ical 64 ports STM 1 native SFP elect. Electrical 32 ports STM 1 ATM SFP elect. Electrical 32 ports STM 1 POS SFP elect. Electrical 32 ports STM1, STM 4 native Gray optics 32 ports STM1, STM 4 ATM Gray optics 32 ports STM1, STM 4 POS Gray optics 32 ports STM-16 native Gray optical 32 ports STM-16 ATM Gray optical 32 ports STM-16 POS Gray optical 32 ports STM-64 native Gray optical 9 ports STM-64 POS Gray optical 9 ports Fast Ethernet SFP elect. Electrical 32 ports Fast Ethernet Gray optical 32 ports Gray optical 32 ports 10 GbE Gray optical 4 ports Switching Systems: Architecture and Performances justifies the presence of a software feature allowing the consolidation at layer 3 signals coming from the mobile network. These layer 2 capabilities also reflect in the availability of a wide variety of interfaces supporting all the aforementioned formats. On the core side, full MPLS functionality is supported to interface with MPLS net- works, in this case the BRAS can also work as label edge router, being the origin and sink of the LSPs. 7.9 Packet Switching at Ethernet Layer: Carrier Class Ethernet Switches In Chapter 3 we have seen that the main role of switching machines in the metro core area is to aggregate the signals coming from the access and deliver them to the point of pres- ence where the AAA functions are performed. Such aggregation is performed either with TDM machines like MSPP or using carrier Ethernet switches, a solution that is attracting more and more the attention of the main carriers, especially in Europe [83]. In Section 3.2.3 we have described the principle on which the carrier class Ethernet is based. In particular we have seen that the metro Ethernet forum standards base the working of carrier class Ethernet on the concept of backbone VLAN, to which a particular VLAN identifier is associated to distinguish it from the private VLAN that a real LAN network can define. In particular, when an Ethernet frame is received from an edge public switch or from an edge switch/router, it is enveloped within