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

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Date:	Tue, 15 Mar 2016 11:09:18 -0700
From:	Yuchung Cheng <ycheng@...gle.com>
To:	Rick Jones <rick.jones2@....com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Bendik Rønning Opstad <bro.devel@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	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 Mon, Mar 14, 2016 at 6:04 PM, Rick Jones <rick.jones2@....com> wrote:
>
> On 03/14/2016 02:15 PM, Eric Dumazet wrote:
>>
>> 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.
>
>
> And some idea of the duplication seen by receivers, assuming there isn't already a counter for such a thing in Linux.

We sort of track that in the awkwardly named LINUX_MIB_DELAYEDACKLOST



>
> happy benchmarking,
>
> rick jones
>
>
>>
>> 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.
>>
>>
>