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.