netdev - [PATCH net-next 1/3] ipv4: Raise tcp PMTU probe mss base size

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Date:	Fri, 13 Feb 2015 16:16:43 +0800
From:	Fan Du <fan.du@...el.com>
To:	davem@...emloft.net
Cc:	netdev@...r.kernel.org, fengyuleidian0615@...il.com
Subject: [PATCH net-next 1/3] ipv4: Raise tcp PMTU probe mss base size

Quotes from RFC4821 7.2.  Selecting Initial Values

   It is RECOMMENDED that search_low be initially set to an MTU size
   that is likely to work over a very wide range of environments.  Given
   today's technologies, a value of 1024 bytes is probably safe enough.
   The initial value for search_low SHOULD be configurable.

Moreover, set a small value will introduce extra time for the search
to converge. So set the initial probe base mss size to 1024 Bytes.

Signed-off-by: Fan Du <fan.du@...el.com>
---
 include/net/tcp.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 8d6b983..7b57e5b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -65,7 +65,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
 #define TCP_MIN_MSS		88U

 /* The least MTU to use for probing */
-#define TCP_BASE_MSS		512
+#define TCP_BASE_MSS		1024

 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 #define TCP_FASTRETRANS_THRESH 3
-- 
1.7.1

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