Updating the MPLS Label Switched Paths (LSPs) Ping Parameters IANA Registry
updates
Extracted elements (16)
The original LSP Ping registry incorrectly assumed that code points allocated by Experimental RFCs would be limited to experimental use; however, a code point in a public IANA registry is available for any document type. This, combined with an oversized experimental range, motivated the restructuring of registration procedures.
The terms 'mandatory TLV' and 'optional TLV' were dropped from RFC 8029 language because those words conflict with widespread IETF usage: RFC 8029 used them to indicate required error-response behavior, whereas other RFCs use them to indicate whether a TLV must be present in a message. The updated text describes the required action directly.
The 'Vendor Private Use' and 'Private Use' registration procedures were replaced with 'First Come First Served' because private-use code points are permitted in production networks, creating a risk that two vendors assign the same value with different meanings. If such code points were deployed in the same network, the resulting protocol conflicts would be difficult to debug.
The 'Sub-TLVs for TLV Type 9' subregistry is explicitly excluded from the updates in this document; its registration procedures remain unchanged.
Vendors that have existing implementations using Vendor Private Use or Private Use code points should register those code points under the First Come First Served procedure as soon as RFC 9041 is published, to avoid conflicts with other vendors' assignments.
An implementation that does not understand a TLV or sub-TLV with type >= 32768 (high-order bit 1) SHOULD ignore and step over it; however, an implementation MAY send an echo response with Return Code 2 as it would have for a lower-range TLV.
If an unrecognized TLV or sub-TLV comes from the upper Experimental Use range (64508-64511) or the upper FCFS range (64512-65535), the receiver may silently drop it, step over it, or send an error message; no mandatory response is required.
TLV and sub-TLV types less than 32768 (high-order bit 0) MUST either be supported by an implementation or result in a Return Code of 2 ('One or more of the TLVs was not understood') being sent in the echo response.
The high-order bit of a TLV or sub-TLV type value is the key behavioral discriminator: types 0-32767 (bit = 0) require a Return Code 2 response if unrecognized; types 32768-65535 (bit = 1) may be silently dropped if unrecognized.
The TLV and sub-TLV code point space is divided into four registration-procedure blocks per half: Standards Action, RFC Required, Experimental Use (4 code points each, reserved/not to be assigned), and First Come First Served. This structure applies uniformly to the TLVs registry and all updated sub-TLV subregistries.
Six sub-TLV subregistries (for TLV Types 1/16/21, 6, 11, 20, 23, and 27) are each updated with the same eight-range structure as the TLVs registry, replacing 'Vendor Private Use' or 'Private Use' with FCFS and adding Experimental Use ranges. The 'Sub-TLVs for TLV Type 9' subregistry is explicitly not updated.
The 'Message Types' registry under the MPLS LSP Ping Parameters namespace is updated: code point 0 reserved, 'Specification Required' changed to 'RFC Required', four code points (248-251) carved out for Experimental Use, and 252-255 relabeled 'Private Use' (not to be assigned).
The 'Reply Modes' registry is updated in parallel with Message Types: code point 0 reserved, 'Specification Required' changed to 'RFC Required', 248-251 set aside for Experimental Use, and 252-255 marked Private Use (reserved, not to be assigned).
The 'Return Codes' registry is updated: 'Specification Required' changed to 'RFC Required', four Experimental Use code points (248-251) added, and the full 36-value assignment table (codes 0-35 plus reserved ranges) is restated. Code point 0 retains its existing assignment as 'No Return Code'.
The 'TLVs' registry is restructured into eight ranges: Standards Action (0-16383 and 32768-49161), RFC Required (16384-31739 and 49162-64507), Experimental Use (31740-31743 and 64508-64511, not to be assigned), and FCFS (31744-32767 and 64512-65535). The lower four ranges require an error response if unrecognized; the upper four may be silently dropped.
This document updates only IANA registries and their terminology; it does not change how code points are used in the protocol and therefore does not introduce new threats. The clarified terminology improves security by making consistent implementations more likely and reducing ambiguity that could be exploited.