Subject: a problem of IPv6 over PPP(draft-ietf-ipv6-over-ppp-v2-02.txt)

From: "Su Thunder" <[email-masked]>
Date: Thu, 21 Sep 2006 14:16:30 +0000

For example,the IP address of one end(Router A) of the PPP link is 
1000::1/64,the one of the other end(Router B) is 1000::2/64.Suppose packet 
with a destination IP address of 1000::3/64 is sent from Router A to Router 
B.On Router B,the packet's destination IP address matches 1000::/64,then 
the packet is sent back to Router A through the interface from which it was 
received,at the mean time,an ICMP Redirect message is sent to Router A.Then 
on Router A,for the same reason,the packet is sent back to Router B with an 
ICMP Redirect message being sent to Router B.The process continues until 
the packet's Hop Limit value is decremented to zero.
The way to solve the problem.
If the destination IP address of a packet matches an on-link prefix of a 
PPP link,and the destination IP address is not the IP address of the other 
end of the PPP link,then the packet must be discarded by the PPP 
link-layer.
Or the problem is already specified in draft-ietf-ipv6-over-ppp-v2-02.txt 
or any other RFC,and I ignore it?

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From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Sat, 23 Sep 2006 16:15:14 +0900

>>>>> On Thu, 21 Sep 2006 14:16:30 +0000, 
>>>>> "Su Thunder" <[email-masked]> said:

> or any other RFC,and I ignore it?

See the following part of RFC4443:

   One specific case in which a Destination Unreachable message is sent
   with a code 3 is in response to a packet received by a router from a
   point-to-point link, destined to an address within a subnet assigned
   to that same link (other than one of the receiving router's own
   addresses).  In such a case, the packet MUST NOT be forwarded back
   onto the arrival link.
(Section 3.1)

It should also be noted that the redirect message in your example
would not be sent (regardless of the existence of RFC4443) unless the
packet was originated at Router A.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]