Subject: [Technical Errata Reported] RFC6936 (4341)

From: RFC Errata System <[email-masked]>
Date: Mon, 20 Apr 2015 21:35:27 -0700 (PDT)

The following errata report has been submitted for RFC6936,
"Applicability Statement for the Use of IPv6 UDP Datagrams with Zero Checksums".

--------------------------------------
You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=6936&eid=4341

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Type: Technical
Reported by: Brian Carpenter <[email-masked]>

Section: 1.3.5

Original Text
-------------
The ingress of a tunnel seeking to provide good
entropy in the flow label field would therefore need to create a
random flow label value and keep corresponding state so that all
packets that were associated with a flow would be consistently given
the same flow label.  Although possible, this complexity may not be
desirable in a tunnel ingress.

Corrected Text
--------------
The ingress of a tunnel seeking to provide good
entropy in the flow label field would therefore need to create a
pseudo-random flow label value using a stateless method
as described in [RFC6438] so that all
packets that were associated with a flow would be consistently given
the same flow label.

Notes
-----
It is incorrect that a stateful method is needed, and presumably that
was the complexity judged undesirable. Also, we shouldn't say "random"
when we mean "pseudo-random."

Instructions:
-------------
This erratum is currently posted as "Reported". If necessary, please
use "Reply All" to discuss whether it should be verified or
rejected. When a decision is reached, the verifying party (IESG)
can log in to change the status and edit the report, if necessary. 

--------------------------------------
RFC6936 (draft-ietf-6man-udpzero-12)
--------------------------------------
Title               : Applicability Statement for the Use of IPv6 UDP Datagrams with Zero Checksums
Publication Date    : April 2013
Author(s)           : G. Fairhurst, M. Westerlund
Category            : PROPOSED STANDARD
Source              : IPv6 Maintenance
Area                : Internet
Stream              : IETF
Verifying Party     : IESG

---

From: joel jaeggli <[email-masked]>
Date: Mon, 20 Apr 2015 21:46:30 -0700

anyone care to comment?

joel

On 4/20/15 9:35 PM, RFC Errata System wrote:
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---

From: Ole Troan <[email-masked]>
Date: Tue, 21 Apr 2015 09:20:56 +0200

> anyone care to comment?

I believe the corrected text in the errata is correct.

http://www.ietf.org/iesg/statement/errata-processing.html
	• Only errors that could cause implementation or deployment problems or significant confusion should be Verified.

if the current text led implementors to dismiss setting the flow label because of the wrong assumption that per flow state was needed at tunnel ingress, then I think that’s confusing and would also make flow label ECMP deployments problematic.

following that logic the errata should be verified.

cheers,
Ole

---

From: Mark ZZZ Smith <[email-masked]>
Date: Tue, 21 Apr 2015 07:47:04 +0000 (UTC)

I agree with Brian's update, I think stateless LB is better.
(Strangely and coincidently, my OpenWRT router reported I received one today:
[  422.320000] IPv6: udp checksum is 0

)

Regards,Mark.
      From: joel jaeggli <[email-masked]>
 To: RFC Errata System <[email-masked]>; [email-masked]; [email-masked]; [email-masked]; [email-masked]; [email-masked]; [email-masked] 
Cc: [email-masked] 
 Sent: Tuesday, 21 April 2015, 14:46
 Subject: Re: [Technical Errata Reported] RFC6936 (4341)
   
anyone care to comment?

joel

---

From: [email-masked]
Date: Tue, 21 Apr 2015 09:09:58 +0100

I agree with this update. I think it is a useful correction.

Gorry

>  To: RFC Errata System <[email-masked]>; [email-masked];
> [email-masked]; [email-masked];
> [email-masked]; [email-masked]; [email-masked]
> Cc: [email-masked]

---

From: Magnus Westerlund <[email-masked]>
Date: Tue, 21 Apr 2015 10:45:12 +0200

I also support approving this Errata.

Cheers

Magnus

[email-masked] skrev den 2015-04-21 10:09:
>> [ Â 422.320000] IPv6: udp checksum is 0
>>
>> )
>>
>>
>> Regards,Mark.
>>> the same flow label.Â  Although possible, this complexity may not be
>>> TitleÂ  Â  Â  Â  Â  Â  Â  : Applicability Statement for the Use of IPv6
>>> UDP Datagrams with Zero Checksums
>>> Publication DateÂ  Â  : April 2013
>>> Author(s)Â  Â  Â  Â  Â  : G. Fairhurst, M. Westerlund
>>> CategoryÂ  Â  Â  Â  Â  Â  : PROPOSED STANDARD
>>> SourceÂ  Â  Â  Â  Â  Â  Â  : IPv6 Maintenance
>>> AreaÂ  Â  Â  Â  Â  Â  Â  Â  : Internet
>>> StreamÂ  Â  Â  Â  Â  Â  Â  : IETF
>>> Verifying PartyÂ  Â  : IESG
>>>

-- 

Magnus Westerlund

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Färögatan 6                 | Mobile +46 73 0949079
SE-164 80 Stockholm, Sweden | mailto: [email-masked]
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---

From: Brian Haberman <[email-masked]>
Date: Tue, 21 Apr 2015 08:07:37 -0400

Hi all,
     While I agree with the sentiment that the proposed updated text is
more appropriate, we are on a slippery slope as to this being errata.
This is a technical change and not fixing an error.  Can someone point
to a discussion where a reference to 6438 and stateless methods occurred
and there was consensus to put that in 1.3.5?

