From jim.posen at gmail.com Thu Mar 1 14:45:16 2018 From: jim.posen at gmail.com (Jim Posen) Date: Thu, 1 Mar 2018 09:45:16 -0500 Subject: [Lightning-dev] Pinging a route for capacity Message-ID: My understanding is that the best strategy for choosing a route to send funds over is to determine all possible routes, rank them by estimated fees based on channel announcements and number of hops, then try them successively until one works. It seems inefficient to me to actually do a full HTLC commitment handshake on each hop just to find out that the last hop in the route didn't have sufficient remaining capacity in the first place. Depending on how many people are using the network, I could also forsee situations where this creates more payment failures because bandwidth is locked up in HTLCs that are about to fail anyway. One idea that would likely help is the ability to send a ping over an onion route asking "does every hop have capacity to send X msat?" Every hop would forward the onion request if the answer is yes, or immediately send the response back up the circuit if the answer is no. This should reveal no additional information about the channel capacities that the sender couldn't determine by sending a test payment to themself (assuming they could find a loop). Additionally, the hops could respond with the latest fee rate in case channel updates are slow to propagate. The main benefit is that this should make it quicker to send a successful payment because latency is lower than sending an actual payment and the sender could ping all possible routes in parallel, whereas they can't send multiple payments in parallel. The main downside I can think of is that, by the same token, it is faster and cheaper for someone to extract information about channel capacities on the network with a binary search. -jimpo -------------- next part -------------- An HTML attachment was scrubbed... URL: