The role of pseudo-wires for layer 2 services in intelligent transport networks

Abstract

Pseudo-wire emulation edge-to-edge over multiprotocol label switching (MPLS) is a promising technology for layer 2 transparent service support in metro networks. It supports Ethernet private line applications such as virtual private wire services (VPWS), multipoint local area network (LAN) applications such as virtual private LAN services (VPLS), frame relay, asynchronous transfer mode (ATM), and even the emulation of time division multiplexing (TDM) services. In the case of Ethernet, this technology circumvents the disadvantages of native Ethernet-based services, such as the need for spanning trees. In combination with traffic engineered label-switched paths (LSPs), it promises support for quality of service (QoS) differentiation and traffic engineering for high-value business services. MPLS is currently viewed as the technology that could satisfy this need, but because it serves so many other purposes as well, it entails complex control plane protocols and relatively high cost. This is in opposition to operator demand for low capital expenditure (CAPEX) and operational expenditure (OPEX) cost when introducing new services. This paper presents an analysis of how TDM-based transport networks can evolve, maximizing the benefit of established transport technologies, while supporting existing layer 2 transport services as well as new services such as Internet Protocol television (IPTV) and video on demand. The paper identifies which of the mechanisms that are underlying MPLS-based pseudo-wire services are truly essential, and which could be implemented by other means and thus offer new possibilities for migration and convergence. Besides conceptual considerations, the network efficiency of alternative implementation options is analyzed and compared. © 2007 Alcatel-Lucent.