RFC 5462

Multiprotocol Label Switching (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic Class" Field, February 2009

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RFC 3032, RFC 3270, RFC 3272, RFC 3443, RFC 3469, RFC 3564, RFC 3985, RFC 4182, RFC 4364, RFC 4379, RFC 4448, RFC 4761, RFC 5129
L. Andersson
R. Asati
mpls (rtg)

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DOI:  https://doi.org/10.17487/RFC5462

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The early Multiprotocol Label Switching (MPLS) documents defined the form of the MPLS label stack entry. This includes a three-bit field called the "EXP field". The exact use of this field was not defined by these documents, except to state that it was to be "reserved for experimental use".

Although the intended use of the EXP field was as a "Class of Service" (CoS) field, it was not named a CoS field by these early documents because the use of such a CoS field was not considered to be sufficiently defined. Today a number of standards documents define its usage as a CoS field.

To avoid misunderstanding about how this field may be used, it has become increasingly necessary to rename this field. This document changes the name of the field to the "Traffic Class field" ("TC field"). In doing so, it also updates documents that define the current use of the EXP field. [STANDARDS-TRACK]

For the definition of Status, see RFC 2026.

For the definition of Stream, see RFC 8729.

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