A Signaling Protocol for Real-Time Communication

Session Initiation Protocol (SIP) is a signaling protocol used for establishing, modifying, and terminating real-time communication sessions over IP networks. SIP enables users to create, modify, and terminate two-party (unicast) or multiparty (multicast) sessions, including:

- Voice calls
- Video conferences
- Instant messaging
- Online gaming

1. Session Initiation Protocol R.Puja Sharma, MTWU.

2. Introduction to SIP Protocol SIP-Session Initiation Protocol SIP is a signaling protocol used to create,manage and terminate sessions in an IP based network. SIP is used in internet telephony,in private IP telephone systems,as well as mobile phone calling over LTE.

3. Features: SIP is a lightweight,transport-independent,text based protocol. It can be used with UDP,TCP,ATM,etc . It is text- based,allowing for low overhead It is primarily used for VOIP calls.

4. SIP Methods and Functions INVITE : Initiates a session or call. ACK: Confirms receipt of an INVITE request. BYE : Terminates a session or call. CANCEL : Cancels an outstanding INVITE request. REGISTER: Registers a user's contact information with a SIP registrar. OPTIONS: Queries the capabilities of a SIP server or user agent. INFO : Provides mid-session information, such as DTMF (Dual-Tone Multi-Frequency) tones. PRACK : Provisional acknowledgment of an INVITE request. SUBSCRIBE : Requests notification of events, such as presence information. NOTIFY : Notifies a user of events, such as presence information. PUBLISH : Publishes presence information to a SIP server. MESSAGE : Sends instant messages.

5. SIP Methods and Functions Session Establishment: Sets up a new session or call. Session Management: Manages an existing session, including modifying or terminating it. User Location: Determines the location of a user or endpoint. User Authentication : Authenticates users and ensures secure access to SIP services. Call Routing : Routes calls to the appropriate destination. Call Forwarding : Forwards calls to another endpoint or voicemail. Call Hold : Puts a call on hold. Call Transfer : Transfers a call to another endpoint. Conference Calling : Establishes a conference call with multiple endpoints.

6. Conclusion and Future of SIP SIP has emerged as a versatile and widely adopted protocol for managing multimedia communication sessions over IP networks. Its ability to facilitate voice, video, and messaging services has made it an essential component of modern communication systems.