From alancarb at googlemail.com  Tue Nov 21 09:07:05 2017
From: alancarb at googlemail.com (Alan Carbery)
Date: Tue, 21 Nov 2017 09:07:05 -0000
Subject: [Lightning-dev] Bi-directional or uni-directional?
In-Reply-To: <87bmjw2uxk.fsf@rustcorp.com.au>
References: <022101d36228$8d7e60c0$a87b2240$@gmail.com>
	<87bmjw2uxk.fsf@rustcorp.com.au>
Message-ID: <025e01d362a8$1a804cc0$4f80e640$@gmail.com>

Thanks for the response Rusty. 

I think what's confusing me is that the tutorials all show an example where
Alice and Bob each put 5BTC into the funding transaction.  However, in the
spec open_channel has the funding_satoshis attribute for this purpose while
accept_channel does not.  Does this mean that each channel is funded by one
party only but they can make payments in both directions (assuming that some
initial payments are made by the party funding the channel)?  Any idea about
the rationale for one-sided channel funding?

Regards,
Alan

-----Original Message-----
From: Rusty Russell [mailto:rusty at rustcorp.com.au] 
Sent: 21 November 2017 03:05
To: Alan Carbery <alancarb at googlemail.com>;
lightning-dev at lists.linuxfoundation.org
Subject: Re: [Lightning-dev] Bi-directional or uni-directional?

Alan Carbery via Lightning-dev <lightning-dev at lists.linuxfoundation.org>
writes:
> Hi,
>
> All the tutorials that I've read about Lightning describe 
> bi-directional channels.  However, reading through the draft RFC I'm 
> wondering if it's uni-directional only.  Can anyone clarify if this is 
> the case and if so then is there a reason for not doing bi-directional 
> channels in the first release?

No, they're bidirectional!  It's just that each side sends a batch of
updates followed by a commitment, then the other side replies with an ack.
Both sides can do that independently and it all works out.

Hope that helps!
Rusty.