Re: [EXT] Re: Last Call: <draft-ietf-6man-rfc2460bis-08.txt> (Internet Protocol, Version 6 (IPv6) Specification) to Internet Standard

Brian E Carpenter <> Tue, 14 February 2017 23:34 UTC

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Subject: Re: [EXT] Re: Last Call: <draft-ietf-6man-rfc2460bis-08.txt> (Internet Protocol, Version 6 (IPv6) Specification) to Internet Standard
To: David Mozes <>, Tal Mizrahi <>, Mark Smith <>
References: <> <> <> <>
From: Brian E Carpenter <>
Organization: University of Auckland
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Date: Wed, 15 Feb 2017 12:34:52 +1300
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David, Tal,

Note that if a HbH option is tagged "1 - Option Data may change en-route"
it is excluded from AH anyway. But if you insert an option, or extend
its length while modifying it, you will break all forms of PMTUD.


On 15/02/2017 03:27, David Mozes wrote:
> Hi * ,
> I am also supporting the insertion of in-band telemetry like INT along with the  actual data packet .
> It is for sure a valid use case for the modern networking including data center. 
> There are several proposals how to embedded telemetry information   some of them are with in nvo3 tannling protocols 
> (Vxlan-GPE,Geneve) Spring and other  . 
> I think that ipv6 hbh is the "cleanest"  way to add such info.
> 	1) I don't see any and advantages on the other  proposals (NVO3 ,SPRING) over IPV6 hbh.
> 	2))As far as security In the IPsec community, AH is pretty much considered deprecated, a failed experiment.They  are  prefer to use   ESP for authentication as well.
> The postal system and the letter is very nice e example  . I will treat the adding ipv6-hbh info as stamps on the envelops ,since we are not touching  the data gram itself just the envelope
> Thx
> David
> -----Original Message-----
> From: ipv6 [] On Behalf Of Tal Mizrahi
> Sent: Tuesday, February 14, 2017 3:37 PM
> To: Mark Smith <>
> Cc:;; IETF Discussion list <>;
> Subject: RE: [EXT] Re: Last Call: <draft-ietf-6man-rfc2460bis-08.txt> (Internet Protocol, Version 6 (IPv6) Specification) to Internet Standard
> Hi Mark,
> I certainly agree that hop-by-hop insertion/modification introduces potential security vulnerabilities.
> Therefore, as I pointed out below, I would recommend to tackle this by defining something along the lines of “Hop-by-hop extensions can be inserted/removed/modified/processed by intermediate nodes *if* [……..] and the possible consequences are [……..]”
> For example, hop-by-hop handling can be restricted only to a single administrative domain, or only to tunnels (as in the zero checksum case). 
> Regards,
> Tal.
>> -----Original Message-----
>> From: Mark Smith []
>> Sent: Monday, February 13, 2017 6:07 PM
>> To: Tal Mizrahi
>> Cc:; IETF Discussion list; draft-ietf-6man- 
>> Subject: [EXT] Re: Last Call: <draft-ietf-6man-rfc2460bis-08.txt> 
>> (Internet Protocol, Version 6 (IPv6) Specification) to Internet 
>> Standard
>> External Email
>> ----------------------------------------------------------------------
>> Hi,
>> On 14 February 2017 at 00:43, Tal Mizrahi <> wrote:
>>> Hi,
>>> Good discussion regarding the text about the hop-by-hop extension.
>>> In my opinion there is a valid use case for intermediate nodes that 
>>> insert/remove/modify/process hop-by-hop extensions. Examples: IOAM, INT.
>>> Since there is a use case, I believe we need explicit text about 
>>> intermediate handling of hop-by-hop extensions.
>> Imagine you sent a letter through the postal system, and the postal 
>> system wanted to add information to that letter, that is then to be 
>> removed before the letter arrives at its final destination.
>> The postal system have at least two choices as to how to add that information.
>> They could:
>> (a) unstick your envelope's seal, insert the information, reseal the 
>> envelope so well you can't tell and send it on its way, some how 
>> flagging to a destination device within the postal system that this 
>> specific envelop needs to be openned, a specific page removed, and then resealed.
>> (b) take a new envelope with new internal postal system source and 
>> destination address information, insert your letter without touching it 
>> in addition to the new information, and then sending it on its way.
>> Imagine that the information to be added by the postal system is 
>> printed on the same type of paper and is written in the same font as 
>> you've chosen to use to write your letter.
>> Have a think about these two methods, what could fail with each of 
>> them, and what the consequences may be if any of those failures occur.
>> Have a think of the benefits of each method, and whether they're worth 
>> it compared to the failure mode costs and consequences for the method.
>>> This [somewhat] reminds me of the discussion a few years ago about 
>>> the IPv6/UDP zero checksum. The WG ended up defining that “Zero 
>>> checksum is permitted in IPv6/UDP *if* [……..] and the possible consequences are [……..]”.
>> That is a far more trivial change to the packet - it is allowing a 
>> value in an existing field that was formerly prohibited, and nodes that 
>> did not understand that value would drop the packet because that is 
>> what they had been specified to do if they received this prohibited value. In other words, existing implementations '
>> behaviour when this formerly unexpected value was encountered had 
>> already been specified and deployed.
>>> I would argue that regarding hop-by-hop extension handling we also 
>>> need to define that “Hop-by-hop extensions can be 
>>> inserted/removed/modified/processed by intermediate nodes *if* [……..] 
>>> and the possible consequences are [……..]”.
>> Some things that are possible to do in theory shouldn't be done in 
>> practice, because the consequences when their implementations fail can 
>> be severe and outweigh the benefits.
>> In theory, inserted EHs will be removed 100% of the time. In practice 
>> they won't be, because implementations can have bugs and they can also 
>> fail in unexpected ways e.g., hardware faults.
>> Regards,
>> Mark.
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