October 15, 2012 at 18:57IP-telephony: modern technology of free calls
Introduction
Since the invention of the telegraph, the history of telecommunications dates back more than 200 years. The rapid development of telephony has led to the fact that the communication capabilities, which seemed just recently fantastic, are already being used everywhere. One of these innovations is IP telephony. Not so long ago, it would be extremely difficult to imagine voice transmission not through the usual telephone wires, but through data channels. Today, telephone networks and the Internet are combined into a single infrastructure. Voice IP traffic has already supplanted conventional telephony and is competing with cellular communications. With the development of IP-telephony, its functionality increases, and the lack of roaming on the Internet, adds free audio-video communications, the possibility of conferences, cloud services and so on.
Protocols
IP-telephony is built on the basis of several standardized communication protocols. The underlying protocol is the H.323 standard from the International Telecommunication Union (ITU), according to which transnational Internet telephony operators operate. All calls in this protocol are managed by the Gatekeeper (gatekeeper, zone controller) - a program or device located at the IP-telephony provider that coordinates all clients that are united in a common zone. Under his control are terminals, gateways, conference control devices (MCUs), etc. Thanks to gateways, the H.323 protocol can combine telephone and IP networks. So, an adapter for analog phones (eg HandyTone, GXW), which connects to the Internet and an analog phone, can act as a gateway. When dialing a number on a traditional telephone, the gateway transfers the call to the Internet, and when a call is received via IP-telephony, it allows the owner of the analog device to receive a call without using the public switched telephone network (PSTN). The gateway can be either special IP-phones (manufacturers: Gigaset, Panasonic, Cisco or Yealink), or programs on a computer to which a headset with headphones and a microphone is connected. Terminals are the end devices from which a conversation is made: smartphones and PCs with special software, IP phones. For a conference in which more than 3 people can participate, the MCU server is used. The gateway can be either special IP-phones (manufacturers: Gigaset, Panasonic, Cisco or Yealink), or programs on a computer to which a headset with headphones and a microphone is connected. Terminals are the end devices from which a conversation is made: smartphones and PCs with special software, IP phones. For a conference in which more than 3 people can participate, the MCU server is used. The gateway can be either special IP-phones (manufacturers: Gigaset, Panasonic, Cisco or Yealink), or programs on a computer to which a headset with headphones and a microphone is connected. Terminals are the end devices from which a conversation is made: smartphones and PCs with special software, IP phones. For a conference in which more than 3 people can participate, the MCU server is used.
SIP is considered more flexible and scalable, which is used by almost all IP-telephony providers, which allows not only to talk via the Internet, but also to exchange video, instant messages, play online games, etc. By the way, MTT YouMagic IP-telephony service is built exactly on it. This protocol regulates only the procedure for establishing a connection between devices, and a network protocol for streaming data transfer (SDP) is connected for data transfer. SIP has more functions than H.323, and this difference is explained by the fact that this protocol was not developed by ITU telephony operators, but by an open group of the international community of designers, scientists, network operators and providers (IETF). For the operation of the SIP protocol, proxies are required, which are installed by the IP-telephony providers, and terminals by users, that is, devices through which communication is conducted. They can be the same IP-phones, gateways, as well as computers or smartphones with installed software (softphone) and connected to the Internet.
There is also a corporate SCCP protocol that runs on the H.323 logic. SCCP was developed by Cisco special to reduce the cost of communication in companies by saving on equipment.
Codecs
For the quality of voice transmission in all protocols, codecs are responsible - algorithms for converting voice into the required digital format. In IP-telephony, voice is converted into so-called packets, which are transmitted over Internet networks. To transmit voice in good quality, without delays, echoes and distortions that turn a person’s voice into a robot’s voice, one or another codec is selected, depending on the Internet connection, software settings and other factors. So, one codec (for example, g722) with a fast and reliable Internet connection can transmit voice in high quality, but the low bandwidth of the channel will make conversation impossible due to the loss of phrases or sounds. In MTT’s YouMagic, codecs like iLBC or Silk can transmit voice without noticeable delays with low quality Internet channels, but they compress data so much,
SIP technology service - YouMagic
Consumers have long been accustomed to comfortable audibility when communicating via fixed networks and even through the networks of mobile operators, so any interference and malfunctioning in IP-telephony can discourage the desire to use it. Understanding this perfectly, each Internet telephony operator, when developing its products, has to closely monitor the status of its proxy servers and other equipment, the passage of data through the networks of other operators and other costly issues, while striving to maintain low tariffs for communication with the whole world.
