Subject: I-D ACTION:draft-ietf-ipngwg-p2p-pingpong-00.txt

From: [email-masked]
Date: Tue, 17 Jul 2001 10:20:22 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the IPNG Working Group of the IETF.

	Title		: Avoiding ping-pong packets on point-to-point links
	Author(s)	: J. Hagino et al.
	Filename	: draft-ietf-ipngwg-p2p-pingpong-00.txt
	Pages		: 5
	Date		: 16-Jul-01
	
In IPv6 point-to-point link operation, there is a significant
possibility of aberrant behavior in that packets may ping-pong between
the two ends of the link.  The problem can lead to wasted bandwidth and
can possibly be abused by malicious parties.  This document provides an
analysis and solution to the problem.

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From: Pekka Savola <[email-masked]>
Date: Tue, 17 Jul 2001 18:41:40 +0300 (EEST)

> 	Title		: Avoiding ping-pong packets on point-to-point links

Assuming the scenario in the above:

     Router B
       |P::b
       |
       | Point-to-point link, P::/64
       |
       |P::a
     Router A

If some nastie sent a packet with source= P::c, destination P::d, you
might end up in an endless ping-pong loop of ICMP error messages, or...?
(does the "no icmp error sent due to received icmp error" prevent this?)

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Wed, 18 Jul 2001 10:19:08 +0900

>>>>> On Tue, 17 Jul 2001 18:41:40 +0300 (EEST), 
>>>>> Pekka Savola <[email-masked]> said:

> (does the "no icmp error sent due to received icmp error" prevent this?)

Yes, it is.  Additionally, even if we did not have the rule, we would
not see such infinite iteration of icmp6 errors, because the source
address of the error packet from Router B would P::b, which is
a perfectly legal address.  We would only see one more error.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]
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From: [email-masked]
Date: Wed, 18 Jul 2001 16:34:45 +0900

>a perfectly legal address.  We would only see one more error.

	to illustrate the situation better, it should be like this.
	(correct me if I'm wrong)

itojun

without the behavior change on the draft:

router A -> router B	src=P::c, dst=P::d, TTL=x (original packet)
router B -> router A	src=P::c, dst=P::d, TTL=x - 1 (original packet)
.... (forward until TTL reaches 0)

with the behavior change on the draft:

router A -> router B	src=P::c, dst=P::d (original packet)
	(router B detects the anomaly on forwarding, and suppress
	the packet forwarding and raise address unreachable)
router B -> router A	src=P::b, dst=P::c, icmp6 address unreachable
	(there'll be no response, end)
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