“Naked SIP” is SIP without IMS. Naked SIP is disruptive as we shall see below.
Wikipedia provides a comprehensive definition of IMS .
The IP Multimedia Subsystem (IMS) is a standardised Next Generation Networking (NGN) architecture for telecom operators that want to provide mobile and fixed multimedia services. It uses a Voice-over-IP (VoIP) implementation based on a 3GPP standardised implementation of SIP, and runs over the standard Internet Protocol (IP). Existing phone systems (both packet-switched and circuit-switched) are supported.
The aim of IMS is not only to provide new services but all the services, current and future, that the Internet provides. In this way, IMS will give network operators and service providers the ability to control and charge for each service. In addition, users have to be able to execute all their services when roaming as well as from their home networks. To achieve these goals, IMS uses open standard IP protocols, defined by the IETF. So, a multimedia session between two IMS users, between an IMS user and a user on the Internet, and between two users on the Internet is established using exactly the same protocol. Moreover, the interfaces for service developers are also based on IP protocols. This is why IMS truly merges the Internet with the cellular world; it uses cellular technologies to provide ubiquitous access and Internet technologies to provide appealing services.
From the above definition, we see that SIP is at the heart of IMS.
The following definition of SIP is adapted wikipedia
Session Initiation Protocol (SIP) is a protocol for initiating, modifying, and terminating an interactive user session that involves multimedia elements such as video, voice, instant messaging, online games, and virtual reality. It is one of the leading signalling protocols for Voice over IP, along with H.323.
SIP clients traditionally use TCP and UDP port 5060 to connect to SIP servers and other SIP endpoints. SIP is primarily used in setting up and tearing down voice or video calls. However, it can be used in any application where session initiation is a requirement. A motivating goal for SIP was to provide a signalling and call setup protocol for IP-based communications that can support a superset of the call processing functions and features present in the public switched telephone network (PSTN). The SIP Protocol by itself does not define these features, rather, its focus is call-setup and signalling. Some basic functions being implemented by SIP are currently being done by the SS7 network(signalling system 7 network) within the telecoms industry. SIP can do what SS7 does currently but it can do a lot more especially when it comes to multimedia sessions.
From the above, we see that
a) SIP is primarily involved in setting up and tearing down IP sessions.
b) On the web, SIP is used for peer to peer sessions
SIP and IMS go together because peer to peer does not work well with mobile. In a true peer to peer session, there would be no intervening server component. The devices would communicate directly with each other. This could lead to problems in some situations. For example, if the device is out of coverage, in the absence of a server component; no message could be left. Thus, a network component is required. That network component is IMS. Hence, in a traditional telecoms situation, IMS and SIP go together because SIP sets up and tears down the IP session and IMS provides the back end function including quality of service, support services to call management etc.
However, SIP and IMS need not necessarily go together!
There is a great report on this topic by Dean Bubley who blogs at disruptive analysis blog.
In a nutshell, from the report hightlights page:
• SIP – an essential basic subcomponent of IMS – is much easier to implement than a full IMS software framework. SIP-capable phones are already shipping.
• There are many interesting non-IMS applications of SIP on mobile phones, such as VoIP, Internet IM, enterprise IP-PBX access, or interactive games.
• In total, 787m SIP-enabled mobile handsets will ship in 2011, of which 40% will be smartphones. Europe will account for 50%+ of SIP handset volume shipments until 2010, although Japan and Korea lead, in penetration terms.
• “Naked SIP” phones, on which 3rd-party applications can exploit the SIP stack, will grow rapidly in importance, with 48m shipping in 2006, more than 220m in 2008 and 500m+ in 2011. This is a huge threat to mobile operators.
• Naked SIP will be enabled by smartphones OS’s, virtual machines like Java, and the inclusion of “exposed” SIP in many featurephone platforms.
• Although some devices will support both naked SIP and operator-oriented IMS applications, there will be 1 billion more naked SIP handsets shipped, than operator-only “closed IMS” phones, between 2006-2011.
• Internet brands, enterprises, 3rd-party developers and competing service providers will exploit the opportunities from the 1.6 billion “naked SIP” phones that will ship between now and 2011, using on-handset software clients.
• Some operators will attempt to block “parasitic” 3rd-party SIP applications, by “locking” handsets or intercepting network traffic. These attempts will seem clumsy and vindictive, and will likely drive churn and customer disloyalty.
So, what does this tell us?
‘SIP only’ phones could be numerous. They could run useful applications from third parties. They don’t need IMS. They could be true ‘peer to peer’. You could place a VOIP call to such phones from the web because they contain the VOIP stack and the SIP stack.
This makes (naked) SIP + third party applications and not IMS the more disruptive technology!
Image source: (I am sure people would be interested in this one!) ..
Google images + http://burntelectrons.org/media/moznews/mozillanews-naked.jpg