Developed by the IETF, the international organization responsible for the web protocol HTTP and the mail protocol SMTP, SIP is the newest generation of communications protocols that ties the telecom and the Internet worlds together. 

SIP offers fast development timescales, lower costs both up front and ongoing and a wide choice of compatible vendors and products.

SIP has reached a critical deployment stage, with most vendors now including SIP in their corporate roadmaps, and real world services by incumbent operators are already being rolled out. 

Personal applications can easily interconnect with WAN-centric systems from various vendors. From both a carrier and an end-user perspective, this is a highly attractive scenario as they will soon no longer be locked into a single supplier or system."

The variety of SIP technologies include: softswitch-compliant media servers, testing tools, Presence products for mobile and fixed networks, softswitches and gateways, desktop phones and softphones, SIP Proxy, Registration and Applications servers, video and complete business systems all working robustly together.

SIP joins the Internet and mobile telephony with a uniform protocol, establishing a more straightforward IP data stream between future mobile terminals and various other devices connected to the Internet.

For a mobile phone user, this means, for instance, multifunctional applications that integrate voice, messaging and email in an intelligent way.

For third generation mobile communications to succeed, it is crucial that new applications and services can be developed in a fast and easy manner.

Furthermore, the Session Initiation Protocol together with Ipv6 have the potential to greatly enhance person-to-person communications by allowing each person to have a personal address on the Internet, which can be accessed across the globe in any IP-network.

In the All-IP era, numerous applications can be implemented with SIP. For instance, instead of a blinking telephone number on the display, the caller can introduce himself in the beginning of the communications session with a personalized logo or business information.

The subject of the call can then be immediately displayed to the recipient of the call. It is also possible to create richer profiles that include additional features, such as sending tailored information to predetermined callers or integrate email/media-on-demand so that the call, for example, can be forwarded to a web video mail answering service if the recipient of the call is not available.

The Session Initiation Protocol is used on the Internet and other network devices to initiate, manage and terminate interactive sessions, including voice, across an IP network. The protocol is designed to help open up the network for the creation of personalized services that incorporate voice. SIP is being developed by the Internet Engineering Task Force (IETF), and has garnered strong support among telecommunications carriers, vendors, cable operators, and Web-based voice chat providers. The 3GPP has decided to base the call set-up in 3G All-IP networks on SIP.

SIP will have an important role in the Nokia Mobile Internet Technical Architecture (MITA), and complements the work of other industry consortia. The aim of MITA is to facilitate a user-friendly mobile Internet experience.