Wireless Propagator: VeriSign Verifies Dual-mode Voice

More commonly known to enterprises for its digital certificate services, VeriSignrecently announced trials of the company's Wireless IP Connect Service. VeriSignnoted the involvement of three major universities at which users will have asingle mobile device that roams between Wi-Fi and cellular networks. Thecompany is also a member of mobileIGNITE, a network convergence industrybody led by BridgePort Networks.

In an interview with Tom Kershaw, VeriSign Communication Services' vicepresident of Next Generation Services, he says VeriSign is "all about connectingdifferent VoIP islands." Currently, there is no VoIP peering point thatinterconnects Vonage with SIPphone, Packet8, FreeWorldDialup, etc. Emblematicof FMC (fixed-mobile convergence), VeriSign plans to bridge VoIP, cellular andtraditional voice. Touting its existing roaming and settlement agreements withcarriers as well as its current SS7 (Signaling System 7) connections to allmajor carriers, VeriSign will operate a gateway that connects external VoIPmedia and signaling flows to the appropriate mobile or fixed voice carrier.

Kershaw casts some necessary doubt on the PBX-centric model demonstratedin the Motorola/Avaya/Proxim solution. This trio, which initiated the SCCANforum, splits the functionality among handset, PBX and WLAN gateway,respectively. What's unique is that the PBX needs to have an SS7 link to thewireless carrier so that location registration and call control can be handled.Not many PBXes have such interfaces, and carriers are uncomfortable inopening up their SS7 networks to enterprises and university campuses alike.

Mobile carriers are partial to UMA (Unlicensed Mobile Access, now transferredto 3GPP) because it essentially allows a cheaper (and perhaps organization-supported) pico-cell, by way of a wireless network, to connect to their existingGSM networks. A secure tunnel is built over the wireless IP link, which registersthe handset onto the carrier's network. UMA is not based on SIP, and to thatextent excludes the solution from interfacing directly with existing enterpriseVoIP networks. On the flip side, there is some significant momentum with thistechnology. Nokia recently committed to using UMA in its infrastructureequipment, and there are already several handsets in the works, with Motorolaparticipating, too.

The VeriSign model takes a more carrier-agnostic approach. Enterprise VoIPtraffic terminates on VeriSign's hosted gateway, distinctively named "Wi-FiMobile Gateway" (WMG), and performs the necessary SIP to GSM/CDMA inter-working. Besides the necessary signaling and enhanced service delivery, it alsoupdates the native mobile carrier's database with the network location of thehandset. Owing to its existing relationships with major carriers, VeriSign canalmost immediately provide transparent and equal access to all mobile carrierswithout either a forklift PBX upgrade or requiring an organization to limit itscellular relationship to just one provider.Because mobile carriers are essentially extending their cellular networks tothird-party Wi-Fi networks, they are naturally concerned about quality, reliabilityand service levels. VeriSign's Kershaw confirms what Motorola executivesremarked in an earlier briefing: Mobile carriers want assurances that theorganization's Wi-Fi network has the necessary QoS, seamless and ubiquitouscoverage, reliability and optimized operation between handheld device andaccess point. Carriers' other concerns include feature parity between Wi-Fi andcellular networks and handset functionality. SIP, as defined and expanded inmultiple IETF (Internet Engineering Task Force) RFCs, lacks some of the extrafeatures needed for specific implementations of FMC. Appreciably, SIP isextensible and, hopefully, that functionality will be rolled into future standards-body work.

The three universities participating in VeriSign's trial--University of Michigan,Northwestern University and Texas A&M University--are using faculty andstudents as guinea pigs, with the number of users across all the trialsnumbering just over a hundred. Similar to what was rumored with theTalkTelecom deployment in Ireland, this pilot does not use traditional candy-baror flip-phone handsets; rather, it is based on PDA-style HP iPaqs that includeGSM and 802.11b support. According to Kershaw, mobile voice usage in theuniversity setting, encompassing college dorms, classrooms and faculty offices,is about 60 to 70 percent of the subscriber's total airtime. This is much higherthan the oft-quoted average of 30 to 40 percent in the enterprise space, and itwas a contributing factor in selecting higher education as a place to initiatethese trials. Because some schools have comprehensively deployed theirwireless LANs across their campuses, it might well be possible for students tospend almost their entire day within proximity of a Wi-Fi access point.

Progress is definitely being made on the wireless convergence front. Althoughthe market is very young and the supporting technology awkward andimmature, different approaches to convergence are being worked out. TheMotorola/Avaya/Proxim partnership has the advantage of a well-tested andfeature-rich solution with a custom handset that's more acceptable than thebulky PDA used in the VeriSign trials. Proxim and Motorola have also tweakedtheir respective parts so that roaming between Wi-Fi actually works withinacceptable tolerances. But replacing your existing PBX with one by Avaya (or, inthe future, with Cisco's CallManager) is not a lighthearted task. VeriSign doeswell by demonstrating an alternative dual-mode solution. Time will tell how thesecompeting, and sometimes complementing, concepts fair in the marketplace.