Re: [v6ops] Operational Implications of IPv6 Packets with Extension Headers

Fernando Gont <> Sat, 19 September 2020 10:36 UTC

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To: Ole Troan <>
Cc: Gyan Mishra <>, IPv6 Operations <>
References: <> <>
From: Fernando Gont <>
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Date: Sat, 19 Sep 2020 07:18:38 -0300
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Subject: Re: [v6ops] Operational Implications of IPv6 Packets with Extension Headers
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Hi, Ole,

On 19/9/20 06:48, Ole Troan wrote:
>> On 19 Sep 2020, at 09:19, Fernando Gont <> wrote:
>> Hello, Gyan,
>>> On 19/9/20 01:06, Gyan Mishra wrote:
>>> Hi Fernando
>>> In this draft can we talk add point about the catch 22 situation described in RFC 7045 excerpt below bottom of introduction:
>>> I think this issue is critical to the overall issue with processing of EHs and operators filtering EHs in some cases unnecessarily.
>> What, specifically, would you like us to say about it?
>> Note: RFC6564 has not (and will not) improve the situation in this respect. Since EHs share the same namespece as "upper layer protocols", then, in order for a middlebox to know it can parse a header as in the RFC6564 format, it has to now that the corresponding "protocol number" identifies an EH (as opposed to an upper layer protocol).
>> RFC6564 would have been useful only if we had closed the door to the definition of new EHs with a new "protocol number", and had specified that any new EHs would share the same protocol number ("XX", to have been assigned by IANA at the time RFC6564 was published).
> Right, but only if the assumption that middleboxes would allow arbitrary headers in between network and transport is true.  That seems unlikely to me.

I agree. I don't think they would allow arbitrary headers in between 
network and transport. That said, *if* they were meaning to, they 
wouldn't be able to handle "unknown EHs", anyway. i.e., RFC6564 does not 
really deliver what's probably implied by the document: parsing unknown EHs.

In that sense, RFC6564 is unable to make any difference. Whether 
providing such feature (common EH format for all EHs, from now on) would 
have made a difference, is hard to tell... But I'd argue it wouldn't.

Fernando Gont
SI6 Networks
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