This document describes MPLS-TP Shared Ring Protection (MSRP), an 
extension to MPLS-TP. It doesn't need any more or less security than 
MPLS-TE itself. The  Security Considerations say:

    The RPS protocol defined in this document is carried in the G-ACh
    [RFC5586], which is a generalization of the Associated Channel
    defined in [RFC4385].  The security considerations specified in 
these
    documents apply to the proposed RPS mechanism.

That seems sufficient for this document.

--Paul Hoffman