Dmytro Piatkivskyi [ARCHIVE] / is on Nostr

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🗓️ Active from 2018-07-01 to 2018-07-24
💬 Posted a total of 4 messages
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2023-06-09 12:51:14

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📅 Original date posted:2018-07-24
📝 Original message:
Dear list, pardon me that I haven't investigated the Lightning implementations in depth yet, but one discussion has made me wonder how you approach the below described situation.
Rene was talking about virtual channels in his article [1]. His motivation was that a company running multiple nodes has to open channels between its own nodes in order to transact between them.
My vision of LN was to allow for much heterogeneity. Not only a company should be able to transact between its own nodes, but also with other entities it has a trust relationship with. Let me give you an example.
Say I trust you unconditionally. Alice asks me to send a satoshi to Bob. I don't have a channel with him, but you do. No channel between us. I receive HTLC from Alice, give you the image. You create HTLC with Bob, using that image. Bob checks - everything is OK. Bob executes.
The problem is source routing. Alice creates the whole payment chain, so she should be aware of our relationship. A solution could be advertising our trust as being a single node or introducing virtual channels as Rene suggests, constantly figuring out our respective balances. Is there a way to do so or do you see any other solution?
I understand the word 'trust' is repulsive, but think of the case with a single company running multiple nodes for whatever reason.
Thanks,
Dima
[1] https://www.rene-pickhardt.de/virtual-payment-channels-for-the-lightning-network-a-lightning-network-improvement-proposal-draft/
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2023-06-09 12:51:01

