Re: [Starlink] some details on the DTN, bundle protocol, and a capacity question

[Dave Taht <dave.taht@gmail.com>]

On Sat, Dec 11, 2021 at 7:15 PM Vint Cerf <vint@google.com> wrote:
>
> I haven't pushed to much further until we get some real data from running implementations. I also hope we can develop a simulator from which we might derive measurements to compare with actual data and modeled (queueing theoretic) data.

I am just going to ignore the way this thread went for now. What I was
mostly asking was what version of dtn was the most promising for an
embedded (e.g. cerowrt  II) implementation?

https://dtn7.github.io/ looks very promising, especially the rust
bits. Rust lets me sleep better and we are moving some support for it
into openwrt's next release.

 https://github.com/morgenroth/ibrdtn  is undermaintained but was
already ported to openwrt, and is lighter weight. There's another one
targetted at microcontrollers (  https://upcn.eu/ ), but not the FRAM
one we used on a previous space-related project... really liked those
FRAMs....

As for the simulator side, what/where are the requirements? I confess
to wanting to feed forward the asterank, or celestia, or nasa's new
https://eyes.nasa.gov/apps/asteroids/#/asteroids into it another 10
years and plunk 28k nodes into it....





> v
>
>
> On Sat, Dec 11, 2021 at 9:58 PM Dave Taht <dave.taht@gmail.com> wrote:
>>
>> A good deep dive into DTN with vint cerf is here:
>> https://www.datacenterdynamics.com/en/analysis/vint-cerfs-interplanetary-ambitions/
>>
>>  I went looking for existing source code for it, some here:
>> https://projet.liris.cnrs.fr/riot/dtn_implementations_survey.html
>>
>> From the interview...
>>
>> Q: "So for store and forward to work, what is the level of storage
>> each node needs to the speed of the network?"
>>
>> VC: That's such a good question. So guess what, I have the same
>> question. And I said, 'Okay, where do I go to get an answer to that?'
>> And that is the capacity question: What capacity of this DTN network,
>> given if I know where the nodes are, and I know what the physics are.
>> And I know what the data rates could be. I have a traffic matrix. Do I
>> have a network which is capable of supporting the demand?
>>
>> That's the formulation of the question you're asking. So I went to the
>> best possible source for this question, Leonard Kleinrock at UCLA. He
>> is the father of the use of queueing theory to analyze store and
>> forward networks way back in 1961/62, doing his dissertation at MIT on
>> this topic, not in aid of the interplanetary network, but more general
>> question on store and forward networking.
>>
>> And so he did some fantastic work, he broke the back of the problem
>> with what was called the independence principle. But he left MIT and
>> came to UCLA in the '60s, he was on my thesis committee. And he's
>> still very, very active. He's 87, still blasting on.
>>
>> So I sent him a note saying, look, here's the problem. I've got this
>> collection of notes, and I've got a traffic matrix, and I have this
>> DTN environment, how do I calculate the capacity of the system so I
>> know, I'm not gonna overwhelm it.
>>
>> And, you know, I figured it would take him a while and maybe find a
>> graduate student. So *two days later*, I get back two pages of dense
>> math saying, okay, here's how you formulate this problem. Now, I
>> didn't get all of the answer. I still don't have all of the answer.
>> But I know I have one of the best minds in the business looking at the
>> problem."
>>
>> That was back in august of this year, made any progress?
>>
>> --
>> I tried to build a better future, a few times:
>> https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org
>>
>> Dave Täht CEO, TekLibre, LLC
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>
>
>
> --
> Please send any postal/overnight deliveries to:
> Vint Cerf
> 1435 Woodhurst Blvd
> McLean, VA 22102
> 703-448-0965
>
> until further notice
>
>
>


-- 
I tried to build a better future, a few times:
https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org

Dave Täht CEO, TekLibre, LLC