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9. MPLS Support of Diff-Serv over LC-FR Interfaces

This section describes the specific operations required for MPLS support of Diff-Serv over label switching controlled Frame Relay (LC-FR) interfaces.

This document allows any number of L-LSPs per FEC within an MPLS Frame Relay Diff-Serv domain. E-LSPs are not supported over LC-FR interfaces.

9.1. Use of Frame Relay Traffic parameters and Traffic Management mechanisms​

The use of the Frame Relay traffic parameters as specified by ITU-T and Frame Relay-Forum or of vendor specific Frame Relay traffic management mechanisms is outside of the scope of this specification. The only requirement for compliant implementation is that the forwarding behavior experienced by a Behavior Aggregate forwarded over an L-LSP by the Frame Relay LSR MUST be compliant with the corresponding Diff-Serv PHB specifications.

Since there is only one bit (DE) for encoding the PHB drop precedence value over Frame Relay links, only two different drop precedence levels are supported in Frame Relay LSRs. Sections 4.2.3 and 4.4.3 define how the three drop precedence levels of the AFn Ordered Aggregates are mapped to these two Frame Relay drop precedence levels. This mapping is in accordance with the requirements specified in [DIFF_AF] for the case when only two drop precedence levels are supported.

9.2. LSR Implementation With LC-FR Interfaces​

A Diff-Serv capable LSR MUST support L-LSPs over LC-Frame Relay interfaces.

This specification assumes that Edge-LSRs of the FR-LSR domain use the "generic encapsulation" method as recommended in [MPLS_FR]. Operations without the "generic encapsulation" are outside the scope of this specification.