MPLS-TP – The new technology for packet transport networks

Abstract

The Internet Engineering Task Force (IETF) and the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T) have undertaken a joint effort to standardize a new transport profile for the multi-protocol label switching (MPLS) technology that is intended to provide the basis for the next generation packet transport network. The fundamental idea of this activity is to extend MPLS where necessary with Operations, Administration and Maintenance (OAM) tools that are widely applied in existing transport network technologies such as SONET/SDH or OTN. This paper provides a brief history of the MPLS-TP standardization activities and addresses the MPLS-TP OAM functions. These functions are targeted at making MPLS comparable to SONET/SDH and OTN in terms of reliability and monitoring capabilities, i.e., MPLS-TP will become a true carrier grade packet transport technology. An MPLS-TP network can be operated in an SDH-like fashion and a network management system (NMS) can be used to configure connections. Connection management and restoration functions, however, can alternatively be provided utilizing the Generalized MPLS (GMPLS) control plane protocols which are also applicable to the MPLS-TP data plane. In addition to the simplification of the network operation leading to reduced operational expenditures (OPEX), the GMPLS control plane provides network restoration capabilities in addition to the network protection features that the MPLS-TP data plane already provides; this results in a further improved network resiliency. The MPLS-TP technology is also multi-service capable leveraging the pseudo-wire technology that has been developed at the IETF and which is still evolving. Some applications require synchronization, e.g. mobile services and interconnection of telephony switches. Ethernet is an asynchronous network protocol and hence protocol extensions are necessary. This paper discusses the different emerging standards. One of the key requirements is that the new MPLS-TP network layer must be capable to utilize the existing physical infrastructure and the paper lists the various adaptation or encapsulation techniques that allow MPLS-TP packets to be carried over a variety of different physical technologies ranging from SONET/SDH and OTN to Gigabit Ethernet.