Section 16.5. VoIP Service Providers
16.5. VoIP Service ProvidersService providers sell dial-tone or call-origination applications, bulk voice trunking, or wholesale interexchange signaling. Some provide all three. 16.5.1. Dial-Tone and Call OriginationCompanies that offer dial-tone service or call origination are often called telephone service providers. Next -generation TSPs are using broadband Internet links to replace the services ordinarily provided by the regional Bell operating companies like SBC, BellSouth, and Verizonservices like simple local and long-distance calling. The essential broadband TSP offers an IP-based trunk, usually using SIP, to connect a single line appearance to its network operations center (NOC), where calls are originated to, and received from, the PSTN. The NOC acts as a CO for the customer, who usually has a VoIP gateway device to connect his analog phones to the calling service. A broadband Internet links the customer's network to the TSP's. This VoIP gateway device is either an ATA or a more elaborate VoIP server. ATAs are used to support analog phones, while, less frequently, embedded VoIP servers may be used to support IP phones. Overwhelmingly, SIP is the endpoint signaling protocol used between the VoIP gateway and the NOC. Some smaller TSPs have begun using the IAX protocol, due to its immunity to problems traditionally imposed by NAT firewalls. The customer provisioning model for each TSP varies slightly. Some TSPs charge a fee for the gateway device and rebate it after a few months' paid use of the service. Other TSPs give the ATAs away free, but demand them back if you cancel prematurely. Still others allow you to bring your own VoIP gateway or ATA. Some even let you use a full-blown softPBX as your SIP client, which, in essence, transforms the SIP link to the TSP into a PBX dial-tone trunk. TSPs in this vein include those listed in Table 16-1. Table 16-1. Independent VoIP telephone service providers (TSPs)
A variation on the broadband TSP formula is to use PC-based call origination instead of hardphones and VoIP gateways. Skype uses such a model, allowing its users to place all calls, even those bound for the PSTN, from its proprietary desktop messaging application. Most TSPs that support hardphone calling offer some kind of softphone solution for PC-based calling, though Skype is unique in requiring it. 16.5.1.1 Bulk trunk providersBulk trunk providers offer business-grade subscribers with dial-tone service en masse. This type of service is intended to replace high-density legacy technologies such as T1 and PRI with a high-density packet-based interface into the PSTN that serves a large group of endpoints in a single office. The use of these VoIP trunks were described in Chapter 13. Bulk trunk providers may or may not place a VoIP gateway on the customer premises. This depends largely on what technology is used to provide the link to the provider's NOCATM, IP, and so on. Whether the customer premises equipment is a VoIP gateway or just a group of IP phones connected by an Ethernet segment, the trunk provider dictates the trunk signaling standards used. Most are presently using SCCP, MGCP, or SIP, A VoIP-compatible bulk trunk service is available from most large network carriers, including Covad, AT&T, BellSouth, MCI, SBC, ICG, and Verizon, and by metropolitan carriers like N2Net (http://www.n2net.net). 16.5.1.2 Wholesale IXCsTraditionally, interexchange carriers have formed a backbone that connects long-distance networks around the world. IXCs dealt in voice bandwidth at the wholesale level, and phone companies tapped into IXC networks using SS7. This kept carrier-grade connectivity relegated to the elite, large operators who had industrial-class SS7 switches. But more recently, a few IXC networks have opened their doors to next-generation VoIP operators. In fact, a majority of VoIP traffic on the Internet today is being signaled and hauled by a few IXCs that specialize in servicing next-generation VoIP TSPs like Vonage. Level3 Communications, Verisign, Global Crossing , and Transaction Network Services have launched services that allow SIP-based last-mile providers and other VoIP TSPs to access facilities on the big IXC, ILEC, and LD networks. This could, for example, allow a startup TSP to gain DID phone numbers and PRI circuits in very faraway places, allowing them to better compete with the already-established incumbent LECs. More information is available from http://www.level3.net, http://www.verisign.com, http://www.globalcrossing.com, and http://www.tnsi.com. 16.5.1.3 Hosted PBXA number of TSPs can host a softPBX at their data center, allowing many small organizations to share a single VoIP server. The subscriber's PSTN connect point is at the TSP rather than its own premises. This makes sense for those who want to avoid the expense of hosting VoIP services in-house. But it doesn't make sense for everybody. If you've got fewer than a dozen users, it might be better to stick with VoIP trunks and a cheap PBX, which costs only a few thousand dollars. Hosted PBX services cost $30-$100 per month per user, so the benefit of outsourcing your call routing is greater as your user count grows.
ICG Communications' VoicePipe service connects a network of VoIP phones to a managed telephony applications suite using a single IP WAN link or VoATM (Voice over ATM) connection. In this fashion, the hosted PBX provider is responsible for maintaining the telephony switching servers and dial-plan, and it often means that the subscriber cannot integrate its own PBX with the service. Check with your prospective provider to see what it supports. 16.5.1.4 Web-based call center servicesA relatively new entrant into the TSP arena is the web-based call center provider. A step beyond the hosted PBX model, this type of service provides ACD, IVR, call queues, and other features commonly required in call centers and hosts them like an application service provider (ASP) at an off-site data center. VoIP is used to connect the call center endpoints with the ASP's backend. Companies offering this service include:
Some smaller-scale call center services geared toward the small/medium business sector are available from Vonage and Packet8, too.  |
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