PSEUDO WIRE EMULATION EDGE-TO-EDGE

PSEUDO WIRE EMULATION EDGE-TO-EDGE

ABSTRACT:

Pseudo Wire Emulation Edge-to-Edge (PWE3) is a mechanism that emulates the essential attributes of a service over a PSN. As the term ‘emulation’ implies PWE3 is an emulation of the actual (native) services, which include Frame Relay, Asynchronous Transfer Mode (ATM), Ethernet T1, and SONET (Synchronous Optical Network). All these are implemented over packet switched networks (PSNs) using IP or MPLS.
Service provider usually deliver multiple services, and typically would employ a network composed of parallel or "overlay" networks, with each of those networks implementing a specific service viz. voice, Internet access, Frame Relay etc. From the capital expense as well as operational costs viewpoints, a converged network is a viable solution. PWE3 offers an elegant means to enjoy the benefits of a new packet-based infrastructure, while leveraging the existing base of SONET gear. Thus, evolves the emulation of circuits or services via pseudo wires (PWs).
The PSN can transport Protocol Datagram Units (PDUs) for multiple services, and the conversion / interworking functions per service pair are not needed. The tunnels used in this approach are referred to ‘pseudo wires’ in the metaphorical sense of wire, as ‘on the wire’ packet formats. PWE3 is a single transport type operating over a common packet-switched network (PSN) service model.
The required functions of PWs include encapsulating service-specific bit-streams or PDUs arriving at an ingress port, and carrying them across a path or tunnel, managing their timing and order, and any other operations required to emulate the behavior and characteristics of the service as faithfully as possible. Tunnels for PWE3 encapsulations will use IP (both versions), Layer Two Tunneling Protocol (L2TP) or Multiprotocol Label Switching (MPLS). Pseudo wires require the edge devices providing service interfaces to use common service-specific techniques for encapsulating PDUs and maintaining the service characteristics and behavior in the data flow. PWE3 does not force control on the underlying PSN, but only function at the endpoints of the pseudo wire. A pseudo-wire (PW) is a connection between two provider edge (PE) devices which connects two pseudo-wire end-services (PWESs) of the same type. A PWES is a link between a customer edge (CE) device and a PE device.


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