r that is independent of the underlying delivery mechanism. Ethernet Service Framework In its simplest form the reference model of a Metro Ethernet Network (MEN) is as illustrated in Figure 14.1. A detailed description of the MEF architecture can be found in MEF 4 (2004). It has two major components: the Customer (or subscriber) Edge (CE) equipment and the MEN trans- port network. The physical demarcation between these components is the User Network Interface (UNI). The service model that uses this architecture is described in terms of what is visible at the CE. The advantage of such an approach is that the internal structure and technologies used inside the MEN are not visible to the customer. As such the delivery of Ethernet services may be provided in the MEN in a number of way, including Over Ethernet itself, according to the 802.1 and 802.3 standards of the IEEE. Over access technologies that may be fiber or copper based. By mapping the Ethernet frames into SDH or PDH using Generic Framing Procedure (GFP) to provide point-to-point private line-type services (Van Helvoort, 2005; ITU-T G.7041, 2005b). By transporting Ethernet across an IP/MPLS network (Hussain, 2006). This can be used to provide a point-to-point Virtual Private Wire Service (VPWS) or LAN emulation in the form of a Virtual Private LAN Service (VPLS). In both cases the customers' Ethernet frames are encapsulated with one or more MPLS headers at a provider edge device that faces the CE; they are then transported to another provider edge device that de-encapsulates the frames and passes them onto another CE. The set of UNI reference points that form an association for the purpose of supporting a service is referred to as an Ethernet Virtual Connection. An EVC can be thought of as a layer-2 virtual private network. Some examples of EVCs are illustrated in Figure 14.2. The association formed by an EVC may be a simple point-to-point relationship consist- ing of two UNIs where traffic from the ingress UNI is delivered to the egress UNI. Alterna- tivel