How it works
SIP allows to drastically decrease communication costs, as all calls made via this protocol are free anywhere in the world. You can get a SIP address and use a SIP application also for free.
SIP became popular as it offers a direct, easy, and convenient connection between traditional telephone communication and the Internet. That is why many companies have used this protocol to streamline their corporate communication.
It is worth noting that SIP can be used in any systems which need to have an established connection and to exchange data. Those might be notification systems, mobile points of sale, and others. The RFC series of documents regulate the use of SIP in such cases.
It’s easy to get started, you just need to register a SIP address, download and configure a SIP client. After this, you can make calls.
Architecture
SIP is based on a client-server architecture. Clients send requests with details of the expected server response. The server processes requests and then sends responses. In addition to information for the client, the response may also include a notification of a successful request or error details.
The call itself is maintained by distributed SIP network elements. The subscriber terminal controls the connection management. Other parts of the network are responsible for packet routing and ensuring the operation of additional services.