2 files changed, 10 insertions, 4 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 3e0c017e7877..90ed78110fd4 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -102,9 +102,15 @@ inet_peer_gc_maxtime - INTEGER
 TCP variables: 
 
 tcp_abc - INTEGER
-        Controls Appropriate Byte Count defined in RFC3465. If set to
-        0 then does congestion avoid once per ack. 1 is conservative
-        value, and 2 is more agressive.
+        Controls Appropriate Byte Count (ABC) defined in RFC3465.
+        ABC is a way of increasing congestion window (cwnd) more slowly
+        in response to partial acknowledgments.
+        Possible values are:
+                0 increase cwnd once per acknowledgment (no ABC)
+                1 increase cwnd once per acknowledgment of full sized segment
+                2 allow increase cwnd by two if acknowledgment is
+                  of two segments to compensate for delayed acknowledgments.
+        Default: 0 (off)
 
 tcp_syn_retries - INTEGER
         Number of times initial SYNs for an active TCP connection attempt
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 111ff39a08c5..159fa3f1ba67 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -89,7 +89,7 @@ int sysctl_tcp_frto;
 int sysctl_tcp_nometrics_save;
 
 int sysctl_tcp_moderate_rcvbuf = 1;
-int sysctl_tcp_abc = 1;
+int sysctl_tcp_abc;
 
 #define FLAG_DATA               0x01 /* Incoming frame contained data.          */
 #define FLAG_WIN_UPDATE         0x02 /* Incoming ACK was a window update.       */