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📅 Original date posted:2018-07-05
📝 Original message:
Hi Olaoluwa,
I¹m glad we¹re thinking the same direction.
Generally, I think we (the community) worry too much about equilibrium.
There is no really proof that it improves the network. On the other hand,
money being locked in channel is of major issue. Some nodes may be used
mostly for sending payments, whereas others mostly receiving. Therefore,
the distribution of funds in channels should be dictated not by
equilibrium but by nodes' plans to send and receive.
> In this case, equilibrium means being able to recv as much as you can
>send on all your channels.
Now it seems there are two ways to define equilibrium. You have described
one where each node is trying to keep the ability to send and receive at
the same level. I¹ll repeat the above argument, some nodes may be used
mostly for sending payments, whereas others mostly receiving. Therefore,
such definition is unjustified from the individual viewpoint. Another
definition of equilibrium is when a node distributes equally the available
balance amongst the channels it has. Your argument still stands here as
such equilibrium minimises the number of depleted channels.
> The argument here is that by maintaining this balance, one is likely to
>reduce the number of routing failures from failed HTLC forwarding, as the
>channel is equally likely to be able to carry an HTLC in either direction.
If a node has no balance, its channels are depleted. There is nothing we
can do with this. Such nodes are bad for topology and should be
discouraged. Possibly by the autopilot.
> However if a few sources/sinks dominate, then channels may regularly
>become biased requiring more maintenance.
Now you¹re bringing up even more important question. If we had balanced
payments, LN could function without touching blockchain ever again
indefinitely. Skewed traffic is a big problem. Re-balancing won¹t be of
use here because having a fixed nodes¹ balances, there is only a limited
max flow that can be pushed in a particular direction. I believe autopilot
could mitigate the problem. Please, find my argument at the bottom of [1].
[1] https://github.com/lightningnetwork/lnd/issues/677
Best,
Dmytro
From: Olaoluwa Osuntokun <laolu32 at gmail.com>
Date: Tuesday, 3 July 2018 at 22:13
To: Dmytro Piatkivskyi <dmytro.piatkivskyi at ntnu.no>
Cc: "lightning-dev at lists.linuxfoundation.org"
<lightning-dev at lists.linuxfoundation.org>
Subject: Re: [Lightning-dev] Rebalancing argument
Hi Dmytro,
Thanks for bringing this up! Sometime last year when I was at a developer
meetup that cdecker also attended, we briefly discussed a similar
question. We
we're discussing if "active rebalancing" was actually ever really
necessary.
>From my PoV, active rebalancing is rebalancing done for the purpose of
being
able to send/recv a particular payment. On white board, cdecer sketched
out a
similar argument as to Lemma 2 in that paper you linked: namely that there
will
exist an alternative path, therefore active rebalancing isn't necessary.
IMO, in a world pre-AMP, it is indeed necessary. Consider a node Bob that
wishes to receive a payment of 0.5 BTC. Bob has two channels, one with 2
BTC
max capacity, and the other with 1 BTC max capacity. If channel 1 only has
0.2
available for him to receive, and channel 2 only has 0.3 available for him
to
receive, then without active rebalancing, he's unable to receive the
payment.
However, if he completes a circular payment from channel 1 to channel 2
(or the
other way around), then he's able to receive the payment (under ideal
conditions).
In a world post-AMP, then this would seem to no longer apply. Alice the
sender
may be able to utilize the aggregate bandwidth of the network to send
minimally
two payment flows (one 0.2 and one 0.3) to satisfy the payment. As a
result,
active rebalancing isn't needed as payments can be split up to fully
utilize
the payment bandwidth at both the sender and the receiver.
> total balances of nodes in the network define the feasibility of a
>particular
> transaction, not the distribution of balances.
With multi-path payments this is precisely the case!
However, there might be an argument in favor of "passive rebalancing". I
define
passive rebalancing as rebalancing a node carries out independent of
needing to
send/receive payments themselves, in order to ensure an equilibrium state
amongst the available balances of their channels. In this case, equilibrium
means being able to recv as much as you can send on all your channels. The
argument here is that by maintaining this balance, one is likely to reduce
the
number of routing failures from failed HTLC forwarding, as the channel is
equally likely to be able to carry an HTLC in either direction.
One relevant detail w.r.t to the necessity of active rebalancing is the
directionality of payment flows in the network. If payment flows are more
or
less balanced (kinda like the ideal world Byran Vu describes in the post
[1]),
meaning people are sending out as much as they receive (so they get their
paycheck streamed to them over LN, then stream BitFlix w/ that), then it's
possible passive rebalancing isn't really necessary. However if a few
sources/sinks dominate, then channels may regularly become biased requiring
more maintenance.
Also thanks for bringing this paper to my attention! Haven't yet read it in
full yet, but happy to discover that this isn't completes new territory
and is
a problem that's been explored in the existing literature.
[1]:
https://blog.lightning.engineering/posts/2018/05/30/routing.html
<https://blog.lightning.engineering/posts/2018/05/30/routing.html>
-- Laolu
On Sun, Jul 1, 2018 at 5:21 AM Dmytro Piatkivskyi
<dmytro.piatkivskyi at ntnu.no> wrote:
Hi everyone,
I have been working academically on the Lightning network for a while now.
I didn¹t not participate in the list to form my own vision of what it
should be. So please, bear with me if I¹ll be saying nonsense sometimes.
There has been a lot of discussion on sending cycle transactions to
oneself to Œre-balance¹ the network. On LN mailing list
<https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-February/00
1005.html> [1] or numerous
places elsewhere. There has been even a paper suggesting a smart
mechanism to do the re-balancing (see Revive or Liquidity network [2]). My
question is what do we actually get from it? [3] states that the
distribution of funds in channels does not really affect
the network liquidity. I can see cheaper fees or shorter paths if the
network is kept balanced. But don¹t you think that a smart fee strategy
will do the job?
To save your time, [4] explains the gist from [3].
[1]
https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-February/001
005.html
[2]
https://www.reddit.com/r/ethereum/comments/7bse33/were_very_happy_to_announ
ce_the_liquiditynetwork/
[3] https://arxiv.org/abs/1007.0515
[4]
https://medium.com/@dimapiatkivskyi/why-would-you-re-balance-a-payment-netw
ork-796756ad4f31
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Lightning-dev at lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev

