Session Initiation Protocol - Wikipedia, the free encyclopedia

Session Initiation Protocol - Wikipedia, the free encyclopedia

SIP Tutorial - Cartoon Way

source: www.hotsip.com

SIP - Overview

SIP

What is Session Initiation Protocol (SIP)? Why do the world’s leading communications carriers, application developers and equipment manufacturers believe that SIP is the most radical innovation in communications since the development of HTTP ignited the World Wide Web?

Like the HTTP (Hyper Text Transfer Protocol) standard on which it is modeled, SIP is a communications protocol, an agreed-on set of standards that define how devices (computers, telephones, mobile phones) exchange information with each other. HTTP, for example, set the stage for the World Wide Web by establishing how PCs accessed and displayed Web pages stored on central servers — turning the Internet from a text-based medium to a pervasive medium that has fundamentally changed our lives. SIP promises to have the same impact on how we communicate in real-time: on mobile or standard phones, via instant messaging, or over any type of IP-based device. SIP is a signaling protocol that can set up and manage any of these types of sessions, regardless of the media type (phone call, IM, game, or even live video). In fact, SIP’s power stems from its simplicity and flexibility. SIP is a certified standard of the Internet Engineering Task Force (IETF), the global nonprofit Internet technical standards body behind HTTP and Internet protocol (IP).

SIP originated in the mid-‘90s as a simple method for inviting people to view multicast sessions such as space shuttle launches over the M-Bone, the Internet’s multimedia channel. Because of its simplicity, power and extensibility, SIP was rapidly adopted for other uses across the IETF, most notably as a Voice Over Internet Protocol (VoIP) standard. Communications service providers saw VoIP as a way to merge their disparate voice and data networks. SIP offered them a new degree of scalability, interoperability and ease-of-building new services that was lacking in earlier, more telecom-centric VoIP protocols such as H.323.

From its inception, SIP was modeled closely after HTTP. Like HTTP, it was designed to work over IP networks. Also like HTTP, it significantly lowered the barriers to developing and deploying rich, innovative services by moving control of applications to the endpoints. One of the most powerful concepts of the Internet is the fact that applications can operate between a web server and a browser with no dependence on the underlying IP network. The same is true for SIP-based sessions. A SIP server and client have complete control over their session (voice, video, messaging, instant messaging, presence). This is in direct contrast to the model for service control in the traditional circuit-switched telecom world, where endpoints like phones lack call control capabilities and all services are controlled by a central switching element.

The Power of SIP

The brilliance of the SIP model stems from the following characteristics:

Control Over Services is Pushed Out to the Endpoints
In the traditional telecom environment, centralized switching elements controlled voice and other services, which significantly increased the time and cost required to build new services. By moving service control out to the endpoints (such as SIP-based mobile phones or PC clients), SIP eliminates the need for a central switching element. Because of this, it promises to bring the low development costs and fast development cycles of Web-based services to real-time communications services.

Flexibility
As a signaling protocol, SIP is session and message agnostic. While it can set up any session (voice, video, messaging, games) it carries no predefined rules for what that session should be. While it can transport messages, it supports any MIME (Multipurpose Internet Mail Extensions) type in the messages. This gives SIP the ability to support the broadest set of subscriber services — including the creation of new applications never envisioned by standards groups. Jonathan Rosenberg, dynamicsoft’s chief scientist, has often stated that “The market, not the standards bodies, should pick successful services.” SIP was designed with this philosophy at its core.

Extensibility
SIP can easily be extended to support new messages and even new types of services. Like HTTP, SIP’s capabilities can be augmented as new requirements emerge. For example, SIP for Instant Messaging and Presence (SIMPLE) is a SIP extension to support interoperable instant messaging and presence systems. Despite its extensibility, SIP is designed to remain interoperable and “backwards compatible.” If two SIP endpoints do not jointly support a set of SIP extensions, they can agree to ignore those extensions and use the base protocol for their communication.

Integration with Internet Standards
SIP provides full integration with open Internet standards and technologies. It uses URIs (Universal Resource Indicators) DNS (Domain Name Server), MIME (Multipurpose Internet Mail Extensions) in ways that are compatible with other IP applications. This allows SIP to easily interoperate with Web applications, a critical capability in building compelling mobile services. With SIP, mobile carriers can deploy services that seamlessly integrate voice, presence, messaging and instant messaging with Web interactions, providing the foundation for a virtually limitless set of service possibilities.

Because of its extensive capabilities, SIP has enjoyed phenomenal market success. SIP is being used extensively today to support a broad range of voice, instant messaging and presence-based services over mobile, wireline and IP-based networks.

source: http://www.dynamicsoft.com/innovation/sip.php

Telecom Industry - Preview

Telecom industry is in pace where many technologies are pooling in to reach many. In India the telecom sector went in an all time high growth as the prices went down. The companies can withheld their margin despite the low-price offering of their service. This is achievable because of use of technology to the max. Still there are miles to achieve in this specific sector.