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If the goal of the lightning network is to route payments as cheap as possible (i know this is an assumption and maybe not everyone agrees), why wouldn't it be a good idea to just drop the percentage fee? A fee in general is necessary to prevent spamming, that is why no fee wouldn't work. Is that assumption correct?

Is that assumption correct?

Rene points out, that fees are not preventing spammers from spamming the network.

That leaves the question: Why not drop the percentage and keep the base fee?

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    With the current design of the lightning network fees do not prevent any spam at all. The price for setting up htlcs in remote channels is independent of the fee schedule only paid if the htlcs settle. An attacker who wants to spam will just not settle the HTLCs and thus will never pay any fee – Rene Pickhardt Aug 26 '21 at 20:14
  • thanks for clarifying this - will update my question –  Aug 27 '21 at 09:07

2 Answers2

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The lightning network is still young, so I don't think there is an absolute consensus amongst users on what the optimal fee policy is. That said, one consideration could be:

When deciding your lightning node's fee policy, one consideration is simply liquidity allocation. Generally speaking, channels that are well balanced will be more useful than channels that are unbalanced (ie, all of the funds sitting on one side). Routing a payment means pushing the channel balance around, so if someone pushes payments that unbalance your channel(s), you may want some compensation, to help cover any potential costs of rebalancing your channel.

chytrik
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  • thanks - this could answer the question why any fees at all. but i can get the needed funds by setting a base fee and not a percentage fee –  Aug 27 '21 at 08:39
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I think the main reason that speaks agains dropping the fee rate and keeping the base fee instead is that finding optimal payment flows would become an NP-hard problem for nodes who wish to make a payment (if they try to find a cheap solution which I assume anyone would like to do)

If however we keep the fee rate and drop the base fee the problem to find the cheapest payment flow through the market of offered channels becomes a computationally much simpler problem.

Rene Pickhardt
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  • why would using something variable be better than using something fixed? –  Aug 31 '21 at 16:11