PWE3 stands for Pseudo-Wire Emulation Edge to Edge, which is a technology that allows different types of Layer 2 services, such as Ethernet, ATM, TDM, or SONET/SDH, to be transported over a packet-switched network (PSN), such as MPLS, IP, or L2TPv3. PWE3 creates a virtual connection, called a pseudowire (PW), between two provider edge (PE) routers that emulates the behavior and characteristics of the original service.
Some examples of PWE3 are:
• TDM PW: This is a method for carrying time-division multiplexed (TDM) circuits, such as E1, T1, E3, or T3, over a PSN. It enables enterprises to run voice, video, and legacy data over the PSN, and service providers to offer leased and private lines over the PSNl.
• ATM PW: This is a transparent cell transport service that allows migration of ATM services to a PSN without having to reconfigure the ATM subscriber or customer edge (CE) devices. It is used as an internal function in an ATM service provider’s network to connect existing ATM switches via a higher-speed PSN, or to provide ATM backhaul services for remote access to existing ATM networks.
• PW-to-TE Tunnel Mapping: This is a technique that permits operation of PW services across MPLS PSNs by mapping PWs to MPLS traffic engineering (TE) tunnels. This can improve the performance and reliability of PWs by using the TE features of MPLS, such as bandwidth reservation, fast reroute, and path optimization.
Some practical use-cases of PWE3 are:
• Network convergence: PWE3 can help network operators to converge their multiple services onto a single IP backbone network, reducing the cost and complexity of network management and maintenance. PWE3 can also enable seamless interworking between different types of services and networks.
• Service migration: PWE3 can facilitate the migration of legacy services to new technologies without disrupting the existing customers or applications. PWE3 can also provide backward compatibility and interoperability for legacy devices and protocols.
• Service innovation: PWE3 can enable new types of services that combine the advantages of both Layer 2 and Layer 3 technologies, such as Ethernet VPNs, IP VPNs over Ethernet, and Layer 2 multicast.