netdev - Re: [PATCHv4 net-next 1/3] ipv4: Raise tcp PMTU probe mss base size

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Date:	Tue, 3 Mar 2015 11:52:39 -0500
From:	John Heffner <johnwheffner@...il.com>
To:	Fan Du <fan.du@...el.com>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>,
	Fan Du <fengyuleidian0615@...il.com>
Subject: Re: [PATCHv4 net-next 1/3] ipv4: Raise tcp PMTU probe mss base size

On Tue, Mar 3, 2015 at 4:19 AM, Fan Du <fan.du@...el.com> wrote:
> 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
>

Acked-by: John Heffner <johnwheffner@...il.com>
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