netdev - Re: [PATCH v6 net-next 2/2] tcp: Add Redundant Data Bundling (RDB)

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Message-ID: <1457990140.31401.20.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Mon, 14 Mar 2016 14:15:40 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Bendik Rønning Opstad <bro.devel@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Yuchung Cheng <ycheng@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	Andreas Petlund <apetlund@...ula.no>,
	Carsten Griwodz <griff@...ula.no>,
	Pål Halvorsen <paalh@...ula.no>,
	Jonas Markussen <jonassm@....uio.no>,
	Kristian Evensen <kristian.evensen@...il.com>,
	Kenneth Klette Jonassen <kennetkl@....uio.no>
Subject: Re: [PATCH v6 net-next 2/2] tcp: Add Redundant Data Bundling (RDB)

On Thu, 2016-03-03 at 19:06 +0100, Bendik Rønning Opstad wrote:
> Redundant Data Bundling (RDB) is a mechanism for TCP aimed at reducing
> the latency for applications sending time-dependent data.
> 
> Latency-sensitive applications or services, such as online games,
> remote control systems, and VoIP, produce traffic with thin-stream
> characteristics, characterized by small packets and relatively high
> inter-transmission times (ITT). When experiencing packet loss, such
> latency-sensitive applications are heavily penalized by the need to
> retransmit lost packets, which increases the latency by a minimum of
> one RTT for the lost packet. Packets coming after a lost packet are
> held back due to head-of-line blocking, causing increased delays for
> all data segments until the lost packet has been retransmitted.

Acked-by: Eric Dumazet <edumazet@...gle.com>

Note that RDB probably should get some SNMP counters,
so that we get an idea of how many times a loss could be repaired.

Ideally, if the path happens to be lossless, all these pro active
bundles are overhead. Might be useful to make RDB conditional to
tp->total_retrans or something.