of H.323 that manages bandwidth and dialing plans as well as handles other control issues relating to enhanced services, explains Scott Petrack, principal technologist at VocalTec Communications Ltd. (www.vocaltec.com). And early work on Version 3 of H.323, which Petrack says won't be decided on for another two years, already has begun. Version 3 probably will address supporting fax transactions over IP links. Other issues that remain to be addressed include how individuals can find each other on the IP telephony network; how IP telephony names or numbers should be assigned; and how to fine-tune issues related to DTMF (dual tone multifrequency), says Petrack. The Trouble with H.323Despite the expansion of H.323 to address wide area networking, the standard still has significant shortcomings that has some wondering why the Internet telephony industry went down the H.323 path to begin with. "We latched on to a standard that wasn't what we wanted it to be originally," says Joel Hughes, director of IP telephony for Natural MicroSystems (www.nmss.com), which--like many vendors in the industry--supports H.323. "From a technical standpoint, I've been less than pleased with H.323." The primary shortcomings of H.323 as compared to SIP relate to call set-up, simplicity and scalability. "H.323 is pretty nasty," according to one vendor who asked not to be named. "It's too complex, and has long call set up times--20 to 30 seconds." SIP, by comparison, takes four packets for call setup; H.323, in contrast, uses about three times the number of packets to set up a call, says the vendor. SIP also allows additional callers to be added on an Internet telephony call when it's in progress, adds Alistair Woodman, product line manager of packet voice technologies for Cisco Systems Inc. (www.cisco.com). What SIP offers that H.323 does not is generality and simplicity, explains Hennig Schulzrinne, associate professor for the department of computer science at Columbia University (www.cs.columbia.edu/~hgs/sip), who was the only speaker talking about SIP at last year's Voice on the Net show in Boston and who led a panel on the issue at VON this spring. "We want a simple, general protocol that can evolve without requiring you to run Windows 95 or NT on your phone," Schulzrinne says. Today the industry really doesn't understand all the features it wants to offer with Internet telephony in the future, Schulzrinne adds. SIP allows new features to be added easily because the feature is "self describing" using the existing feature and functionality building blocks within SIP. Put another way, SIP's information element is completely scaleable and can take on new forms, while H.323 "crammed the whole protocol into one information element," says the vendor who asked not to be named. Kerry Hawkins, vice president of sales and marketing at Vienna Systems Corp. (www.viennasys.com), adds that because SIP is packet-based--rather than connection-oriented as is Q.931 used in H.323--it also can carry more information associated with a call. For example, a user could upload information to forward calls to an alternative number at certain times, or a carrier could add an authorization number to a call if the gateway where the call terminates is owned by a different carrier, he says. The Net-Head Way"SIP is more of an Internet protocol. It's the net-head way of thinking," says Henry Sinnreich, senior engineer in MCI's Internet Engineering Organization. "H.323 has buried in it all complexity of ISDN [integrated services digital network] signaling, OSI [open systems interconnection] messaging, ASN.1 encoding and, worst of all, it uses TMN [telecommunications management network]. Obviously, none of these fit into the Internet--it's a square peg in a round hole," he says. Sinnreich says that X.400 messaging, X.500 directories and OSI all were failed attempts to replace Internet technologies for commercial reasons. "It has been proven that the simplicity and the thoroughness of the Internet prevails," he says. What's more, he says, it doesn't make sense to use a standard from the $60 million conferencing industry for multibillion-dollar industries such as telecommunications and the IP networks. "The conferencing industry has not had very profitable companies, so there is very little reason for the telecom industry or the Internet to bend over backwards to be dominated by a third industry's architecture," he says. Some, like Sinnreich, hope SIP will slowly overtake H.323. "SIP for telephony is a young technology, so we have to give it a chance to grow," says Sinnreich, adding it won't be integrated into H.323. Others believe the two technologies can peacefully coexist. Hawkins of Vienna says carriers might want to use SIP internally and H.323 where they need to interoperate with other vendors' gateways. "There's no reason not to implement both [H.323 and SIP] because once you implement H.323, SIP is like a walk in the park," Schulzrinne says. Meanwhile, some such as Jeff Ford, chief technology officer of Inter-Tel Inc.(www.inter-tel.com), see SIP as a blip on the Internet telephony radar screen. "[SIP] is an alternative to H.323, but I think it's going to lose because MCI is the only backer," says Ford. "H.323 definitely has the mind space as far as the Internet telephony service providers (ITSPs) [are concerned]." Of course, ITSPs don't want to be locked into using a single vendor for their gateways and gatekeepers, and are looking forward to the interoperability that the widespread support for H.323 promises. Some have even suggested that SIP is an attempt by MCI--which of course may see Internet telephony as a threat to its core circuit-switched long distance business--to derail the Internet telephony industry. Whatever the case, Michael Cassin, voice product manager at carrier Concentric Network Corp. (www.concentric.net) wishes SIP would just go away. There always will be better or worse options that turn up after a standard is adopted, he says, and the industry has to decide to move forward at some point. "I'm totally focused on H.323," he says. "I just want the pain to end." Copyright © 1998 by Virgo Publishing, Inc. |
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