Subject: [LL10] Add warnings to applicability statement

From: Erik Guttman <[email-masked]>
Date: Thu, 13 Feb 2003 11:16:12 +0100 (CET)

[WG chair hat off]
I reject the rewording as stated, as it is too restrictive.

The applicability of v4LL should not be predicated on the 
least functional of *all* applications  run on a host.  It may
be the case that some applications do break.  Users will 
potentially have to get new versions one day to support both
local and global use, and their transitions.  I understand
that this view is not shared, but it is my view.  It is OK
to break some applications when introducing new functionality.

Microsoft has shown that it is possible to introduce new 
versions of network applications which can be resilient to address 
renumbering events.

I accept the revised text from Philip Nye as modified by
Keith Moore.  (I gathered it up without changing it, I hope.
The postings on this issue got a little confusing.  Anyway,
I agree with the text below.)

   IPv4 link-local addresses and their dynamic configuration have
   profound implications upon applications which use them. This is
   discussed in Section 7. Many applications fundamentally assume
   that addresses of communicating peers are routable, relatively
   unchanging and unique. These assumptions no longer hold with IPv4
   link-local addresses, or a mixture of link-local and routable 
   addresses.  Therefore while many applications will work properly 
   with LL addresses, or a mixture of LL and routable addresses, 
   others may do so only after modification, or will exhibit reduced 
   or partial functionality.  

   In some cases it may be infeasible for  the application to be 
   modified to operate under such conditions.

   IPv4 link-local addresses should therefore only be used where 
   stable, routable addresses are not available (such as on ad hoc 
   or isolated networks) or in controlled situations where these 
   limitations and their impact on applications are understood and 
   accepted.

Erik