Re: [RFC] multi_ack protocol v2

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Oct 27, 2005, 10:54 UTC
Message-ID: <Pine.LNX.4.63.0510271248590.3663@wbgn013.biozentrum.uni-wuerzburg.de>
In-Reply-To: <17248.39333.181379.615274@cargo.ozlabs.ibm.com>

Hi,

On Thu, 27 Oct 2005, Paul Mackerras wrote:

Show 9 quoted lines

> Johannes Schindelin writes:
> 
> > after thinking about my earlier approach, I think there's a better, less 
> > intrusive, and all in all just simpler approach:
> 
> How many round-trips does it take?  When you're on the other side of
> the Pacific from the server you care about round-trips. :)  One of the
> nice things about rsync is that it does everything with only 1.5
> round-trips.

The plan is to reuse the existing framework. It sends 32 "have" messages, then a flush, then again 32 "have" messages, flush again, then reads all answers until a "NAK". The last 3 steps are repeated over and over again.

That means that there are always at least 32 "have" messages on the wire (which is described in the source code as "one window ahead"), i.e. it is about 32x faster than simple "have" -> "NAK/ACK" handshakes.

Ciao, Dscho