Subject: draft-ietf-zeroconf-ipv4-linklocal-04.txt incompatibility issues

From: Bernard Aboba <[email-masked]>
Date: Mon, 13 Aug 2001 08:27:17 -0700 (PDT)

In section 2 of draft-ietf-zeroconf-ipv4-linklocal-04.txt it states:

"Windows and Mac OS hosts that already implement IPv4 address
auto-configuration are compatible with the rules presented in this
section."

This statement would appear to indicate that systems
implementing this draft will be able to interoperate with existing
(non-standard) implementations. 

This is not the case. 

Systems implementing draft-ietf-zeroconf-ipv4-linklocal-04.txt will *not*
interoperate with existing implementations, creating "islands" of
linklocal interoperability. IMHO, this is a bad thing.  

The problem is that TTL=255 must be set on packets sent from the linklocal
address. Packets with lower TTLs will be silently discarded on reception.
During WG last call, we discussed alternatives to this, such as 
restriction on addressing modes. I believe that these alternatives are
preferrable to requiring TTL=255 for all linklocal traffic.

Windows 98, 98SE, ME, Windows 2000 and XP systems set TTL=128
by default on outgoing packets sent to 169.254/16.