Benchmarking Performance Characteristics for Delivering Ethernet Private Line Service in a Multi-vendor SONET Environment

Ethernet-based services continue to grow in popularity as customers use the technology for wide area network connectivity. Initially, service providers deployed switched Ethernet network overlays_also called Ethernet over fiber_to meet customer demand. However, this approach is costly and is difficult to manage, and so does not scale well. Verizon has recognized the need to leverage its existing transport infrastructure and has developed a comprehensive approach that uses existing legacy SONET and NG-SONET equipment to deliver an Ethernet private line (EPL) service. EPL service allows Enterprise LANs to extend beyond their metropolitan boundaries providing a less expensive and more efficient alternative than DS3 for WAN connections to customer sites.Ethernet Private Line service focuses primarily on Layer 1 transport of Ethernet, Fast Ethernet and Gigabit Ethernet at 10 Mbps, 100 Mbps, and 1 Gbps respectively; the transport network element is transparent to Layer 2. Verizon has worked extensively with all of its major SONET equipment vendors to develop platforms that support this type of undertaking. The current challenge is to establish and maintain EPL performance characteristics in a multi-vendor NG-SONET environment.Verizon's implementation of Ethernet over SONET (EoS) is based on the generic framing procedure (GFP) and virtual concatenation (VC) standards developed by the ITU-T[1]. GFP functions as an encapsulation envelope for adapting multiple packet-based client protocols to SONET/SDH network infrastructures. Once encapsulated, client signals can be transported over existing SONET facilities in a bandwidth-efficient manner and can make use of the embedded operations, administration, and maintenance (OA&M) features. Verizon's implementation of VC allows for transport flexibility by mapping the client signals into high order STS-1 containers where an arbitrary number of standard containers can be combined and diversely routed through its SONET network.Similar to existing TDM-based private line services, Verizon's customers expect EPL to perform with all the transmission characteristics of a SONET network. However, Verizon has discovered that its NG-SONET vendors are using different options in the GFP and VC specifications, causing a mismatch of transmission speeds at the customer ingress and egress points. This leads to customer confusion and makes it difficult for Verizon to guarantee service because it cannot predict how the circuit will perform at both ends. In addition, its customers require circuit performance data so they can perform layer-2 functions of rate shaping and policing.Addressing the Challenge:Today, Verizon works around the issue of GFP/VC implementation incompatibility by using equipment by the same vendor on both ends of the circuit. However, the goal is to define a set of standard EPL service attributes that can be used to benchmark Ethernet and NG-SONET performance in a multi-vendor EoS environment. Examples of EPL attributes being benchmarked by Verizon include user-network interface (UNI), Committed Information Rate (CIR), Committed Burst Size (CBS), Ethernet Virtual Circuit (EVC), and Latency.[1] "Generic framing procedure (GFP)", ITU-T recommendation G.7041/Y.1303, January 2005"Virtual concatenation of PDH signals", ITU-T recommendation G.7043/Y.1343, July 2004