Cisco Systems Nokia Cisco Systems This document proposes updates to the current MPLS LDP and MPLS RSVP messages for LSP establishment in order to support Differentiated Services (Diff-Serv) over ATM LSRs and Frame Relay LSRs. In brief, we propose that: - a set of PHBs that requires no misordering of packets in a microflow (even if the microflow contains packets for more than one PHB) be defined as a PHB forwarding class (PFC); - packets that belong to the same PFC and the same forwarding equivalence class (FEC) should be transported over the same ATM LSP or FR LSP; - for a given FEC, a separate ATM LSP or FR LSP should be established for each PFC, so that multiple ATM or FR LSPs are established in parallel for support of Diff-Serv; - among the set of PHBs transported over the same ATM LSP or FR LSP, the different PHBs' drop precedences be mapped into, and enforced via, the layer 2 specific selective discard mechanism (CLP bit with ATM, DE bit with FR).