The scalability of this - or indeed any - VoIP telephony system is primarily dependent on the available bandwidth of your internet connection. To ensure good call quality you should allow available symmetric bandwidth (both up- and down-stream) of 64kbit/s in both directions for each simultaneous call. 64kbit/s produces a data rate for the compressed audio of 8KB per second each way. Packet loss or lack of bandwidth can make voice traffic choppy and unusable very quickly, so it's important to make sure your broadband connection can handle the amount of VoIP traffic you'll be generating. How much bandwidth you'll actually need depends on how many simultaneous calls you expect to be making a call centre could expect to have 90 per cent of users on calls at once, while a normal office would have 50 per cent or less simultaneous use.
Gradwell estimates that an ADSL line with 256k upstream should handle three to four concurrent calls and recommends that users who use their service to provide phone lines to up 10 people should dedicate one broadband service to their phone provision. We agree on this.
Gradwell charges 3 per Direct Dial Inward (DDI) phone number per month for inbound calls. For each number, they guarantee two concurrent call channels of 80kbit/s. If you want outbound calling, Gradwell charges a setup fee of 20 and then applies call charges as listed on the website. You can even transfer your existing phone numbers to your Gradwell DDI for a fee of 20 per line. Gradwell can also provide a suitable high-bandwidth internet connection to handle the amount of traffic generated by VoIP telephony, although you aren't obliged to use its broadband service. If you want to source all your services from a single provider, its Premier Plus broadband service costs 65/month and should handle up to 20 simultaneous calls. This is a little small-scale for medium-to-large businesses but is a good fit for SMEs.
Verdict
At just £3 for a supported inbound line, Gradwell is already competitively priced by the standards of enterprise VoIP providers. If your office is exclusively Microsoft-based then there are plenty of advantages to OCS, such as its seamless integration with Outlook, despite the inherent challenges in configuring it. Gradwell's OCS service removes a major stumbling block – OCS' incompatibility with standard VoIP services. As the only specialist provider of OCS VoIP that we know of, the advantage is obvious.
Requires: Microsoft OCS server, Microsoft Communicator clients; broadband connection
