IMS Q

IMS Q&A with Greg Papadapolous, CTO and Executive VP for Sun

Consider the difference between the two worlds I just mentioned – one centered around voice, the other centered around data. Since the birth of the telephone, we've been communicating over circuit-switched technology. The current trend is to replace it with the more efficient packet-switched technology. Yet both provide the ability to connect to the Internet, send video or instant messages. So that begs the question: why do we need IMS if I can already do these things today? There are really three main reasons: QoS, billing and integration of different services. The packet-switched domain has an interesting problem in delivering real-time multimedia services in that it can't guarantee quality level – it's like rolling the dice. As a result, the quality of a VoIP conversation can vary quite a bit throughout its duration. IMS takes care of synchronizing session establishment with a QoS provision so that users have a consistent experience.

Billing is the second big issue. In today's network, all bits sent over the wire look the same. So how can an operator tell whether you're downloading a file, streaming a video or having a VoIP call? IMS provides the necessary information about the service being delivered to the end-user so they can appropriately bill you for it.

Finally, and in my view most significantly, IMS is based on Internet technologies and Internet protocols so that all services provided by the Internet are possible on an IMS network. This means that a multimedia session between two IMS users, between an IMS user and an Internet user, and between two Internet users is established using exactly the same protocol. This makes it trivial to do interesting things like setup a conference call with a video stream while sending a snapshot of a beautiful sunset to my wife on her computer. This is why I said that IMS is network convergence at its best; it uses the circuit-switched world to provide ubiquitous access and Internet technologies to provide compelling new services.