Date: Fri, 25 Jan 2008 14:51:10 -0700
From: Yinghui Yao <Yinghui.Yao@alcatel-lucent.com>
Subject: [users:00488] RFC 1981 undersized PMTU test
To: users@tahi.org
Message-Id: <479A59CE.6010007@alcatel-lucent.com>
In-Reply-To: <479A5770.6050101@alcatel-lucent.com>
References: <47746300.1020404@cn.fujitsu.com> <477851F3.9030402@cn.fujitsu.com> <20080101222240.r1dqh8wlc000gk4g@webmail.corp.redhat.com> <BDC75A1E-9BF3-4B92-9C17-0170BAB06005@tahi.org> <4797CE07.7050202@alcatel-lucent.com> <479A06AE.90004@alcatel-lucent.com> <20080125163725.GB14346@pingi.kke.suse.de> <479A35AE.9030602@redhat.com> <479A5770.6050101@alcatel-lucent.com>
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Self_Test_1.4.9 PMTU test #9 seems to test RFC 1981 section 4 statement

"A node MUST NOT reduce its estimate of the Path MTU below the IPv6
   minimum link MTU.

      Note: A node may receive a Packet Too Big message reporting a
      next-hop MTU that is less than the IPv6 minimum link MTU.  In that
      case, the node is not required to reduce the size of subsequent
      packets sent on the path to less than the IPv6 minimun link MTU,
      but rather must include a Fragment header in those packets [IPv6-
      SPEC]. "

Could anyone please shed some light on why the RFC requires this. Why should
a node pay attention to an malformed ICMP packet, let alone adding a frag
header to a unfrag packet? Why? Appreciate it.

Thanks,
Yinghui Yao
Alcatel-Lucent