Skype 1.4

Skype is the big name in peer-to-peer Internet telephony after hitting the headlines with its $2.6b sale to eBay - which seems unbelievable considering their main product is freely downloadable and so are most of their competitors. But what sets Skype apart from most other VoIP clients is a mature, full featured client that offers unsurpassed voice quality.

Skype is an internet telephony (VoIP) network which allows its users to call and speak to other Skype users for free. To do this, you simply search for other Skype users on the network and make calls to their PCs using a microphone attached to your PC. You can also make calls to traditional phone lines, but this service is charged.

Unlike the majority of VoIP client software out there, Skype doesn't use SIP (Session Initiation Protocol) combined with RTP (Real-Time Transport Protocol) for calls but instead uses its own proprietary technology which provides calls of remarkable clarity. However, this is also the principal downfall of Skype in a market where broadband providers are increasingly offering SIP based hardware handsets and services to their customers - Skype users can only make free calls to other Skype users, and the technology lock-in means the SkypeIn and SkypeOut services are the only way to connect to Plain Old Telephone Systems (POTS).

Being a peer-to-peer system, Skype offers more than just the basic call setup/teardown functions of SIP and H.323. Users can advertise their availability like in an IM client - available, offline, busy etc. In fact it includes an IM chat client as well. It also offers a centralized directory for searching and connecting to other Skype users - recent estimates suggest upwards of 70,000,000 Skype clients have been downloaded. A nice feature is the "Skype me" search function which locates anyone with the "Skype me" status set - this means they welcome random conversations with strangers who just want to chat. Skype users can also block users from calling them or seeing their status, or set their mode so the only people who can ring them are the ones they authorize. If only a normal telephone could do that.

The interface is clean and easy to use, and the address book can import contacts from Outlook and automatically search the Skype directory for them. It also supports vCards. As for connectivity to POTS - it couldn't be easier. Just login to the Skype website and buy some credit and SkypeOut can be used to dial regular phone numbers anywhere in the world - Skype's backend servers will route the call out their gateways to deliver low cost long-distance calls just like using a calling card. SkypeIn provides a unique phone number that can be used to dial Skype from normal telephones and there is the subscription-based Skype Voicemail service.. Of course, with their lock-in you can only use Skype's service, which is undoubtedly the reason why Skype doesn't support SIP connectivity. That's a shame because it is about the only thing it's missing.