VOICE 2001 Pr otocol War s Th r eaten VOIP Future Larry Hettick Instead of fighting over SIP and At WorldCom, distinguished engineering H.323, vendors should member Dr. Henry Sinnreich couldn’t disagree more. “H.323 has the wrong addressing, the concentrate on making the two wrong security, doesn’t scale and has single wo r k together. points of failure,” he said. “It is extremely complex and has a heavy footprint. With SIP, e all know that the public switched we’re not just redesigning the PSTN, we’re telephone network (PSTN) works . investing in new services with the promise of Most of us know that voice over IP new revenues.” W (VOIP) works. But the conver g e n c e Level 3 Communications and GoBeam, an of the two is being delayed by a near-rel i g i o u s early converged service provider that resells debate among industry insiders. Level 3 VOIP services, also weigh in for SIP. At the heart of the controversy is an either/or “H.323 is the PSTN, and SIP is the PSTN choice between the H.323 and SIP prot o c o l s . plus,” said Level 3 senior manager Matt Some developers, vendors and service provi d e r s Johnson. ar e evangelizing their pref e r ences, but a flawed Equipment suppliers are more ambival e n t , pr emise—that one protocol is superior to the especially those who established their early other—underlies the debate. In fact, both VOIP business with H.323 gateways. Tod a y , st a n d a r ds bring positive elements to the table, vendors like Cisco, Clarent, Commworks and and work is getting under way to make sure that Radvision support both H.323 and SIP. both will operate in the networks of the future. Acc o r ding to Michelle Blank, marketing VP Fighting protocol wars at this stage of the at Radvision, H.323’s capabilities allow carriers game does nothing for either the H.323 or the to make money today. “If you ’re a large servi c e SIP factions, and it casts doubt and uncerta i n t y pr ovider with a need for hundreds of over customer perceptions of VOIP and thousands of VOIP ports today, you must use co n v erged services. In a market with billions of H.323,” added Ofer Sha p i r o, Radvision senior dollars at stake, equipment suppliers and vice president for business devel o p m e n t . se r vice providers should be doing all they can to At Commworks, Houman Mod a r r es, fully integrate both of these protocols, and to di r ector for IP telephony, claims that the traffic educate customers about the efficiency and new mix users send across his company’s equipment se r vices that converged PSTN/VOIP networks is split about 50/50 between H.323 and SIP, but can offer. he acknowledges that the company is “ver y high on SIP, because a majority of our servi c e Who’s Pushing What? pr ovider customers are beginning to deploy it.” The battle between Session Initiation Protocol By comparison, Cisco is “strategically agnostic” (SIP) and H.323 has been brewing for several rel a t i v e to the protocols, said Alec Hen d e r s o n , years now. While SIP has been gaining ground VOIP product marketing manager to servi c e since the IETF standardized it in 1999, H.323 pr ovi d e r s — “ although our customers rarely are. ” La r ry Hettick is vice systems, which were introduced in 1996, are pre s i d e n t , co n s u l t i n g more widely deployed (see “Protocol Primer: Why Choose Sides? with Tel e C h o i c e H.323, SIP and Megaco/H.248,” p. 65 and Ser vice providers have good reasons to select (w w w. t e l e ch o i c e. c o m ) , also “Too Many VOIP Standards,” in BCR, either H.323 or SIP. The early VOIP adopters a consulting fir m that June 2000, pp. 64–69). used H.323 gateways to bypass traditional cat a ly z es cha n g e in AT&T chose H.323 because it was the most ci r cuit-switched paths and offer inexpensive te l e c o m mu n i c at i o n s mature protocol, according to Ann Machi, international long-distance service. Mor e business and product manager for VOIP. “It does what we rec e n t l y , domestic providers have shown interes t ma r keting strate gie s . want to do for our retail and wholesale in VOI P , but they prefer SIP as a platform for He can be rea c hed at customers,” she said, “especially for legacy ne w services, such as unified messaging, click to lh e t t i ck @ integration with our existing network and the talk and others. As for the incumbent local te l e ch o i c e. c o m . customer premises equipment at the edge.” ex change carriers, their lack of interest in VOI P 64 BCR’s VOICE 2001 / SEPT2001 VOICE 2001 is understandable: toll bypass efficiencies are not incumbents like Nor tel and Avaya have chosen im p o r tant in the local exchange, and new to “IP-enable” their installed base of PBXs with VOIP-enabled services are not important in a H.323 transmission gateways, and left the monopoly environment. traditional call control and feature sets in place. Carriers can’t As a practical matter, service providers can’t For these vendors, SIP remains a future option. af f o r d to fully equip their networks with gear for Newer PBX vendors, like Sho r eline Commu- fully equip their both VOIP protocols. They can successfully nications and Cisco, who lack an installed base to networks with mo ve from one technology base to another, as upgrade, seem more focused on SIP. “While we many did who started with analog cellular st a r ted with a prop r i e t a r y software load we call both protocols ne t w o r ks and then moved to digital, but the ‘sk i n n y ,’ we have since included SIP, a SIP call transition can be slow, complicated and costly. agent and MGCP software,” said Hank Lambert, Equipment suppliers, who want to sell those Ci s c o ’s enterprise VOIP marketing direc t o r . upgrades and alternatives, have ever y reason to “I n our arch i t e c t u r e,” Lambert continued, “a remain agnostic. And since both SIP and H.323 call agent like Cisco’s Call Manager can provi d e ar e used today in different service provider ‘sk i n n y ,’ SIP or MGCP as needed by the ne t w o r ks, vendors who want to sell VOI P ne t w o r k, and can include updates as differen t equipment will simply have to support both. st a n d a r ds are needed. The Call Manager can act The major exception to that rule is as a proxy to translate between multiple traditional PBX vendors, who have an easier st a n d a r ds as these standards evol v e. H.323 is st r a t e g y . Their core business value comes from possible, but we haven ’t had sufficient demand the feature set their PBX makes possible. Hen c e , to include it as an option.” Pr otocol Primer: H.323, SIP and Megaco he amount of traffic carried by IP-encapsulated using HTTP, which increases the pool of development “protocols” has now eclipsed the amount of circuit- resources. T based voice traffic by nearly two-to-one, according to “SIP was designed by those who were big believers in Vertical Systems Group. In the 10 years since this shift was the Internet and Internet technologies,” explained Radvi- projected, PSTN network experts have been looking for sion’s Shapiro. “Their first concern was to bring voice over ways to converge the PSTN with packet-based networks the Internet, and then enhance for value-added features like like the Internet. multimedia.” The first such design emerged from the ITU-T’s efforts Houman Modarres of CommWorks agrees. “The SIP to standardize videoconferencing in 1996. It was H.323, model follows the Internet model for creativity. It is open entitled “Visual Telephone Systems and Equipment for and lightweight—a model that is created for adding fea- Local Area Networks that Do Not Provide Guaranteed tures and applications in an open architecture.” Quality of Service.” Subsequent additions, spurred by the Like H.323, the SIP architecture also contains four fast-developing Internet, moved to include standards for main elements, but they don’t exactly map one-for-one to packet telephony and wide area networks in the H.323 the H.323 architecture. They include: family. n User Agent, an endpoint that communicates either as a “H.323 was originally created for multimedia, and then peer or in a client/server relationship with other agents. enhanced for voice” noted Radvision’s Ofer Shapiro. “The n Proxy Server, which makes requests for User Agents. enhancements—features like call hold, call transfer, call n Redirect Server, which closely corresponds to the role waiting—were driven by traditional telephone philosophy.