Juniper Networks Trinity College This document describes a way to apply opportunistic security between adjacent nodes on an MPLS Label Switched Path (LSP) or between end points of an LSP. It explains how keys may be agreed to enable encryption, and how key identifiers are exchanged in encrypted MPLS packets. Finally, this document describes the applicability of this approach to opportunistic security in MPLS networks with an indication of the level of improved security as well as the continued vulnerabilities. This document does not describe security for MPLS control plane protocols.