Subject: RE: draft-ipngwg-default-addr-select-00.txt

From: Tim Hartrick <[email-masked]>
Date: Mon, 25 Oct 1999 16:41:38 -0700 (PDT)

Richard,

	One scenario which I have run into recently would be not work
properly if this restriction held.  Now it may be an unrealistic scenario
or an implementation specific scenario but here goes.

	We have an IPv6 node that has a Ethernet link which has a globally
routable IPv6 address assigned to it.  For the moment lets assume that it
was statically assigned.  There are no IPv6 routers on the Ethernet.

	The node also has a IPv6 in IPv4 tunnel interface configured such
that it has a default route pointing to a an IPv4 compatible IPv6 address
that resides on the other end of the tunnel.  This tunnel is the node's
connection point to the 6bone.

	Now the node wants to start a TCP connection to some node on the
6bone.  Using your restriction it wouldn't have an appropriately scoped
address to use for the communication even though it has a perfectly good
address hanging off the Ethernet interface.

	I believe this scenerio is somewhat akin to the unnumbered interface
scenario to which KRE was alluding.

	Now one can easily say that the tunnel interface should have been
assigned the globally routable address in the first place.  Because of the
way our implementation currently handles tunneling that wasn't an option.
It may be that the answer is to simply make tunnel interfaces "first-class"
interfaces and this scenario will go away.  I suspect that with 6[to|over]4
that is going to be essential anyway.

Tim Hartrick
Mentat Inc.
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