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Wireless Propagator: VeriSign Verifies Dual-mode Voice

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

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

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

Mobile carriers are partial to UMA (Unlicensed Mobile Access, now transferred
to 3GPP) because it essentially allows a cheaper (and perhaps organization-
supported) pico-cell, by way of a wireless network, to connect to their existing
GSM networks. A secure tunnel is built over the wireless IP link, which registers
the handset onto the carrier's network. UMA is not based on SIP, and to that
extent excludes the solution from interfacing directly with existing enterprise
VoIP networks. On the flip side, there is some significant momentum with this
technology. Nokia recently committed to using UMA in its infrastructure
equipment, and there are already several handsets in the works, with Motorola
participating, too.

The VeriSign model takes a more carrier-agnostic approach. Enterprise VoIP
traffic terminates on VeriSign's hosted gateway, distinctively named "Wi-Fi
Mobile Gateway" (WMG), and performs the necessary SIP to GSM/CDMA inter-
working. Besides the necessary signaling and enhanced service delivery, it also
updates the native mobile carrier's database with the network location of the
handset. Owing to its existing relationships with major carriers, VeriSign can
almost immediately provide transparent and equal access to all mobile carriers
without either a forklift PBX upgrade or requiring an organization to limit its
cellular relationship to just one provider.

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