] made some changes to the terminology used for MPLS Special-Purpose Labels but did not define consistent terminology.
One thing that RFC 7274
did was to deprecate the use of the term "reserved labels" when describing a range of labels allocated from a registry maintained by IANA. The term "Reserved" in such a registry means "set aside, not to be used", but that range of labels was available for allocation according to the policies set out in that registry. The name "Special-Purpose Labels" was introduced in RFC 7274
in place of the previous term, and the abbreviation "SPL" was recommended.
At the time of writing the first draft version of this document, the IETF was in the process of allocating the very first SPLs from the Extended SPL (eSPL) range [RFC 8595
]. This document discusses and recommends terminology and abbreviations to be used when talking about and documenting Special-Purpose Labels.
This document updates RFC 3032
] and RFC 7274
] in that it changes the terminology for both Base SPLs (previously referred to simply as "Special-Purpose Labels") and Extended SPLs.
This document applies that terminology change to the relevant IANA registry and also clarifies the use of the Entropy Label Indicator (7) when immediately preceded by the Extension Label (15).
The key words "MUST
", "MUST NOT
", "SHALL NOT
", "SHOULD NOT
", "NOT RECOMMENDED
", and "OPTIONAL
" in this document are to be interpreted as described in BCP 14 [RFC 2119
] [RFC 8174
] when, and only when, they appear in all capitals, as shown here.