acket loss, and this must be compensated when delivering TDM over Ethernet. All these issues are addressed in the pseudowire standards applicable to carrier class Ethernet, and present days' carrier Ethernet switch can transport SDH/SONET signals SO to allow legacy equipment to be integrated into the new metro network. 7.9.2 Architecture of a Carrier Class Ethernet Switch From an architectural point of view, many issues relative to router design are replicated if carrier Ethernet switches design is considered. From a functional point of view, the architecture of an Ethernet switch is based on dis- tributed intelligence exactly like that of a backbone router. Received frames are stored in a memory resident in the line card, after that the forward- ing is performed in two steps: first the B-VLAN ID and the MAC address are read and sent to the forwarding processor. This processor first looks at the B-VLAN ID to identify the forwarding plane to which the considered frame belongs, then access the MAC addressing table using the MAC of the incoming frame to determine the address of the output port. Generally, the B-VLAN assignment can be done via software, since the maximum num- ber of possible B-VLAN is limited to 4096. On the contrary, the MAC address table is generally implemented via a CAM to speed the frames forwarding. References 1. Chao, H. J., Liu, B., High Performance Switches and Routers, Wiley-IEEE Press, Hoboken, NJ, s.l., 2007, ISBN-13: 978-0470053676. 2. Law, K. L. E., Leon-Garcia, A., A large scalable ATM multicast switch, IEEE Journal on Selected Areas in Communications, vol 5, num 3, 1997, pgs. 844-854. 3. Gebali, F., Analysis of Computer and Communication Networks, Springer, New York, s.l., 2008, ISBN: 9780387744377. 4. Kabacióski, W., Nonblocking Electronic and Photonic Switching Fabrics, Springer, New York, s.l., 2005, ISBN: 038725435. Telecommunication Networks 5. Hsu, L.-H., Lin, C.-K., Graph Theory and Interconnection Networks, CRC Press, Boca Raton, FL, s.l., 2008, ISBN-13: 978-1420044812. 6. Kat