Subject: draft-hain-ipv6-rpf-icmp-00.txt

From: Arifumi Matsumoto <[email-masked]>
Date: Mon, 1 Nov 2010 11:21:53 +0900

Tony,
thank you for your draft.

IIRC, now that the address selection design team reached conclusion, 
the 6man chairs have decided that the next step is to start discussion at 6man ML, 
and to compare each solution for the address selection problems.
I think this is a good start to look at Tony draft of ICMP error based address selection
mechanism.

Regarding the mechanism itself, I find a lot of resemblance with the proposals
discussed before:
http://tools.ietf.org/html/draft-matsuoka-multihoming-try-and-error-00

So, some parts of the analysis of section 3.3 can be applied to this proposal, too.
http://tools.ietf.org/html/draft-ietf-6man-addr-select-sol-03#section-3.3

Other than that, several issues occurred to me.

- the destination address of the ICMP error message.
 ISP's PE perform this rpf check and it may try to send an ICMP error message.
 But, if the source address is not on the routing table, or the route to the
 source address is not the path from which the packet comes from, the PE router
 cannot/may not send an ICMP error message.

 So, it will restrict the use-case to something like a home network attached
 to multiple ISPs via one home gateway device, and the device returns this
 error message for incorrectly source-addressed packets.

- notification of a correct prefix.
 if a correct prefix means /64 prefix, an ISP PE router is usually not able
 to return ICMP error message that notifies a correct prefix, as far as the
 PE and a user host is not in the same subnet.

 Notification of a correct prefix is also not feasible at the ISP routers
 located upperstream of PE. This is because they usually have only aggregated
 routes, and do not have per-user prefix information.

- security impact
 Another concern is security risk. It will be possible to inject an ICMP error
 message from remote host. This may lead to a new security attack.

Regards,

On 2010/10/22, at 3:37, Tony Hain wrote:

> http://www.ietf.org/id/draft-hain-ipv6-rpf-icmp-00.txt