Convergence of Telecommunications and Inter Networks

By: Mary Nolan

Converge is the title of a project being run by TSSG to investigate the above issue. Since their initial development over thirty years ago, computer communications systems, particularly the Internet, have been designed independently of Public Switched Telecommunications Networks (PSTN). These systems have sometimes interacted, particularly in the use of the PSTN to carry Internet traffic, but attempts have just recently begun to really converge the services provided onto a single integrated network architecture.

These convergence attempts have been motivated by the fact that one of the key requirements in deploying a pervasive and ubiquitous information superhighway is the development of a global integrated telecommunications infrastructure. This global communication network will have to deal with a wide spectrum of traffic characteristics, because the network will have to support, simultaneously, applications that have a wide range of expectations and requirements.

The reasons for the fundamentally different designs of the PSTN and computer networks are several. The PSTN was developed to carry telephone calls, whereas the Internet and other computer networks were intended to transfer asynchronous data between computing devices. Telephony has strict quality of service (QoS) constraints - the user will not tolerate significant time delay, variation in this delay (jitter), loss of communication or unavailability of service.

By contrast, computer communications services have not had such stringent time constraints. Delays of the order of seconds have been considered acceptable. Access to a computer network has generally been with sophisticated devices that are capable of recovering from data loss in the network (i.e. requesting resend of packets, etc). Thus a "best-effort" communications service was considered sufficient.

The different evolutionary paths and different levels of quality of service guarantee have resulted in fundamentally different approaches to charging for the use of these two networks. PSTN users primarily pay for usage on the basis of time and distance, since a fixed portion of a limited resource is guaranteed to the user for the duration of a call (to provide quality of service). By contrast it is unreasonable to ask users to pay for usage of best-effort Internet services where no guarantees of quality of service can be made. Thus, payment for computer communications services has generally been on a monthly flat-rate basis (any time-based charges are just for access over the public telecoms network).

Three major aspects of this convergence are being investigated:

* Quality of Service - mechanisms for delivery of telecoms services over the Internet with sufficient quality guarantees.
* Accounting - pricing of future quality Internet services (while maintaining revenue streams for telecoms companies); systems are required to account for usage and charge correctly.
* Security - granting users access to services (i.e. authorisation); authentication of users (so the correct user is billed); enhancement of privacy of user communications and integrity accounting data gathered.