net: TCP thin dupack

This patch enables fast retransmissions after one dupACK for
TCP if the stream is identified as thin. This will reduce
latencies for thin streams that are not able to trigger fast
retransmissions due to high packet interarrival time. This
mechanism is only active if enabled by iocontrol or syscontrol
and the stream is identified as thin.

Signed-off-by: Andreas Petlund <apetlund@simula.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index f147310d9af4..2571a62d923e 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -499,6 +499,18 @@ tcp_thin_linear_timeouts - BOOLEAN
         Documentation/networking/tcp-thin.txt
         Default: 0
 
+tcp_thin_dupack - BOOLEAN
+        Enable dynamic triggering of retransmissions after one dupACK
+        for thin streams. If set, a check is performed upon reception
+        of a dupACK to determine if the stream is thin (less than 4
+        packets in flight). As long as the stream is found to be thin,
+        data is retransmitted on the first received dupACK. This
+        improves retransmission latency for non-aggressive thin
+        streams, often found to be time-dependent.
+        For more information on thin streams, see
+        Documentation/networking/tcp-thin.txt
+        Default: 0
+
 UDP variables:
 
 udp_mem - vector of 3 INTEGERs: min, pressure, max