What is Skype?

Skype is an internet communication system, that allows users to make free voice calls basing on the VoIP technology as well as to use the service of calls to the telephone network of general use (landline and mobile numbers) for a fee. Skype features allow the users to create online-conferences (up to 25 persons), exchange text messages, communicate in video mode and send files.

Skype is compatible with different operating systems, including Windows, Mac OS, Linux, Windows Mobile, iPhone, PSP and others. The Skype software is free, so everyone can download and install it.

Services

There are free-of-charge and paid services available in Skype. The following services belong to the paid ones: SkypeOut, SkypeIn and Voice Mail.

SkypeOut is a service that allows users to make worldwide calls to the landline and mobile numbers of general use. The by-the-minute tariffing depends on the call direction.

SkypeIn is the service that allows to rent a real phone number in 14 countries of the world.

Skype To Go is the service that provides a local phone number.  Having registered such a number in one of the available countries you can use Skype tariffs from your mobile phone or even a telephone booth. Having called the local number you will be offered to dial the phone number of the person you wish to call. The charge for such a phone call with the Skype-To-Go-service consists of the price for a local call (according to the tariffs in the particular country) and the Skype tariff.

Skype Prime is a unique service that allows the Skype users to earn money with their skills. With Skype Prime the user can give paid consultations to other Skype users through voice or video calls. Having signed in for this service the user defines the charge for a minute or for the whole call. The Skype company’s fee makes up 30% of the consultant’s earning.

SMS sending service allows the user to send text messages to any mobile number all over the world. To use this service you have to refill the balance.

Redirection is a service that allows to forward the call, aimed to the Skype customer, to a landline or mobile phone of any operator all over the world. The charge for the redirected call is paid by the customer, who set the redirection.

File sending service allows Skype users to exchange files of any size. The data transfer proceeds on the base of Peer-to-Peer technology, so the transferring speed depends solely on the channel’s bandwidth.

Calls and text messages to Skype users are free of charge.

Filling up the balance 

For making calls to landline and mobile phones the balance should be refilled.

There are following ways to refill the balance: internet-services, payment terminal, credit card, electronic cash etc. The price for calls all over the world is individual for every call direction.

The customer’s location is not considered in the definition of the call price. Only the city that is being called is important. In this way, all landline calls are classified and charged as international calls.

Technology

The data transfer in Skype works on the P2P-technology. Effective algorithms of data compression allow users to connect by the minimal speed of 33,6 kbit/s. The video communication needs the speed of at least 256 kbit/s  for stable working. The program has a high-quality algorithm of data encryption (AES-256), that is used at the moment of establishing connection between computers. The decompression of the speech proceeds practically without any quality losses.

The data transfer between computers is performed with the VoIP secured protocol. The use of VoIP allow to significantly reduce the bandwidth for the data transfer. The VoIP technology provides the traffic reducing because of blocking the transmission of pauses in speech.

The speech transfer delays (from 15 to 45 ms) in th VoIP technology can be explained either by buffering the information, or by data conversion into a more acceptable form.