
Gartner research vice president Steve Blood said the release is highly significant. "Skype is becoming a service provider. Skype's management has realised that they can't rule the world by being proprietary," he said.
Skype has already become established in some enterprises, brought in by staff who use the service for cheap - often free - voice calls at home. The new service offers businesses a way to provide Skype access in a more controlled environment.
"Connecting to existing standards-based SIP PBXes is a good way for Skype to start addressing the business market, and it will be interesting to see how large companies change their thinking about the deployment of Skype within the network," said Rebecca Swensen, a communications research analyst at IDC.
Nevertheless, some market watchers remain sceptical about Skype's appeal to corporate buyers. "Because the service is only in beta at present you would expect to see a number of unforeseen technical issues that will need to be resolved," cautioned Richard Thurston, an analyst with Analysys Mason.
The Skype for SIP beta program is open to a limited number of participants and targets users such as phone system administrators, developers and service partners. Firms need to have a SIP-based IP PBX installed and the technical competency to configure it.
The biggest issue for most enterprises would be security, argued Gartner's Blood.
"Inside the IP PBX world everybody does encryption, but Skype won't be encrypting between the corporate SIP gateway and Skype's firewall. They may encrypt the payload, but there's a risk if it's left open, and for some companies that risk [of eavesdropping] is going to be too much," Blood said.
"Skype encrypted their communications from PCs to their firewall and they recognised the security implications there. It'll be interesting to see how they work through the security issues associated with SIP connectivity," he added.
Despite those doubts, some enterprise users are likely to be attracted by the system's ease of use. Deployment promises to be relatively painless, as no extra hardware is required, leaving IT managers little more to do than configure call routing from their existing IP PBX out through the firewall to Skype's site.
During the beta test period Skype will be charging calls at its standard rate. A final decision on pricing will be made when the full product ships, which is expected to be later this year.
Blood argued that those prices may not be attractive enough to enterprise buyers. "It won't look that good for what the large businesses are getting in their international rates, but might appeal to mid-sized firms," he added.
Skype will need to either deliver compelling cost savings or find some other mechanism to win corporate users, argued Analysys Mason's Thurton. "Offering another cheap-to-call service is in itself not much of a selling point," he said.
Vendors such as IBM and Microsoft have the advantage in the large corporate communications market, said Blood, as their secure collaborative systems are more mature.