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I understand that as part of a lightning invoice routing hints can be provided that provide information about private channels that can be used to reach the destination. I believe these are the r fields in BOLT 11. I also found a link to the LND implementation that appears to only include hints for channels that have sufficient balance to route the entire amount by themselves. So this means that at least for LND a routing hint implies a certain minimum channel balance.

I've got the following questions

  • is this specific to LND or do other implementations do the same?
  • if so, it could make sense to provide routing hints even for public channels, just to signal that they have sufficient balance. Is this allowed and do implementations do this?
  • if a certain destination wants to receive 100 satoshis and has 10 private channels that have a remote balance of 99 satoshis each, does this mean no routing hints will be provided, because no single channel can route the entire amount by itself, so the payment will fail, even though the payment is feasible using a multi path payment?

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is this specific to LND or do other implementations do the same?

Other implementations also send these.

if so, it could make sense to provide routing hints even for public channels, just to signal that they have sufficient balance. Is this allowed and do implementations do this?

It might make sense, I've thought about ideas where you could signal which channels you'd prefer payment through even if they're public. From the senders point of view they wouldn't be able to tell what is most convenient for the recipient, so this could help alleviate issues.

if a certain destination wants to receive 100 satoshis and has 10 private channels that have a remote balance of 99 satoshis each, does this mean no routing hints will be provided, because no single channel can route the entire amount by itself, so the payment will fail, even though the payment is feasible using a multi path payment?

LND tries to provide at least 20 channels to facilitate payment to a private/hard to find node. If the number of high quality channels is lower than 20, LND will select as many low quality channels as possible (without doxxing other private nodes) to meet that 20 channel requirement.

To simplify, it will provide all those 99 sat channels.

Another idea of note - all hophints are designed to do is add more edges to the senders's graph, in case their graph doesn't have the information required to route to the recipient.

I wrote a short blog about hophints a few months back, maybe you'll find it interesting!

https://write.as/arshbot/everything-you-need-to-know-about-hop-hints-in-the-lightning-network

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  • thanks for your answer! Somehow I missed the second pass in the source file that I linked although it's very clear now. Sorry for that. So to summarize: no, routing hints do not with certainty imply a certain minimum channel balance, however the first routing hints are more likely to have sufficient balance, because those are added first. Interesting blog post.
    – Martin
    Feb 28 at 19:14

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