Re: I-D Action: draft-ietf-6man-icmp-limits-05.txt

[Bob Hinden <[e-mail]>]

Tom,

I took a look at the new draft.  Thanks for fixing most of the issues I raised.  Much better.

I think there is still an issue with Section 3 that defines a new code point for the Destination unreachable message.

RFC4884 Section 4.4 "ICMPv6 Destination Unreachable” in the header format includes:

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    As much of invoking packet                 |
     +                as possible without the ICMPv6 packet          +
     |                exceeding the minimum IPv6 MTU [RFC4443]       |

but in draft-ietf-6man-icmp-limits-05 shows:

  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ M
  |                       Original Datagram                       | P
  ~     Internet Header + leading octets of original datagram     ~ |
  |                                                               | |

This is a change from RFC4884.  Further, the draft has:

     Original Datagram
        As much of invoking packet as possible without exceeding the
        minimum ICMPv6 packet minus twelve bytes (for the ICMP
        extension structure and the ICMP extension object) and any
        necessary padding. The Original Datagram field MUST be zero
        padded to the nearest 64-bit boundary [RFC4884]. If the
        original datagram did not contain 128 octets, the Original
        Datagram field MUST be zero padded to 128 octets.

I can’t find anything in RFC4884 that says to reduce the size of the original datagram to allow the extensions to fit.   This is a change from what RFC4884 specifies.    RFC4884 specifically says:

   The syntax and semantics of all fields are unchanged from RFC 4443.
   However, a length attribute is added to the second word.  The length
   attribute represents length of the padded "original datagram" field,
   measured in 64-bit words.

I think this change to RFC4884 is out of scope for a document that wants to define a new code point.

I think a possible solution (beside not changing the RFC4884 format) is to say the new extensions can only be sent with packets that don’t exceed the minimum IPv6 MTU.   Or else, add a code point to the Parameter Problem as Ron suggested, even though it’s not idea for the reasons you pointed out.

Bob



> On Sep 10, 2019, at 10:47 AM, Tom Herbert <[e-mail]> wrote:
> 
> Hello,
> 
> I've submitted this draft to address the comments in the chairs' review.
> 
> Thanks,
> Tom
> 
> On Tue, Sep 10, 2019 at 10:40 AM <[e-mail]> wrote:
>> 
>> 
>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>> This draft is a work item of the IPv6 Maintenance WG of the IETF.
>> 
>>        Title           : ICMPv6 errors for discarding packets due to processing limits
>>        Author          : Tom Herbert
>>        Filename        : draft-ietf-6man-icmp-limits-05.txt
>>        Pages           : 15
>>        Date            : 2019-09-10
>> 
>> Abstract:
>>   Network nodes may discard packets if they are unable to process
>>   protocol headers of packets due to processing constraints or limits.
>>   When such packets are dropped, the sender receives no indication so
>>   it cannot take action to address the cause of discarded packets. This
>>   specification defines several new ICMPv6 errors that can be sent by a
>>   node that discards packets because it is unable to process the
>>   protocol headers. A node that receives such an ICMPv6 error may be
>>   able to modify what it sends in future packets to avoid subsequent
>>   packet discards.
>> 
>> 
>> The IETF datatracker status page for this draft is:
>> https://datatracker.ietf.org/doc/draft-ietf-6man-icmp-limits/
>> 
>> There are also htmlized versions available at:
>> https://tools.ietf.org/html/draft-ietf-6man-icmp-limits-05
>> https://datatracker.ietf.org/doc/html/draft-ietf-6man-icmp-limits-05
>> 
>> A diff from the previous version is available at:
>> https://www.ietf.org/rfcdiff?url2=draft-ietf-6man-icmp-limits-05
>> 
>> 
>> Please note that it may take a couple of minutes from the time of submission
>> until the htmlized version and diff are available at tools.ietf.org.
>> 
>> Internet-Drafts are also available by anonymous FTP at:
>> ftp://ftp.ietf.org/internet-drafts/
>> 
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