cessors and the central processor located in the central control card. The switch fabric is contained in a single double slot unit and has a capacity of 40 Gbit/s. The software features, however, are quite articulated both on the client interface and on the line interface. On the client side, since the BRAS has to interface with DSLAMs, it can accept and pro- cess at layer 2 both native Ethernet and ATM. This is so, because several DSLAMs are still ATM based and this situation will last for a long time. Moreover, several business customers still use ATM and frame relay [30], both to guar- antee a greater security (in case of customers like banks) and simply to use existing equip- ment. Thus, the BRAS has to manage also frame relay. Last, but not least, several customers are simply connected to the network at layer 2 via PPP; thus, also PPP has to be supported in all its flavors, depending on the protocol stack: as a matter of fact, we have IP/PPP, ATM/PPP, Frame Relay/PPP [30]. In the view of a convergent network, also signals coming from the mobile network can be consolidated via the BRAS to be transported through the network infrastructure. This Switching Systems: Architecture and Performances TABLE 7.7 Summary of the Feature List of a Practical Gigabit Core Router Core Gigabit Router Platform Mechanic ETSI 300 119 rack 12 unit per sub-rack 2 sub-racks per rack 1 sub-rack for the switch fabric and the processors Platform redundancy Power-feed redundancy 1:1 Fan redundancy 1:4 (1 redundant fan out of 4 working) Fan-controller redundancy 1:1 Sub-rack control card redundancy 1:1 Fabric-card redundancy 1:5 (1 card redundant out of the 4 working) Backplane 1 GbE electrical bus using advanced PCI protocol Control Duplicated network element controller in hot mirroring configuration Management and Configuration SMNP support SNMPv1 SNMPv2c SNMPv3 IP protocol suite Full support for IPv4 and IPv6 MPLS capability Full MPLS protocol suite GMPLS capability GMPLS protocol suite with UNI interface toward transport layer networ