Today, VoIP technology develops and is strongly applied in all areas of life. SIP protocol is the main protocol in the communication of VoIP system. So let’s find out What is SIP in the following article!
1. What is SIP?
SIP – Session Initiation Protocol is a signaling protocol used to establish an online session between 2 or more participants, modify that session, and finally terminate it.
The concept of SIP
It has found its primary use in the world of IP Telephony. The fact that SIP is an open standard has generated great interest in the telephony market, and manufacturers of SIP-based phone carriers have seen tremendous growth in this area.
2. Relationship between VoIP and SIP
The relationship between VoIP and SIP can be understood similarly to the relationship between web pages and HTML. A website is a collection of pages accessible by a web browser, and HTML is a language that you can use to build websites. However, most websites also use other languages like Java.
Relationship between VoIP and SIP
Similarly, VoIP refers to any method of sending voice calls over the Internet. SIP is just one of many protocols currently in use. So you can do VoIP with other protocols. Not every VoIP system will use SIP but the majority of VoIP services use SIP as it is the industry standard.
3. Why is SIP important
A protocol is a system of rules for exchanging information between pieces of hardware. Modern digital services use many protocols such as SIP, TCP, HTTP… A protocol that defines the syntax and semantics of the communication. For a protocol to be useful, different vendors must agree to use it across devices and applications. Over time, many protocols evolved to become industry standards as the vast majority of developers started using it.
SIP is one such industry standard used in VoIP. Most organizations choose SIP because they can be sure of interoperability. You can buy SIP-compatible hardware and know it will work with your system. You don’t have to worry about compatibility and integration issues.
4. Features in SIP protocol
Features of SIP protocol
The SIP protocol includes the following features:
- The SIP Invitation is used to create a session and carries a session description that allows participants to agree on a set of compatible media types.
In this way, SIP is not restricted to any particular media type and can therefore handle an extended range of communication technologies.
- SIP allows users to move through a mechanism that allows requests to be authorized or redirected to the user’s current location. Users can register their current location with their home server
- SIP supports end-to-end and hop-by-hop authentication, as well as end-to-end encryption using S/MIME
- Members in a SIP session can communicate using unicast or multicast relationships, or a combination of both. In addition, SIP is independent of the lower layer transport protocol, allowing it to take advantage of new transport protocols
- Software that implements the underlying SIP protocol can be extended with additional capabilities and is actively being exploited for a variety of communication applications.
5. Structure of the SIP protocol
The SIP protocol is text-based and has significant similarities with the HTTP protocol. Text-based messages and request response mechanisms make troubleshooting easier.
The actual data transmission is done by Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) on layer 5 of the OSI model. The Session Description Protocol (or SDP) controls which protocol is used.
SIP messages describe the identities of the call participants and how participants can communicate over the IP network. Encapsulated inside SIP messages we can also sometimes see an SDP declaration.
SDP (Session Description Protocol) will determine the type of communication channel to be established for the session – typically this will declare what kind of code is available and how communication tools can reach each other over the IP network .
Once this setup message exchange is completed, the media is exchanged using another protocol, typically RTP (Real Time Transfer Protocol).
SIP was developed by the IETF and published as RFC 3261, and its versatility has allowed it to almost completely replace the H.323 protocol in the VoIP world.
Above is all the information about SIP that we want to share. Good luck!