http://www.rfc-editor.org/rfc/rfc5143.txt
RFC 5143: Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation Service over MPLS (CEM) Encapsulation, A. Malis, J. Brayley, J. Shirron, L. Martini, S. Vogelsang2008-02-01T23:00:00-00:00This document describes a historical method for encapsulating Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Path signals for transport across packet-switched networks (PSNs). The PSNs explicitly supported by this document include MPLS and IP. Note that RFC 4842 describes the standards-track protocol for this functionality, and new implementations must use RFC 4842 rather than this document except when interoperability with older implementations is desired. This memo defines a Historic Document for the Internet community.