6MAN Working Group A. Petrescu
Internet-Draft CEA, LIST
Intended status: Standards Track September 21, 2018
Expires: March 25, 2019

The length of the IPv6 link-local prefix


The length of the IPv6 link-local prefix is 64 decimal.

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Table of Contents

1. Statement

The length of the IPv6 link-local prefix is 64 decimal.

The IPv6 link-local prefix is represented textually "fe80::/64".

   |    64 bits, the link-local prefix  |          64 bits           |
   |1111111010000000000000...00000000000|       interface ID         |

Figure 1: The IPv6 link-local prefix

The illustration of the IPv6 link-local prefix is:

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

prefix: a contiguous string of bits valid for forwarding operations and for subnet formation.

textual representation of a prefix: e.g. fe80::/64.

n leading bits: the first n bits in a string of bits read from left to right in a writing system that is read left-to-right. E.g. the 10 leading bits of the fe80::/64 textual representation of the IPv6 link-local prefix are 1111111010.

3. Security Considerations

The clarification of the definition of the prefix length of the IPv6 link-local prefix at IANA is: call it 'leading bits' and not 'prefix', or state that the IPv6 prefix length of link-local addresses is 10 decimal. This clarification has beneficial impact in the algorithm implementation for calculation of the opaque and stable Interface Identifiers for IPv6 link-local addresses. It also positively impacts some implementations of IPv6 forwarding.

4. IANA Considerations

IANA is requested to change the name of the column head in the table that depicts the "Internet Protocol Version 6 Address Space". The name should be "The n leading bits of an address" instead of "IPv6 Prefix".

The desired effect of this change is that the IPv6 link-local prefix be "fe80::/64" and that the 10 leading bits of this prefix be 1111111010. A second effect is that the textual representation "fe80::/10" as an IPv6 link-local prefix should disappear from that IANA page, because it is wrong.

5. Contributors

Listed from 6man WG discussion.

6. Acknowledgements

Listed from 6man WG discussion.

7. Normative References

[RFC1042] Postel, J. and J. Reynolds, "Standard for the transmission of IP datagrams over IEEE 802 networks", STD 43, RFC 1042, DOI 10.17487/RFC1042, February 1988.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.

Appendix A. ChangeLog

The changes are listed in reverse chronological order, most recent changes appearing at the top of the list.

Author's Address

Alexandre Petrescu CEA, LIST CEA Saclay Gif-sur-Yvette , Ile-de-France 91190 France Phone: +33169089223 EMail: Alexandre.Petrescu@cea.fr