IID length text [was Re: Review of draft-ietf-6man-rfc4291bis-06]

[Brian E Carpenter <[e-mail]>]

A modest suggestion:

OLD
   For all unicast addresses, except those that start with the binary
   value 000, Interface IDs are required to be 64 bits long.  Background
   on the 64 bit boundary in IPv6 addresses can be found in [RFC7421].

NEW
   IPv6 routing is based on prefixes of any valid length up to 128 [BCP198].
   For example, [RFC6164] standardises 127 bit  prefixes on point-to-point
   links. However, consistent use of Stateless Address Autoconfiguration
   (SLAAC)[RFC4862] requires that all interfaces on a link use the same length
   of Interface ID. In practice, this means that to guarantee interoperability
   of SLAAC, a fixed length of Interface ID is necessary. For all currently
   allocated unicast addresses, except those that start with the binary
   value 000, that length is 64 bits. Note that this value is an arbitrary
   choice and might be changed for some future allocation of unicast address
   space. Background on the 64 bit boundary in IPv6 addresses can be found
   in [RFC7421].

Regards
   Brian