Re: is source address binding more valuable for IPv6?

[Ivan Shmakov <oneingray@gmail.com>]

>>>>> Bill Cerveny <debian-v6@21st-century-networks.com> writes:

[...]

 > I'm less familiar with Teredo,

	IIUC, the same considerations apply to Teredo as well.

 > but there is a 6to4 scenario where an IPv4-based 6to4 host wants to
 > access a native IPv6 host.  In this scenario, the two hosts must
 > communicate via a 6to4 "relay" that handles
 > encapsulation/unencapsulation between 6to4 encapsulated IPv6 and
 > native IPv6.

	Actually, the 6to4 to IPv6 route and the reverse one may be
	different.  See below.

 > Dependent upon on how "close" routing-wise the 6to4 relay is both
 > hosts, it is possible for the routes taken between the two hosts to
 > be very inoptimal and asymmetric.

	So, it may be beneficial for the IPv4 + IPv6 gateways to always
	be configured for 6to4.  With the route having a more specific
	prefix (/16) than that to the IPv6 provider (tunnel broker; /3),
	it will take precedence over the native IPv6 route for 6to4
	destinations.  (The implied 6to4 network doesn't have to be
	used, except for the gateway, of course.)

	When routing the packets the other way (6to4 to native IPv6),
	only the explicit routing will help, though.

 > If both end-points are IPv4 hosts with 6to4 encapsulated IPv6, then
 > yes, the route taken can be as optimal as the IPv4 route.

	Or both of the routes, to be precise.

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