Revision to Capability Codes Registration Procedures
draft-ietf-idr-capabilities-registry-change-09

Abstract

This document updates RFC 5492 by making a change to the registration procedures for BGP Capability Codes. Specifically, the range formerly designated "Reserved for Private Use" is divided into three new ranges, respectively designated as "First Come First Served", "Experimental Use" and "Reserved".

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Table of Contents

• 1. Introduction
• 2. Discussion
• 3. IANA Considerations
• 4. Security Considerations
• 5. Acknowledgements
• 6. References
• 6.1. Normative References
• 6.2. Informative References
• Author's Address

1. Introduction

The Border Gateway Protocol uses a mechanism called "Capability Advertisement" [RFC5492] to enable BGP peers to tell one another about their optional protocol extensions. These so-called "Capabilities" are signaled using code points called "Capability Codes".

[RFC5492] designates the range of Capability Codes 128-255 as "Reserved for Private Use". Subsequent experience has shown this to be not only useless, but actively confusing to implementors.

Accordingly, this document revises the registration procedures for the range 128-255, as follows, using the terminology defined in [RFC8126]:

• 128-238: First Come First Served
• 239-254: Experimental Use
• 255: Reserved

The procedures for the ranges 1-63 and 64-127 are unchanged, remaining "IETF Review" and "First Come First Served" respectively.

2. Discussion

The reason for providing an Experimental Use range is to preserve a range for use during early development. Although there are few practical differences between Experimental and Private Use, the change both makes it clear that code points from this space should not be used long-term or in shipping products, and reduces the consumption of the scarce Capability Code space expended for this purpose. Once classified as Experimental, it should be considered difficult to reclassify the space for some other purpose in the future.

The reason for reserving the maximum value is that it may be useful in the future if extension of the number space is needed.

Since the range 128-255 was formerly designated Private Use, implementors may have chosen to use code points within that range prior to publication of this document. For this reason, a survey was conducted beginning August 14, 2015 (version 01 of the individual draft) to find any such uses. A number were contributed and were used to seed Table 2. Of course there can be no guarantee that all uses were discovered, however the likelihood seems high that remaining uses, if any, genuinely do fall under the intended use of "Private Use" and are restricted to some special deployment, and are not in wide use. Furthermore, any remaining uses would be no worse than any other code point collision, such as occasionally occurs with code point "squatting", and could be dealt with in the same manner.

3. IANA Considerations

IANA is requested to revise the "Capability Codes" registry in the "Border Gateway Protocol (BGP) Parameters" group as follows.

Reference: [RFC5492] and this document.

Registration procedures:

IANA is requested to perform the following new allocations within the "Capability Codes" registry:

4. Security Considerations

This revision to registration procedures does not change the underlying security issues inherent in the existing [RFC5492] and [RFC4271].

5. Acknowledgements

Thanks to Alia Atlas, Bruno Decraene, Martin Djernaes, Jie Dong, Jeff Haas, Sue Hares, Acee Lindem, Thomas Mangin, and Tom Petch for review and comments.

6. References

6.1. Normative References

6.2. Informative References

Author's Address