Figure 1 provides an example of an Ethernet interworking VLL. The Ethernet interworking VLL provides a point-to-point Ethernet VLL service between Frame Relay (FR) attached users, ATM-attached users, and Ethernet-attached users across an IP/MPLS packet switched network. It effectively provides ATM and FR bridged encapsulation termination on the existing Epipe service of the 7750 SR.
The following connectivity scenarios are supported:
a Frame Relay or ATM user connected to a ATM network communicating with a Ethernet user connected to a 7750 SR PE node on a IP/MPLS network
a Frame Relay or ATM user connected to 7750 SR PE node communicating with an Ethernet user connected to a 7750 SR PE node on a IP/MPLS network. This feature supports local cross-connecting when these users are attached to the same 7750 SR PE node.
Users attach over an ATM UNI with RFC 2684, Multiprotocol Encapsulation over ATM Adaptation Layer 5, tagged/untagged bridged Ethernet PDUs, a FR UNI using RFC 2427, Multiprotocol Interconnect over Frame Relay, tagged/untagged bridged Ethernet PDUs, or an Ethernet tagged/untagged UNI interface. However, the VCI/VPI and the data-link connection identifier (DLCI) are the identifiers of the SAP in the case of ATM and FR, respectively, and the received tags are transparent to the service, so are preserved.
The Ethernet pseudowire is established using T-LDP signaling and can use the ether or vlan VC types on the SDP. The SDP can be either an MPLS or GRE type.