Re: [v6ops] I-D Action: draft-ietf-v6ops-ipv6-ehs-packet-drops-01.txt

Fernando Gont <fgont@si6networks.com> Wed, 14 October 2020 21:54 UTC

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To: Brian E Carpenter <brian.e.carpenter@gmail.com>, "Dale W. Carder" <dwcarder@es.net>, Fernando Gont <fernando@gont.com.ar>
Cc: v6ops@ietf.org, draft-ietf-v6ops-ipv6-ehs-packet-drops.authors@ietf.org
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From: Fernando Gont <fgont@si6networks.com>
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Date: Wed, 14 Oct 2020 18:28:59 -0300
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Subject: Re: [v6ops] I-D Action: draft-ietf-v6ops-ipv6-ehs-packet-drops-01.txt
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Hi, Brian,

On 14/10/20 17:06, Brian E Carpenter wrote:
> On 15-Oct-20 05:39, Fernando Gont wrote:
> ...
>>> I am not sure if I agree with the last paragraph of 6.1 which opines on
>>> the low adoption of rfc6437-style flow label hash entropy.
>>
>> We don't argue low-entropy, but issues with the Flow  Label
>> implementation. See e.g.:
>> https://blog.apnic.net/2018/01/11/ipv6-flow-label-misuse-hashing/
>>
>>
>>
>>> I would
>>> expect that the current low adoption in ecmp implementations is a
>>> chicken/egg problem.  If you have a product that needs to hash and you are
>>> not confident there is enough adoption in host stacks, you are still forced
>>> to hunt for entropy from the upper-protocol protocols.  Otherwise all the
>>> legacy host traffic with the flow label set to 0 risks getting hashed
>>> entirely to one side or face reordering.
>>
>> We're just stating that there's marginal usage of the Flow Label, which
>> is what the work by Cunha et al seems to indicate. As to the possible
>> consequences, part might be LBs lagging behind host implementations. But
>> issues in the Flow Label implementation might have also discouraged its use.
>>
>> That said, the important info that Section 6.1 is meant to convey is
>> that there still seems to be marginal use of the FL. And also note that
>> issues have been found in FL implementations. -- i.e., we're not trying
>> to infer why there's marginal use of the FL.
>>
>> If you think this warrants some tweaks in the text, please do let us know.
> 
> I just re-read that section and sadly I think it is still correct.

Thanks a lot for double-checking!

Regards,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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