http://www.rfc-editor.org/rfc/rfc5331.txt
RFC 5331: MPLS Upstream Label Assignment and Context-Specific Label Space, R. Aggarwal, Y. Rekhter, E. Rosen2008-08-01T23:00:00-00:00RFC 3031 limits the MPLS architecture to downstream-assigned MPLS labels. This document introduces the notion of upstream-assigned MPLS labels. It describes the procedures for upstream MPLS label assignment and introduces the concept of a "Context-Specific Label Space". [STANDARDS-TRACK]