Revision to Capability Codes Registration Procedures
updates
- rfc-5492 — Capabilities Advertisement with BGP-4
Extracted elements (7)
A survey was conducted beginning August 14, 2015 to discover existing uses of code points in the formerly 'Private Use' range 128-255 before reclassifying them. Discovered uses were registered as deprecated entries to avoid collision; any undiscovered remaining uses are considered no worse than typical code point squatting.
Code point 255 (the maximum value) is Reserved rather than allocated, because it may be useful in the future if extension of the Capability Codes number space is needed.
The 'Private Use' designation for codes 128-255 was found to be useless and actively confusing to implementors. Splitting it into FCFS, Experimental Use, and Reserved ranges clarifies intent: FCFS enables orderly allocation, Experimental Use signals that code points should not be used long-term or in shipping products, and Reserved preserves the maximum value for potential future number-space extension.
Implementors may have chosen to use code points in the range 128-255 under the former 'Private Use' designation prior to RFC 8810. Such uses are no worse than any other code point collision and can be dealt with in the same manner as code point squatting; the survey-identified prestandard uses have been formally registered as deprecated.
RFC 8810 allocates seven specific code points within the newly defined FCFS range (128-238) to document prestandard/deprecated uses discovered via a survey: 128 (Prestandard Route Refresh), 129 (Prestandard Outbound Route Filtering/Routing Policy Distribution), 130 (Prestandard Outbound Route Filtering), 131 (Prestandard Multisession), 184 (Prestandard FQDN), 185 (Prestandard OPERATIONAL message), and 255 (Reserved).
RFC 8810 revises the IANA 'Capability Codes' registry registration procedures for the range 128-255, splitting the former 'Private Use' designation into: 128-238 (First Come First Served), 239-254 (Experimental Use), and 255 (Reserved). Ranges 1-63 (IETF Review) and 64-127 (First Come First Served) are unchanged, making the full FCFS range 64-238.
The revision to Capability Codes registration procedures does not change the underlying security issues inherent in the existing BGP Capabilities Advertisement (RFC 5492) and BGP-4 (RFC 4271) specifications.