Subject: [Mip4] [Issue] draft-kulkarni-mobileip-dynamic-assignment: Routing concerns

From: Henrik Levkowetz <[email-masked]>
Date: Sat, 30 Aug 2003 12:44:18 +0200

Hi,

	One concern I've had with this draft is the change in routing.
In MIPv4, prior to this, RRQ and RRP has always travelled back and
forth between the same two end nodes, while here we introduce a change
where a different node than the HA originally addressed by the MN may
be answering. Pete has already pointed out 3 issues with this:
	a) It removes the possibility to do ingress filtering of 
	RRPs, which widens the possibility of DOS attacks by forging
	rejections
	b) It seems not to work with co-located CoA registration through
	FA
	c) It raises the possibility of routing loops amongst HA's

I'd like to add yet another one:
	d) It seems to me that it also breaks the NAT traversal mechanism,
	which is rather crucial to a large part of the deployment scenarios
	we are currently seeing. The port on the NAT from which the
	original request was issued is lost through the forwarding, and if
	the Directed HA overwrites the source address, the detection of
	the NAT is also made impossible. (Actually, if the Directed HA
	overwrites the source address, an Assigned HA with NAT traversal
	support would identify the Directed HA as a NAT)

For these reasons, I think it would be much better to have a solution
where the first (Directed) HA returns an error reply and and indication
of the next HA to contact to the MN. This would remove all the objections
above, admittedly with the loss of some efficiency, but correct operation
has to come before efficiency, as I see it.

	Henrik