VoIP stands for Voice over IP. VoIP refers to communications that no longer take place through a traditional telephone network, but through an IP network.
More specifically, VoIP refers to the set of application layer communication protocols that make this type of communication possible.
The information (both the signaling to establish, manage and close the call, and the voice), instead of traveling on an analog telephone line, crosses any network based on an IP protocol.
The communication that the VoIP system allows to obtain is of the real-time audio-video, unicast or multicast type (therefore video calls and videoconferences, for example), and allows you to easily reach any type of user.
It therefore offers the possibility to make and receive calls from other VoIP numbers, analogue numbers, national numbers, international numbers, fixed and mobile users, all toll-free numbers and emergency numbers.
In the last years the development of VoIP has been very fast and its technology is constantly evolving; all of this was possible thanks to the widespread diffusion of high performance and broadband internet connections.
For data transport (the voice), in the vast majority of VoIP implementations, a set of communication protocols such as RTP (Real-time Transport Protocol) over UDP (User Datagram Protocol) over IP (Internet Protocol) are adopted. The use of UDP instead of TCP is justified by the fact that a real-time communication such as voice cannot tolerate additional or too high delays or latencies due to the retransmission of lost packets.
For the signaling (that is everything that concerns the reaching of the user, the establishment of the call, the maintenance of communication and then the closure of the call) there is a vast dominance of the use of the SIP protocol, over both UDP and TCP.
The web is full of article and video about this topic.
One of the most viewed YouTube video is this one
In this mini-series of articles I want to give my contribution on this topic. The series will be divided into the following parts:
- pilot #0: (the article you are reading) a brief introduction to the mini-series
- part #1: basic concepts of SIP
- part #2: the basic SIP headers
- part #3: SDP & RTP
- part #4: UA PBX, standard configurations and some security tips
- part #5: the main tools for working with VoIP
- part #6: audio problems and the quality of a VoIP call
- season finale #7: final conclusions
Let me know if this is an interest topic to you and if you like the lineup or if there are any topics / insights that you would like to speak about.
Writing about a topic is a way to "understand if I understand", to collect contributions (I hope there will be many comments that will confirm what I have written and many comments that will correct me) and to help the sharing of knowledge and I love all of this stuff!
Thanks a lot for reading, sharing and comment this article.
Thanks to undraw.co for the beautiful illustration I used in the header