From rusty at rustcorp.com.au  Wed Dec 16 00:04:00 2015
From: rusty at rustcorp.com.au (Rusty Russell)
Date: Wed, 16 Dec 2015 10:34:00 +1030
Subject: [Lightning-dev] Transaction time
In-Reply-To: <CAPxRocyFsatevudZfugenjxMf3J4qYHLVn41+O4o6Uj8XyzWqw@mail.gmail.com>
References: <CAPxRocyFsatevudZfugenjxMf3J4qYHLVn41+O4o6Uj8XyzWqw@mail.gmail.com>
Message-ID: <87a8pbxnrj.fsf@rustcorp.com.au>

Denis Gorbachev <denis.d.gorbachev at gmail.com> writes:
> Assuming a simple case of "Consumer - Relay - Provider" (2 hops), how long
> should it take for provider to receive the payment?

Assuming established channels already (assuming CPU is instant, so we're
just paying for network latency):

Consumer offers Relay a contract:
        C -> R: update_add_htlc
        R -> C: update_accept
        C -> R: update_signature
        R -> C: update_complete*

Relay offers Provider a contract:
        R -> P: update_add_htlc
        P -> R: update_accept
        R -> P: update_signature
        P -> R: update_complete*

Provider closes contract with relay:
        P -> R: update_fulfill_htlc
        R -> P: update_accept
        P -> R: update_signature
        R -> P: update_complete*

Relay closes contract with Client:
        R -> C: update_fulfill_htlc
        C -> R: update_accept
        R -> C: update_signature
        C -> R: update_complete*

You don't need to wait for the update_complete packets to arrive, so
that works out to 3 RTTs per hop.  You might expect up to 10 hops in a
large lightning network, so 30 RTTs.

I'm in Australia, and my bitcoin node latency averages 330ms (ouch!).
So that would be 10 seconds.

Hope that helps!
Rusty.