One of the prime examples of maximizing the benefits of SIP is YouMagic, launched in 2011. In this purely Russian IP-telephony project, agents can be smartphones, personal computers, IP / DECT phones or regular phones complete with the special gateway mentioned above. For common operating systems, proprietary softphones have been released that allow you to talk through YouMagic on an iPhone or Android, on a Windows or Mac OS computer.
To ensure good call quality, YouMagic uses various codecs in different situations. The low quality of the Internet channel is characteristic of the domestic mobile Internet, therefore, when developing an application for smartphones, all the features of packet transfer in 3G networks were taken into account. So, the YouMagic application for Android provides automatic selection of the right codec, depending on the Internet connection. And experienced users from the list of presented codecs can independently select those that will be used in various Internet networks. Such a function allows the application to automatically adjust to the properties of the Internet connection, improving the quality of voice transmission in the dialogue.
One of the most convenient types of Internet access when using IP-telephony is Wi-Fi. Today, Wi-Fi network coverage is becoming more widespread, and quality is becoming more stable. So, it was recently announced that in 2013 work will begin to create a Wi-Fi network on all metro lines in Moscow, and ground transport will be connected. Wi-Fi is available in cafes and restaurants in many cities of Russia. It seems that after a couple of years we will be able to be in the “Wi-Fi cloud”, communicating with the whole world in any way convenient for us, and IP telephony will become one of the most comfortable ways of communication.
Traditionally, communication between users of one IP-telephony operator is free, and a call to a mobile or landline number in any country or city in the world is much cheaper than when using a mobile or landline phone. YouMagic provides its subscribers exclusively affordable tariffs: they will have to spend less than 1 ruble per minute to communicate with any city in Russia, calls to such popular countries of the world as the USA, Germany or Israel are also beneficial. And communication between all YouMagic owners among themselves, of course, remains free.
Since the invention of the telegraph, the history of telecommunications dates back more than 200 years. The rapid development of telephony has led to the fact that the communication capabilities, which seemed just recently fantastic, are already being used everywhere. One of these innovations is IP telephony. Not so long ago, it would be extremely difficult to imagine voice transmission not through the usual telephone wires, but through data channels. Today, telephone networks and the Internet are combined into a single infrastructure. Voice IP traffic has already supplanted conventional telephony and is competing with cellular communications. With the development of IP-telephony, its functionality increases, and the lack of roaming on the Internet, adds free audio-video communications, the possibility of conferences, cloud services and so on.
Protocols
IP-telephony is built on the basis of several standardized communication protocols. The underlying protocol is the H.323 standard from the International Telecommunication Union (ITU), according to which transnational Internet telephony operators operate. All calls in this protocol are managed by the Gatekeeper (gatekeeper, zone controller) - a program or device located at the IP-telephony provider that coordinates all clients that are united in a common zone. Under his control are terminals, gateways, conference control devices (MCUs), etc. Thanks to gateways, the H.323 protocol can combine telephone and IP networks. So, an adapter for analog phones (eg HandyTone, GXW), which connects to the Internet and an analog phone, can act as a gateway. When dialing a number on a traditional telephone, the gateway transfers the call to the Internet, and when a call is received via IP-telephony, it allows the owner of the analog device to receive a call without using the public switched telephone network (PSTN). The gateway can be either special IP-phones (manufacturers: Gigaset, Panasonic, Cisco or Yealink), or programs on a computer to which a headset with headphones and a microphone is connected. Terminals are the end devices from which a conversation is made: smartphones and PCs with special software, IP phones. For a conference in which more than 3 people can participate, the MCU server is used. The gateway can be either special IP-phones (manufacturers: Gigaset, Panasonic, Cisco or Yealink), or programs on a computer to which a headset with headphones and a microphone is connected. Terminals are the end devices from which a conversation is made: smartphones and PCs with special software, IP phones. For a conference in which more than 3 people can participate, the MCU server is used. The gateway can be either special IP-phones (manufacturers: Gigaset, Panasonic, Cisco or Yealink), or programs on a computer to which a headset with headphones and a microphone is connected. Terminals are the end devices from which a conversation is made: smartphones and PCs with special software, IP phones. For a conference in which more than 3 people can participate, the MCU server is used.
