Re: statement regarding keepalives

Joe Touch <touch@strayalpha.com> Fri, 17 August 2018 14:40 UTC

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Subject: Re: statement regarding keepalives
From: Joe Touch <touch@strayalpha.com>
In-Reply-To: <20180816225715.GH40887@kduck.kaduk.org>
Date: Fri, 17 Aug 2018 07:40:25 -0700
Cc: Kent Watsen <kwatsen@juniper.net>, HMikael Abrahamsson <swmike@swm.pp.se>, "tsv-area@ietf.org" <tsv-area@ietf.org>, "tsvwg-ads@tools.ietf.org" <tsvwg-ads@tools.ietf.org>, "tls-ads@ietf.org" <tls-ads@ietf.org>, "netconf-chairs@ietf.org" <netconf-chairs@ietf.org>
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To: Benjamin Kaduk <kaduk@mit.edu>
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> On Aug 16, 2018, at 3:57 PM, Benjamin Kaduk <kaduk@mit.edu> wrote:
> 
> On Thu, Aug 16, 2018 at 03:52:54PM -0700, Joe Touch wrote

>> 
>> On Aug 16, 2018, at 3:10 PM, Benjamin Kaduk <kaduk@mit.edu> wrote:
>> 
>>>> Keepalives at a layer SHOULD NOT be interpreted as implying state at
>>>> any other layer.
>>> 
>>> What's going on here in the last sentence is probably a bit subtle -- a
>>> keeaplive both does not indicate "real" protocol activity but also can
>>> serve to exercise the lower protocol layers (and, even, per the previous
>>> sentence, suppresses their keepalives).
>> 
>> That may be intended but is never actually known. Lower layers can compress, cache, merge, and otherwise change the effect a transmission st one layer has on any other. 
> 
> Right, that's why it's subtle :)

It’s not subtle. There’s no way to know whether keepalives at a higher level have any desired affect at the lower level at all - except using Wireshark to trace the packets sent.

That’s why users SHOULD NOT try to affect lower level keepalives using higher level ones.  (it’s not MUST NOT because there’s no strict harm, except that it simply can’t be known whether it achieved its desired effect).

Joe