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Words To Know. FreeSWITCH Words Defined.

By: Kathleen King Category: Blog Posted: November 27, 2017

Have you ever come across a word or acronym you didn’t know? Or maybe you have heard a word and didn’t know exactly what it meant. Learning how to utilize FreeSWITCH can be a lot of work, and learning the definitions of industry staples will make your studies much easier. You can learn more by visiting the links to our Confluence pages included with some of the definitions.

Check out the compiled list of some of the most common words or acronyms used in the FreeSWITCH community:

  • Sofia = The Sofia-SIP library is LGPL licensed and used by FreeSWITCH and others. When you see “mod_sofia” anywhere in your configuration, think “This is SIP stuff,” because this includes the sofia module and the sofia library. It takes a while to master it all, so please be patient with yourself. SIP is a crazy protocol and it will make you crazy too if you aren’t careful.



  • IP = Internet Protocol is a communications protocol for computers connected to a network, especially the Internet, specifying the format for addresses and units of transmitted data. Think of it like the dictionary and contact list your computer uses to talk to networks.


  • DTMF = DTMF (dual tone multi frequency) is the signal to the phone company that you generate when you press an ordinary telephone’s touch keys. They are the sounds associated with the number keys on most phones, and your phone uses those sounds to determine the value.


  • fs_cli = A CLI (command line interface), or specifically fs_cli, is a FreeSWITCH command line interface that helps you control your FreeSWITCH instance using commands. You can see how many active calls are running and which users are registered, or even reload configurations using the FreeSWITCH command line. So it is very much like a chat service between you and your application. You can use fs_cli to prototype long commands.



  • RTC = Real-time Communication is the idea behind being able to talk to someone in real-time as if you are having a face-to-face conversation. 


  • VoIP = Voice over Internet Protocol is a technology that enables you to transmit Voice communications over the Internet or an IP network. As long as you are talking to someone over the Internet or a computer, that is VoIP.



  • NAT = Network Address Translation (NAT) is a method of remapping one IP address space into another by modifying network address information. This means it can edit the “contact list” your computer is using to talk to networks. NAT is useful in situations where your computer has a private IP and it needs to communicate to other computers on the internet. For example, your computer will need a public IP so the external computers can speak to it, so the private IP is translated into a public IP by the routers on the network using NAT.

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