VPWS (Virtual Private Wire Service)

The services offered by an operator are often multiple, such as "Triple Play" (voice, Internet, video) for the general public, but there are also services for businesses, such as the interconnection of geographically distant sites, or mobile collection offers consisting of transporting 2G and 3G traffic between base stations (antennas) and a centralized controller.

These different services use different technologies. Triple Play" services, for example, are delivered over an IP (Internet Protocol) network infrastructure, while "enterprise" or mobile collection services require the use of FR (Frame Relay), ATM (Asynchronous Transfer Mode) or TDM (Time Division Multiplexing) networks. To support all these services, an operator needs to set up several networks, entailing considerable investment and maintenance costs.

For economic reasons, we are now witnessing what is known as "multiservice" convergence on the same network infrastructure. Operators are looking to use the same network technology to support different services. Since network bandwidth is mainly consumed by packet services such as the Internet, the IP network has rapidly emerged as the "converged" network.

It is in this context that the notion of an IP-based virtual private network has emerged. The aim is to be able to take advantage of an IP packet network for IP services, while ensuring the continuity of traditional services (ATM, FR, TDM, etc.). In other words, to use an IP network as a backbone infrastructure to carry all types of traffic: this is known as a multiservice network.

PW ("Pseudowire") technology is now considered an indispensable network building block for L2VPN (Layer 2 Virtual Private Network). It enables the emulation of non-IP services between client devices over an IP/MPLS (Multi Protocol Label Switching) network. This emulation offers the advantage of perpetuating the technologies (Ethernet, ATM, TDM, FR...) implemented in the end devices, while optimizing transport costs. For operators, the use of this IP/MPLS backbone layer relieves the load on traditional networks.

To date, pseudowire has made it possible to offer customers two types of service:

• Virtual Private Wire Service (VPWS) ;

• Virtual Private LAN Service (VPLS).

With VPWS, the operator can provide the virtual equivalent of a leased line (point-to-point connectivity). With a VPLS, different sites of the same customer can share an Ethernet broadcast domain in the same way as if they were attached to an Ethernet switch. This is known as "any-to-any" connectivity.

In 2001, the Internet Engineering Task Force (IETF)...