Re: Validation of Packet Too Big Payload using Echo Request
Fred Baker <fredbaker.ietf@gmail.com> Mon, 27 January 2020 19:40 UTC
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From: Fred Baker <fredbaker.ietf@gmail.com>
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Subject: Re: Validation of Packet Too Big Payload using Echo Request
Date: Mon, 27 Jan 2020 11:39:58 -0800
In-Reply-To: <CAOSSMjVzTmCRxLg8k+9t+j0u9iMMWa+T_8P7kVRKGLkiup_jDw@mail.gmail.com>
Cc: 6MAN <6man@ietf.org>
To: Timothy Winters <twinters@iol.unh.edu>
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PTB and PMTU activates in IPv4 applies to streams of packets, not sessions. Given that IPv6 operates from the same definitions, I don't see why it would be applied to something different in IPv6. Now, in fairness, TCP has a way to address PTB/PMTU - it changes the MSS in use for a session. UDP doesn't have anything so clear. But IMNSHO, that is a deficiency in UDP, not in ICMP. UDP, or the process using it, is informed of the limitation. It fails to act on it. > On Jan 27, 2020, at 8:45 AM, Timothy Winters <twinters@iol.unh.edu> wrote: > > Hello, > > The IPv6 Ready Logo Committee updated testing to include a test for validating the Packet Too Big message content based on the following part of 8201. > > "Nodes should appropriately validate the payload of ICMPv6 PTB > messages to ensure these are received in response to transmitted > traffic (i.e., a reported error condition that corresponds to an IPv6 > packet actually sent by the application) per [ICMPv6]." > > I've included the steps below used to verify the IPv6 implementation validates the Packet Too Big. > > Step > Action > Expected Behavior > 1. > TR1 forwards an Echo Request from TN2 to the NUT. The packet size is 1500 octets. > The NUT should respond without fragmenting the packet to the Echo Request using TR1 as a first hop. > 2. > TR1 transmits a Packet Too Big message to the NUT with an ICMPv6 Identifier does not match the Echo Reply in Step 1. > > 3. > TR1 forwards an Echo Request from TN2 to the NUT. The packet size is 1500 octets. > The NUT should respond without fragmenting the packet to the Echo Request using TR1 as a first hop. > > We received a comment that this validation shouldn't apply to ICMPv6 and it should only apply to TCP or protocols that have state. Do we think this only applies to TCP or is it valid for all traffic? > > ~Tim > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > --------------------------------------------------------------------