SIP is considered more flexible and scalable, which is used by almost all IP-telephony providers, which allows not only to talk via the Internet, but also to exchange video, instant messages, play online games, etc. By the way, MTT YouMagic IP-telephony service is built exactly on it. This protocol regulates only the procedure for establishing a connection between devices, and a network protocol for streaming data transfer (SDP) is connected for data transfer. SIP has more functions than H.323, and this difference is explained by the fact that this protocol was not developed by ITU telephony operators, but by an open group of the international community of designers, scientists, network operators and providers (IETF). For the operation of the SIP protocol, proxies are required, which are installed by the IP-telephony providers, and terminals by users, that is, devices through which communication is conducted. They can be the same IP-phones, gateways, as well as computers or smartphones with installed software (softphone) and connected to the Internet.
There is also a corporate SCCP protocol that runs on the H.323 logic. SCCP was developed by Cisco special to reduce the cost of communication in companies by saving on equipment.
Codecs
For the quality of voice transmission in all protocols, codecs are responsible - algorithms for converting voice into the required digital format. In IP-telephony, voice is converted into so-called packets, which are transmitted over Internet networks. To transmit voice in good quality, without delays, echoes and distortions that turn a person’s voice into a robot’s voice, one or another codec is selected, depending on the Internet connection, software settings and other factors. So, one codec (for example, g722) with a fast and reliable Internet connection can transmit voice in high quality, but the low bandwidth of the channel will make conversation impossible due to the loss of phrases or sounds. In MTT’s YouMagic, codecs like iLBC or Silk can transmit voice without noticeable delays with low quality Internet channels, but they compress data so much,
SIP technology service - YouMagic
Consumers have long been accustomed to comfortable audibility when communicating via fixed networks and even through the networks of mobile operators, so any interference and malfunctioning in IP-telephony can discourage the desire to use it. Understanding this perfectly, each Internet telephony operator, when developing its products, has to closely monitor the status of its proxy servers and other equipment, the passage of data through the networks of other operators and other costly issues, while striving to maintain low tariffs for communication with the whole world.
One of the prime examples of maximizing the benefits of SIP is YouMagic, launched in 2011. In this purely Russian IP-telephony project, agents can be smartphones, personal computers, IP / DECT phones or regular phones complete with the special gateway mentioned above. For common operating systems, proprietary softphones have been released that allow you to talk through YouMagic on an iPhone or Android, on a Windows or Mac OS computer.
To ensure good call quality, YouMagic uses various codecs in different situations. The low quality of the Internet channel is characteristic of the domestic mobile Internet, therefore, when developing an application for smartphones, all the features of packet transfer in 3G networks were taken into account. So, the YouMagic application for Android provides automatic selection of the right codec, depending on the Internet connection. And experienced users from the list of presented codecs can independently select those that will be used in various Internet networks. Such a function allows the application to automatically adjust to the properties of the Internet connection, improving the quality of voice transmission in the dialogue.
One of the most convenient types of Internet access when using IP-telephony is Wi-Fi. Today, Wi-Fi network coverage is becoming more widespread, and quality is becoming more stable. So, it was recently announced that in 2013 work will begin to create a Wi-Fi network on all metro lines in Moscow, and ground transport will be connected. Wi-Fi is available in cafes and restaurants in many cities of Russia. It seems that after a couple of years we will be able to be in the “Wi-Fi cloud”, communicating with the whole world in any way convenient for us, and IP telephony will become one of the most comfortable ways of communication.
Traditionally, communication between users of one IP-telephony operator is free, and a call to a mobile or landline number in any country or city in the world is much cheaper than when using a mobile or landline phone. YouMagic provides its subscribers exclusively affordable tariffs: they will have to spend less than 1 ruble per minute to communicate with any city in Russia, calls to such popular countries of the world as the USA, Germany or Israel are also beneficial. And communication between all YouMagic owners among themselves, of course, remains free.