Using /126 for IPv6 router links

Mon Jan 25 02:21:51 UTC 2010

> During the days of the IPng directorate, quite a number of different alternatives were considered.  At one point, there was a compromise proposal known as the "Big 10" design, because it was propounded at the Big Ten Conference Center near O'Hare.  One feature of it was addresses of length 64, 128, 192, or 256 bits, determined by the high-order two bits.  That deal fell apart for reasons I no longer remember; SIPP was the heir apparent at that point.  Scott and I pushed back, saying that 64 bits was too few to allow for both growth and for innovative uses of the address.  We offered 128 bits as a compromise; it was accepted, albeit grudgingly.  The stateless autoconfig design came later.
>
>                --Steve Bellovin, http://www.cs.columbia.edu/~smb

This historical record finally made me understand why we have up to
/128 prefixes with /128 addresses instead of what would suit best
stateless autoconfig: up to /64 prefixes with /128 addresses.

Rubens