2023-06-09 12:50:59

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📅 Original date posted:2018-07-01
📝 Original message:
Hi Rene,
Thanks for your answer!
1. The Lightning network operates under different assumptions, that is true. However, the difference is minor in terms of the issue posed. The premise for the quoted statement is that taking fees changes the nodes’ balances, therefore selected paths affect the liquidity. In the Lightning network fees are very small, so the change in liquidity may be negligible. Moreover, intermediate nodes gain in fees, which only increases the liquidity.
2.A. It is too early to speculate where the privacy requirements will settle down. Flare suggests a mechanism of sharing the infrastructure view between nodes, possibly sharing weights. As the network grows routing will become more difficult, however we don’t know yet to which extent. It may organise itself in ‘domains’, so when we send a payment we know to which domain we are sending to, knowing the path to it beforehand. The point is we don’t know yet, so we can’t speculate.
2.B. That is surely an interesting aspect. HTLC locks temporarily downgrade the network liquidity. Now the question is how it changes the order of transactions and how that order change affects the transaction feasibility. Does it render some transactions infeasible or just defers them? It definitely needs a closer look.
Yet the question remains — are there obvious advantages of cycle transactions over a smart fee/routing system? In any sense. Path lengths, for example. To answer that I am going to run a simulation, but also would appreciate your opinions.
Best,
Dmytro
From: René Pickhardt <r.pickhardt at googlemail.com<mailto:r.pickhardt at googlemail.com>>
Date: Sunday, 1 July 2018 at 13:59
To: Dmytro Piatkivskyi <dmytro.piatkivskyi at ntnu.no<mailto:dmytro.piatkivskyi at ntnu.no>>
Cc: lightning-dev <lightning-dev at lists.linuxfoundation.org<mailto:lightning-dev at lists.linuxfoundation.org>>
Subject: Re: [Lightning-dev] Rebalancing argument
Hey Dmytro,
thank your for your solid input to the discussion. I think we need to consider that the setting in the lightning network is not exactly comparable to the one described in the 2010 paper.
1st: the paper states in section 5.2: "It appears that a mathematical analysis of a transaction routing model where intermediate nodes charged a routing fee would require an entirely new approach since it would invalidate the cycle-reachability relation that forms the basis of our results."
Since we have routing fees in the lightning network to my understanding the theorem and lemma you quoted in your medium post won't hold.
2nd: Even if we neglect the routing fees and assume the theorem still holds true we have two conditions that make the problem way more dynamic:
A) In the lightning network we do not know the weights of the directed edges. (only the sum of two opposing edges) So while theoretically the flow in the network will only depend on the liquidity of the nodes I guess in practice well balanced channels will increase the probability to actually find a working route.
B) I believe the HTLCs create a situation where funds are being locked up while routing takes place and thus have an impact to the entire flow of the network. While Alice searches for a route for her payment a proper route could be blocked do to the fact that Bob is using it currently. Since the funds of Bob have not arrived Alice might also not be able to find a different route.
However those scientific results are a strong call for Atomic Multipath Payments. I personally think they are also a strong call for splicing since this allows to easilly increase the flow of the network by updating a channel (athough you might argue that following the paper this could be achieved by just creating a new channel)
best Rene
On Sun, Jul 1, 2018 at 12:21 PM Dmytro Piatkivskyi <dmytro.piatkivskyi at ntnu.no<mailto:dmytro.piatkivskyi at ntnu.no>> wrote:
Hi everyone,
I have been working academically on the Lightning network for a while now. I didn’t not participate in the list to form my own vision of what it should be. So please, bear with me if I’ll be saying nonsense sometimes.
There has been a lot of discussion on sending cycle transactions to oneself to ‘re-balance’ the network. On LN mailing list<https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-February/001005.html> [1] or numerous places elsewhere. There has been even a paper suggesting a smart mechanism to do the re-balancing (see Revive or Liquidity network [2]). My question is what do we actually get from it? [3] states that the distribution of funds in channels does not really affect the network liquidity. I can see cheaper fees or shorter paths if the network is kept balanced. But don’t you think that a smart fee strategy will do the job?
To save your time, [4] explains the gist from [3].
[1] https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-February/001005.html
[2] https://www.reddit.com/r/ethereum/comments/7bse33/were_very_happy_to_announce_the_liquiditynetwork/
[3] https://arxiv.org/abs/1007.0515
[4] https://medium.com/@dimapiatkivskyi/why-would-you-re-balance-a-payment-network-796756ad4f31
_______________________________________________
Lightning-dev mailing list
Lightning-dev at lists.linuxfoundation.org<mailto:Lightning-dev at lists.linuxfoundation.org>
https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev
--
www.rene-pickhardt.de<http://www.rene-pickhardt.de/>
<http://www.beijing-china-blog.com/>
Skype: rene.pickhardt
mobile: +49 (0)176 5762 3618
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2023-06-09 12:50:59

- reply

📅 Original date posted:2018-07-01
📝 Original message:
Hi everyone,
I have been working academically on the Lightning network for a while now. I didn't not participate in the list to form my own vision of what it should be. So please, bear with me if I'll be saying nonsense sometimes.
There has been a lot of discussion on sending cycle transactions to oneself to 're-balance' the network. On LN mailing list<https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-February/001005.html> [1] or numerous places elsewhere. There has been even a paper suggesting a smart mechanism to do the re-balancing (see Revive or Liquidity network [2]). My question is what do we actually get from it? [3] states that the distribution of funds in channels does not really affect the network liquidity. I can see cheaper fees or shorter paths if the network is kept balanced. But don't you think that a smart fee strategy will do the job?
To save your time, [4] explains the gist from [3].
[1] https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-February/001005.html
[2] https://www.reddit.com/r/ethereum/comments/7bse33/were_very_happy_to_announce_the_liquiditynetwork/
[3] https://arxiv.org/abs/1007.0515
[4] https://medium.com/@dimapiatkivskyi/why-would-you-re-balance-a-payment-network-796756ad4f31
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