If you "call" and no one answers, SIP determines that a user is not available. User availability is simply a method of determining whether or not a user would be willing to answer a request to communicate.
#Sip definition it registration
Depending on the registration point chosen, there may be several different locations registered simultaneously. Voice over-IP (VoIP) phones, cellular phones, or even complete teleconferencing systems can be registered as well. When a soft-phone is activated on a laptop, it sends out a registration to the SIP server announcing availability to the communications network. SIP determines user locations by a registration process. SIP does this by providing five different functions: User Location SIP FunctionalityĮxactly what does SIP do? SIP provides the set-up/establishing, tying together, and tear-down/ terminating of multimedia communications. With the desire to keep SIP as flexible as possible, most of SIP's message and header field syntax is derived from the HTTP/1.1 specification, but is not tied to the HTTP/1.1 protocol. This means that it can work in and between IPv4 and IPv6 models. SIP works between the session and application layers of the OSI model and is not confined to any one IP version. The "session," however, is not a maintained connection as many enterprises have come to think of sessions. Also, SIP uses request/response transactions. SIP is a text-based protocol, but also carries a lot of non-text information. Whether it uses radio waves, wired-networks, satellites, etc., SIP only needs to be able to communicate. SIP does not determine what services are being sent back and forth, nor does it affect how information is passed. SIP is responsible for user location, availability, capabilities, and session setup and management. This flexibility has given SIP an advantage over other "telecommunications protocols," and is why many enterprises are eager to develop, implement, and use SIP. That being said, SIP is flexible and open enough to allow developers to build their own "hooks" into SIP. The key to SIP is that it provides only five functions: user location, user availability, user capabilities, session setup, and session management. This is one of the great things about SIP over its predecessor protocols (H.323) it does not have to be redefined to move onto something better. While SIP uses these protocols, it is not tied to them if a better solution arises.
Other standardized protocols control access to the public-switched telephone network, as well as describing multimedia sessions. The SIP typically will use the Real-Time Session Protocol (RTSP) to provide transportation and quality of service (QoS) feedback for streaming media. SIP is a component of a complete multimedia architecture, and relies on other Internet Engineering Task Force (IETF) protocols.
#Sip definition it how to
As long as the end-points (users) agree on what is being sent and how to view, listen, and so on, SIP can provide the session.
#Sip definition it full
For example, we can talk – choose a language, use a modem for data, or even pump the modem full of multimedia services. The telephone line doesn't provide a service it provides the ability to connect services. For example, consider SIP a regular telephone line. SIP is a primitive in that it does not provide services it provides a conduit for services. SIP also brings Web 2.0 concepts into fruition, but in a completely different manner. While H.323 provided an all-in-one solution, it was not flexible enough to provide for much beyond voice services. Many protocols came before SIP, such as H.323. As telecommunications migrates toward being able to provide comprehensive IP services, a standard method of providing sessions is needed. Meanwhile, the telecommunications industry has grown from providing voice, then video, and now data services. The enterprise has grown from data services and is working towards adding voice and video services over the network. Enterprises have worked for many years to provide triple-play - voice, video, and data - services. SIP is the conduit that will bring together the enterprise and telecommunications to provide IP-based communications. Why? Simply put, the Session Initiated Protocol (SIP) is the means to an end, bringing about the convergence of communications. "SIP, SIP, SIP" that's all we hear lately.
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