Re: [icnrg] Spencer Dawkins' Yes on draft-oran-icnrg-qosarch-05: (with COMMENT)

"David R. Oran" <daveoran@orandom.net> Thu, 17 September 2020 13:45 UTC

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From: "David R. Oran" <daveoran@orandom.net>
To: "Spencer Dawkins at IETF" <spencerdawkins.ietf@gmail.com>
Cc: "Dirk Kutscher" <ietf@dkutscher.net>, icnrg-chairs@ietf.org, ICNRG <icnrg@irtf.org>, draft-oran-icnrg-qosarch@ietf.org, "The IRSG" <irsg@irtf.org>
Date: Thu, 17 Sep 2020 09:45:35 -0400
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Subject: Re: [icnrg] Spencer Dawkins' Yes on draft-oran-icnrg-qosarch-05: (with COMMENT)
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Thanks Spencer - adding “only” in that sentence helps a lot. I’ll 
note it for the next revision before sending to RFCed.

On 17 Sep 2020, at 9:40, Spencer Dawkins at IETF wrote:

> Hi, Dirk,
>
> I'm fine with most of these replies. On one of my comments, I wasn't 
> clear
> enough (please see below).
>
> Best,
>
> Spencer
>
> On Thu, Sep 17, 2020 at 3:44 AM Dirk Kutscher <ietf@dkutscher.net> 
> wrote:
>
>> Thanks a lot for looking into this, Spencer!
>>
>> I'm not an ICN guy, but I can translate all of the terms on both 
>> sides of
>> Table
>> 1, except for "flow balance". The term isn't mentioned anywhere else,
>> except
>> with a reference to I-D.oran-icnrg-flowbalance, which has a very 
>> clear
>> definition in its abstract.
>>
>> This captures the idea that there is a one-to-one
>> correspondence between requests for data, carried in Interest
>> messages, and the responses with the requested data object, carried
>> in Data messages.
>>
>> Would it make sense to include some or all of that definition earlier 
>> in
>> the
>> document, or just including a pointer to the discussion draft near 
>> where
>> the
>> term first appears? The current pointer to the discussion draft 
>> happens 14
>> pages into this draft, which doesn't seem helpful if a reader doesn't
>> understand the term used on page 3.
>>
>> Fair comment. It's a well-understood term for ICN folks, but we could
>> consider addressing a broader audience here. There is also
>> https://datatracker.ietf.org/doc/rfc8793/ (Terminology) that mentions
>> flow balance in the big-picture-overview -- that could be referenced 
>> as
>> well if a revision was to be done.
>>
>> This text
>>
>> Further, accumulated experience seems to indicate that QoS is helpful
>> in a fairly narrow range of network conditions:
>>
>> seems backwards to me, because the list of bullets that follows 
>> describe
>> where
>> QoS is NOT helpful:
>>
>> IMO, this is just trying level expectations and debunk some QoS myths 
>> that
>> might aggravate the understanding of the document.
>>
>> The draft has additional text with examples after this one:
>>
>> Nevertheless, though not universally deployed, QoS is advantageous at
>> least for some applications and some network environments.
>>
>> * applications with steep utility functions [Shenker2006], such as
>>   real-time multimedia
>>
>>
>>    -
>>
>>    applications with safety-critical operational constraints, such as
>>    avionics or industrial automation
>>    -
>>
>>    dedicated or tightly managed networks whose economics depend on
>>    strict adherence to challenging service level agreements (SLAs)
>>
>> I was thinking that this illustrates it quite nicely. Do you think 
>> that
>> more is needed?
>>
> I agree that the examples are good. What I SHOULD have said in my 
> comment
> was that the leading sentence says "QoS is helpful in a fairly
> narrow range" but the examples are for cases where it is not helpful 
> :-)
>
> I should have suggested "QoS is only helpful in a fairly narrow range" 
> -
> adding "only". Then the examples make sense - "not helpful in this 
> case, or
> this one, or this one".
>
> Best,
>
> Spencer
>
>> I think this text
>>
>> This may
>> allow less pessimistic rate adjustment schemes than the Additive
>> Increase, Multiplicative Decrease (AIMD) with .5 multiplier that
>> is used on TCP/IP networks.
>>
>> is approximately correct today, but TSVWG is certainly trying to 
>> change
>> that
>> with ECT(1) experimentation as per 
>> https://tools.ietf.org/html/rfc8311.
>> Perhaps
>> "that is commonly used on TCP/IP networks"?
>>
>> Probably nice to have in case a revision is done.
>>
>> I'm a bit uncomfortable with "likely to incur a mobility event within 
>> an
>> RTT
>> (or a few RTTs)", because really short-horizon distributed decisions 
>> seem
>> to be
>> problematic in a lot of path aware networking proposals.
>>
>> * A QoS treatment indicating a mobile consumer likely to incur a
>> mobility event within an RTT (or a few RTTs). Such a treatment
>> would allow a mobile network operator to preferentially cache the
>> data at a forwarder positioned at a _join point_ or _rendezvous
>> point_ of their topology.
>>
>> How badly do you need the text following "likely to incur a mobility
>> event"? It
>> seems like deleting it would be just as clear and accurate.
>>
>> So, here I agree that, in a non-ICN context, the original text could 
>> raise
>> some eye brows. However in this context, I don't see a need for 
>> change,
>> because of the different nature of ICNs (conceptually less need for
>> path-awareness) and light-weight mobility management approaches that 
>> ICNs
>> enables.
>>
>> Thanks,
>> Dirk
>>

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DaveO