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RFC 5952, "A Recommendation for IPv6 Address Text Representation", August 2010

Source of RFC: 6man (int)

Errata ID: 2656
Status: Rejected
Type: Technical

Reported By: D. Stussy
Date Reported: 2010-12-02
Rejected by: Brian Haberman
Date Rejected: 2012-05-30

Section 4.3 says:

4.3.  Lowercase

   The characters "a", "b", "c", "d", "e", and "f" in an IPv6 address
   MUST be represented in lowercase.

It should say:

4.3.  Case of Alphabetic Digits.

   The digits "A" through "F" in an IPv6 address
   MUST be represented in upper case.  User and user
   derived input may be represented using lower case.


Historically from the 1960's, hexidecimal digits other than decimal digits are represented by upper case letters. Lower case letters may have become acceptable as user input, but such resulted from lazy programmers who couldn't manage to hit the shift key on their keyboards. However, lower case is not acceptable for digit output. Many early assemblers would not even accept lower case as valid input digits except where the radix base exceeded 36 (thus exhausting all upper case values). This poor programming practice should not be allowed to be codified into any Internet standard.

- Struble, George W., "Assembler Language Programming: The IBM System/360 and /370." Addison-Wesley Publishing Co., 1969 and 1975 (Second Edition), Page 6. ISBN 0-201-7322-6
- Barden, William Jr., "TRS-80 Assembly-Language Programming." Tandy Corporation, 1979, page 14. Library of Congress #79-63607
- Leventhal, Lance A., "6502 Assembly Language Programming." Osborne McGraw-Hill, 1979 and 1986 (Second Edition), Page 1-4. ISBN 0-07-881216-X
- Intel Corporation, "Intel486 Microprocessor Family Programmer's Reference Manual." 1995, Page 1-8 (Section 1.3.4). No ISBN or LoC #.
- Cress, Paul, Dirksen, Paul, and Grahm, J. Wesley, "Fortran IV with WatFor and WatFiv." Prentice-Hall, 1968 and 1970, Page 245. LoC 74-129241
- Mano, M. Morris, "Computer System Architecture." Prentice-Hall, 1982, Page 79. ISBN 0-13-166611-8
- Higgins, Richard J., "Electronics with Digital and Analog Integrated Circuits." Prentice-Hall, 1983, Page 60. ISBN 0-13-250704-8

However, I also note this ONE source permits mixed case:
- Kernighan, Brian W. & Ritchie, Dennis M., "The C Programming Language", Prentice Hall, 1978 (First Edition), Page 180. ISBN 0-13-110163-3

Many other pre-1990 computer science and engineering books show hexidecimal non-decimal digits as upper case only and NEVER as lower case. However, I could not find pages in them defining the lettered-digits as upper case only despite their consistent usage of upper case printing.
This errata is attempting to overturn the clear consensus of the WG.

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