From fabrice.drouin at acinq.fr Thu Jan 3 22:52:15 2019 From: fabrice.drouin at acinq.fr (Fabrice Drouin) Date: Thu, 3 Jan 2019 23:52:15 +0100 Subject: [Lightning-dev] Quick analysis of channel_update data In-Reply-To: References: <87ef9veztc.fsf@gmail.com> Message-ID: Follow-up: here's more detailed info on the data I collected and potential savings we could achieve: I made hourly routing table backups for 12 days, and collected routing information for 17 000 channel ids. There are 130 000 different channel updates :on average each channel has been updated 8 times. Here, ?different? means that at least the timestamp has changed, and a node would have queried this channel update during its syncing process. But only 18 000 pairs of channel updates carry actual fee and/or HTLC value change. 85% of the time, we just queried information that we already had! Adding a basic checksum (4 bytes for example) that covers fees and HTLC min/max value to our channel range queries would be a significant improvement and I will add this the open BOLT 1.1 proposal to extend queries with timestamps. I also think that such a checksum could also be used - in ?inventory? based gossip messages - in set reconciliation schemes: we could reconcile [channel id | timestamp | checksum] first Cheers, Fabrice