by Luciano Lenzini and Dino Giuli
Within the framework of the CNR Telecommunication Project and in cooperation with the public network operator SIP, an experimental wideband network, known as the Tuscan MAN (Metropolitan Area Network), has been developed in the urban areas of Florence and Pisa. The network currently links several research laboratories and other cultural institutions and is now being experimented.
The institutions chosen for the first installation of the Tuscan MAN were selected carefully in consideration of the particular role that they could play in the experimentation of the new broadband means of communication. A series of trials is now being carried out on the basis of a close collaboration between the scientific community, SIP and the network equipment suppliers. The main aims are:
Experimentation has been organized in two stages: the first began around two years ago and finished in December 1993; the second has been operational since January 1994. The configuration of stage 1 of the Tuscan MAN consists of a total of nine users located in Florence and Pisa (see Figure 1). The network equipment is based on QPSX, which was the starting point for the IEEE 802.6 standard (DQDB, Distributed Queue Dual Bus) defined for MANs. In each of the two sites, a main ring, operating at a speed of 140 Mbit/s, links together the Edge Gateways (EGW). Each EGW has an access network that terminates with a Customer Gateway (CGW), on the user side. The link between EGW and CGW was developed at a speed of 34 Mbit/s. Each user is linked with his own CGW in order to monitor the distribution of the traffic parameters and his/her statistical profiles. The CGW is equipped with interfaces for LAN, Ethernet IEEE 802.3, with bridge functionalities. The subnetworks in Pisa and Florence are linked by a Subnetwork Router (SR) using a 34 Mbit/s communication link. The network is supervised by a Network Management Center (NMC). The applications experimented in Stage 1 were oriented towards tele-medicine, environmental monitoring, communication aids for the disabled and tele-education. Other users (see Figure 2) and applications have been added in Stage 2.
Twelve further users in Florence and six in Pisa were chosen on the basis of the results of the first stage and in light of the emerging demand for new services and applications. During Stage 2 the network access capacity was also enhanced for those users involved in Stage 1. In fact, in addition to the LAN interfaces of type Ethernet/IEEE 802.3, with bridge functionalities, in some cases interfaces were supplied for isochronous links at 2 Mbit/s, based on the Racc. CCITT G.703.
Whereas in Stage 1 only CGW-EGW couples were used, some new users in Stage 2 have direct access to 2 Mbit/s at the main ring through the Customer Network Interface Unit (CNIU). This should lead to a greater diffusion in the number of accesses to MAN for a set of users whose communication data requirements can be met with medium speed links. Four new users (two in Florence and two in Pisa) have been linked to the main ring via direct accesses at 2 Mbit/s in order to test the Switched Multimegabit Data Service (SMDS) in the field and to assess the integrating capacity of this service on MAN.
In addition, to improve the supervision and control of both the Pisa and Florence subnetworks, a second NMC with respect to the one already located in Florence and operational in Stage 1 has been judged necessary. This will be remotely located at the SIP headquarters in Rome.
Finally, so that the control procedures can also be monitored from Pisa, a remote terminal will be built to give a local view of the control operations carried out by the NMC in Florence. Stage 2 will further develop the testing carried out in Stage 1, particularly with regard to tele-medicine and environmental monitoring, and new applications will be implemented regarding a) distributed computation for astrophysics, robotics, chemistry (in particular, molecular graphics and spectroscopy); b) tele-education on isochronous interfaces; c) remote exploitation of the nation's cultural wealth.
In a few months Siena will also have its own MAN linked to the current MAN structure and this will further enhance the regional coverage of the Tuscan MAN.