Skype

Skype (pronounced to rhyme with ripe) is a peer-to-peer internet telephony (VoIP) network, founded by Niklas Zennström and Janus Friis, the creators of Kazaa. The network is provided by all combined users of the free desktop software application. Skype users can speak to other Skype users for free, call traditional telephone numbers for a fee (SkypeOut), receive calls from traditional phones (SkypeIn), and receive voicemail messages.

Features

The Basic computer-to-computer service allows users of the Skype software to send voice or text messages to one another from their computers via the Internet at no cost. Conferences of up to five users are supported.

SkypeOut

First Beta on or before June 15 2004 with credit purchase by voucher, SkypeOut allows Skype users to dial regular telephones. Calls (including tax) cost 0.017 Euro per minute to many countries (including the U.S., Canada, Chile, Western Europe, Australia and New Zealand), with calls to mobile or cell phones often costing more. Rates rise to over 1.00 Euro per minute for calls to certain isolated islands (the country of the originating user is not a factor in determing cost). Almost any telephone can be dialed from Skype..

SkypeIn

SkypeIn allows Skype users to receive calls on their computers dialed by regular phone subscribers to regular phone numbers. Beta released March 10, 2005, SkypeIn permits users to subscribe to numbers in UK, USA, France, Hong Kong, Denmark, Finland, Norway and Sweden. Cost is 30 Euro for a 12-month subscription, or 10 Euro for a three month subscription.

VoiceMail

Voicemail was also released on March 10, 2005. This service allows callers to leave voice-mail messages for Skype users who are not online, on another call or otherwise indisposed. This can be purchased separately or it is bundled with SkypeIn.

Other features

Version 1.2 for Windows was released in March 23, 2005. Its most significant new feature is the provision of centrally-stored contact lists so that a user's contact information is available from any computer that is connected to Skype (in other previous versions, contact information was stored on the local computer).

Versions now exist for Microsoft Windows (Windows 2000, Windows XP and Windows CE (Pocket PC)), Mac OS X and GNU/Linux.

Technology

Each Skype user must have the Skype software running on his computer. This software is available for free and can be downloaded from the company website. The Skype code and protocol remain closed and proprietary.

The main difference between Skype and other VoIP clients is that it operates on a peer-to-peer model rather than the more traditional server-client model. The Skype user directory is entirely decentralized and distributed among the nodes in the network, which means the network can scale very easily to large sizes (currently just over ten million users) without a complex and costly centralized infrastructure.

Skype also routes calls through other peers on the network, which allows it to traverse NATs and firewalls, unlike most other VoIP programs (notably those based on the SIP protocol, see article). This, however, puts extra burden on those who connect to the Internet without NAT, as their computers and network bandwidth may be used to route the calls of other users. The selection of intermediary computers is fully automatic, with individual users having no option to disable such use of their resources. This fact is not clearly communicated, however; in fact, it seems to contradict the license agreement which would limit Skype’s utilization of the user’s “processor and bandwidth [to the] purpose of facilitating the communication between [the user] and other Skype Software users” (section 4.1).

Security

Since a Skype connection may be routed through an intermediate peer, 256-bit AES encryption actively encodes the data stream of each call or instant message. Skype uses 1536 to 2048 bit RSA to negotiate symmetric AES keys. The Skype server certifies each user's public key at log in.

Since the Skype code is not public source, the security of the software cannot be readily established. It opens several ports on the user's computer and directly manipulates Windows XP's built-in firewall.

History

• April 23 2003 Skype.com and Skype.net domain names registered
• August 29 2003 First public beta version released
• June 15 2004 Beta release of version 0.98.0.28 with first support for SkypeOut. Credits only available by voucher
• June 27 2004 SkypeOut credits first available for purchase on Skype website.
• July 27 2004 Release of Version 1.0 for Windows
• October 20 2004 First time 1 million Skype users are online at once
• February 14 2005 First reached 2 million online
• March 10 2005 SkypeIn Public Beta starts
• March 11 2005 Skype press release reports 1 million Skype-out users and 29 million registered users
• March 11 2005 Software has been downloaded 84 million times and 5.98 billion talk minutes served
• April 15 2005 Downloaded more than 100 million times

Skype has established partnerships with online web properties including Tom.com, PcHomeOnline, Daum and Livedoor as well as hardware manufacturers including Plantronics, Logitech, Motorola, VTech, RTX and Siemens. Another boost to the distribution of Skype came in November 2004 when Kazaa bundled Skype with version 3.0 of its software.

Graphs

See also

• Comparison of instant messengers
• Voice over IP

External links

• Official Skype Website
• Official Skype Discussion forums

• An Analysis of the Skype Peer-to-Peer Internet Telephony Protocol
• Look2Skype.com – Outlook Skype Add-in. Skype Contacts from Outlook
• Opinion piece advocating Skype and similar technologies
• Jyve.com Portal to Everything Skype – Community, Language Learning, Yellow Pages
• SAM – Skype Answering Machine
• SomeoneNew.com – Skype Dating site – search for Skype users with common interests
• Skype Headset Reviews – Helps users to identify which headset is most suitable for them
• Skype Journal
• SummitCircle.com – Find Skype phones, add-ons and communities.
• YapperNut.com – Telephone Gateway that Connects a Regular Telephone to Skype