Re: [manet] New DLEP extension draft for WG

Rick Taylor <rick@tropicalstormsoftware.com> Wed, 27 January 2021 15:51 UTC

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From: Rick Taylor <rick@tropicalstormsoftware.com>
To: "manet@ietf.org" <manet@ietf.org>, "henning.rogge@fkie.fraunhofer.de" <henning.rogge@fkie.fraunhofer.de>
Thread-Topic: [manet] New DLEP extension draft for WG
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Date: Wed, 27 Jan 2021 15:49:22 +0000
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Subject: Re: [manet] New DLEP extension draft for WG
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Hi Henning,

> 
> I finally got to the point where I had time to publish the first
> parts of my DLEP extensions I would like the Manet WG to adopt. I
> talked with Ronald and we agreed that I keep the drafts quite
> "narrow".

"Narrow" is good, but in my opinion if you have <6 data items that are
all very much in the same context, e.g. Radio Signal Info, it mike make
sense to roll them all up into 1 extension.  I suppose the test would
be that if an implementation supports 1 data item, then it probably
could support the others, but that is a little subjective.

The disadvantage is that you then need to specify which data items MUST
be used by an implementation supporting the extension, and which are
optional.

> 
> https://datatracker.ietf.org/doc/draft-rogge-manet-dlep-radio-band/​
> 
> At the moment I plan to do two more drafts about PHY aspects of the
> radio (signal strength related stuff and channel utilization) before
> moving to MAC related TLV extensions.

I think these radio data items sound like they are logically all part
of the same extension.


I do have a question: As DLEP is primarily about informing layer-3
devices about dynamic layer-2 capabilities, are radio signal metrics
really of use to a router?  To me they sound a lot like layer-1
information, if you get my meaning, and I wonder why a router would
even care?

Can you explain why you think these data items are important to a
layer-3 device?  I think I'm looking for a "rationale" section in the
draft.

I understand that you have done some work before around Airtime Cost
Metrics derived from signal information, so I wonder whether the modem
should be exposing a derived data item (post-processing) rather than
the raw radio signal data items (pre-processing).  My assumption is
that the DLEP protocol is significantly slower than the computation. 

I suppose the counter-argument is that there is really no such thing as
a "useless" metric, and I can imagine some routers in the near future
using AI to predict link behaviour - I expect someone is already doing
a PhD on that right now!

Cheers,

Rick