sion bandwidth, different segments of a LAN and to suitably route the Ethernet frames. These differences also correspond to a major difference in the routing and forwarding engines of routers and switches, which will be detailed in Chapter 7, and that are caused by the fact that while an Ethernet domain is a limited network with a limited number of MAC addresses, the worldwide IP network has a huge number of IP addresses that cannot be managed by a single forwarding table forcing to adopt a forwarding policy based on prefixes and not on complete addresses. Due to its effectiveness, the Ethernet is today practically the only layer 2 protocol used in LANs. Since a huge quantity of data is produced in the Ethernet format and since the volumes of Ethernet subsystems is SO high that prices are relatively low with respect to other subsys- tems used in public network equipment, it is quite natural to try to understand if Ethernet can be used at layer 2 (e.g., in between the Internet layer and the optical transport) in the public network also. For sure this cannot be done without somehow adapting the LAN-oriented protocol, since it cannot be scaled to the public network dimensions and does not provide all the monitor capabilities that a carrier needs to support its services. Recognizing this, the IEEE and successively a new industrial group called Metro Ethernet Forum (MEF) started to elaborate new Ethernet standards that are suitable for use in a wide area, public network, thus creating the Carrier Class Ethernet technology [31,32]. Requirements of this Ethernet evolution are as follows: Presence of functional support for a network management with complete capability Scalability to the public network scale Carrier level resilience Capability of assuring QoS to support services with SLA Capability of being integrated with legacy transport machines 3.2.4.1 Protocols to Support Management Functionalities Even if all management functionalities are in principle requested, a few functionalities are the key to present a carrie