     If not, this seems more like a new draft to obsolete 6936.

Regards,
Brian

---

From: [email-masked]
Date: Tue, 21 Apr 2015 16:06:46 +0100

I'll read the surrounding para's carefully and get back.

Gorry

---

From: Brian E Carpenter <[email-masked]>
Date: Wed, 22 Apr 2015 12:17:11 +1200

>      If not, this seems more like a new draft to obsolete 6936.

Good point. How about "hold for document update" to resolve the
open errata report?

Mea culpa, because I didn't ever review that part of
draft-ietf-6man-udpzero.

    Brian C

---

From: Ole Troan <[email-masked]>
Date: Wed, 22 Apr 2015 09:38:45 +0200

Brian,

>     If not, this seems more like a new draft to obsolete 6936.

I do see your point of view. technical errata are always going to be a judgement call.
I think we also need to consider the alternatives. the cost and energy required to re-issue a new document is quite high. the risk of not accepting this as an errata, is that the issue will be dropped and forgotten.

looking at:

the important point here is if this issue creates "deployment problems or significant confusion”.

I think it might do that.

with regards to the issue if this changes consensus or not. the IETF published RFC6438 prior to this document, with consensus that there are stateless methods calculating the flow label. it is an error in 6936 requiring a stateful method. I see no indication anywhere that the intention of 6936 was to change the 6438 consensus.

cheers,
Ole

---

From: [email-masked]
Date: Wed, 22 Apr 2015 08:44:58 +0100

I wish to change my opinion also (SORRY): I prefer to hold.

To be clear:

* "random" was indeed intended to mean "pseudorandom".

* RFC6936 references ECMP [RFC6438 ] flow marking - seeking to say this
was desirable, but not always practical at present. This was written in
parallel with RFC6438.

* RFC6936 only used a stateful ECMP example. It would have been better to
also mention stateless mapping, there is no reason why this was not
included.

However - I do not think the Errata would change the meaning, and the
clarification is not "clear". Simply changing a couple of words confuses
the meaning of the surrounding paragraphs

Gorry

>>>>> (Strangely and coincidently, my OpenWRT router reported I received
>>>>> one
>>>>> today:

---

From: [email-masked]
Date: Wed, 22 Apr 2015 08:45:07 +0100

To be clear:

Gorry

---

From: Brian Haberman <[email-masked]>
Date: Wed, 22 Apr 2015 08:09:21 -0400

Hi Ole,

On 4/22/15 3:38 AM, Ole Troan wrote:
>> more appropriate, we are on a slippery slope as to this being
>> errata. This is a technical change and not fixing an error.  Can
>> someone point to a discussion where a reference to 6438 and
>> stateless methods occurred and there was consensus to put that in
>> 1.3.5?
>> 
> I do see your point of view. technical errata are always going to be
> a judgement call. I think we also need to consider the alternatives.
> the cost and energy required to re-issue a new document is quite
> high. the risk of not accepting this as an errata, is that the issue
> will be dropped and forgotten.
> 
> looking at: 

I am not sure I agree.  The text in 1.3.5 is nebulous, but it does not
require a stateful method.  It says that corresponding state is kept.
If there is no corresponding state, an implementation is still
conforming to 1.3.5.

> 
> with regards to the issue if this changes consensus or not. the IETF
> published RFC6438 prior to this document, with consensus that there
> are stateless methods calculating the flow label. it is an error in
> 6936 requiring a stateful method. I see no indication anywhere that
> the intention of 6936 was to change the 6438 consensus.

Can you point to the text that requires a stateful method?  I tend to
agree with Brian & Gorry that the text is not crisp, but that HFDU is
appropriate.  I would rather see a new RFC that cleans this up so that
consensus is clear.

Regards,
Brian

---

From: Ole Troan <[email-masked]>
Date: Wed, 22 Apr 2015 14:30:04 +0200

Brian,

> If there is no corresponding state, an implementation is still

I read “corresponding state” implying stateful, but oh well.

> appropriate.  I would rather see a new RFC that cleans this up so that

my take is that it isn’t worth the cost to re-issue a new RFC. I will not stop anyone having the energy though.
as long as it isn’t reject I can live with HFDU.

cheers,
Ole

cheers,
Ole