SUMMARY: TCP receive window

From: Chuck <>
Date: Tue May 03 2005 - 20:17:54 EDT
Chuck <> wrote:
|Folks, I ran a Network Appliance (aka NetApp) netdiag command
|and it says that I should adjust a TCP parameter on my Solaris
|box. I would like to increase my TCP receive window to 32768 
|bytes, per NetApp but I can not seem to see what Solaris name 
|adjusts this value. I am pretty sure it's tcp_recv_hiwat value, 
|but wanted to check here 1st. The list is below. I will summarize.

Thanks everyone below and those who may respond in the future.

Several folks did a "yep that's it" while some said to go w/ 65535
bytes for the TCP/UDP receive and send windows.  Blake G. gave me what
I was looking for the dynamic ndd and the static lines of that go in
/etc/system.  I am including his message below.

I don't like to add little rc files as in my opinion, network 
parameters need set as early as possible.  Especially, speed and
duplex for a net interface.  So, I usually, set them in /etc/system
AND until the next reboot use an ndd to adjust the in memory
value.  The trick is to make sure you get the /etc/system values
right as you may think you set something, but ...


Thanks again ...

From: "Golliher, Blake" <> 
From: "John Dewey" <> 
From: "Michael Horton" <> 
From: "Eric Lewandowski" <> 
From: "Murdock, Matt" <> 
From:  "Terry Gardner" <> 

Subject: RE: TCP receive window  
Date: Tue, 3 May 2005 13:22:37 -0700 
From: "Golliher, Blake"
To: "Chuck" <> 

Yes, that's the correct variable to tune.  NetApp (and Sun) agree
that you can set this as high at 65535.  Here are two methods you can
use to configure the network. 

You can place the following items in your /etc/rc2.d/S99netperf file 
and run the script (or reboot):

    ndd -set /dev/udp udp_recv_hiwat 65535
    ndd -set /dev/udp udp_xmit_hiwat 65535
    ndd -set /dev/tcp tcp_recv_hiwat 65535
    ndd -set /dev/tcp tcp_xmit_hiwat 65535
    ndd -set /dev/ge instance 0
    ndd -set /dev/ge adv_pauseTX 1
    ndd -set /dev/ge adv_pauseRX 1
    ndd -set /dev/ge adv_1000autoneg_cap 1
    ndd -set /dev/ge adv_1000fdx_cap 1

OR add the following items to the /etc/system file and reboot the
database server:

    set ndd:udp_recv_hiwat=65535
    set ndd:udp_xmit_hiwat=65535
    set ndd:tcp_recv_hiwat=65535
    set ndd:tcp_xmit_hiwat=65535
    set ndd:instance=0
    set ndd:adv_pauseTX=1
    set ndd:adv_pauseRX=1
    set ndd:adv_1000autoneg_cap=1
    set ndd:adv_1000fdx_cap=1

The maximum UDP socket datagram size in bytes. The default value is
8192. The maximum value is 65535.

The maximum UDP socket receive buffer size in bytes. The default value
is 8192. The maximum value is 65535.

The default receive window size in bytes. The default value is 24576.
The maximum value is 1073741824.

The default send window size in bytes. The default value is 16384. The
maximum value is 1073741824.

Specify an entry for each device instance in your system. The 
succeeding lines will apply to this device instance.

To enable transmit flow control on the device, send pause frames
to its link partner, set this parameter to 1.  Enabling flow
control reduces the possibility that one interface will overrun 
the other.

To enable receive flow control on the device, receive pause
frames from its link partner, set this parameter to 1. Gigabit
Ethernet flow control settings are wholly dependent on the link
partner, whether you're direct connected or connected via a 
switch. Certain switches may have receive flow control disabled
by default.

To enable auto negotiation, set this parameter to 1. This means
that the adapter will communicate with its link partner to determine a 
compatible network speed, duplex mode, and flow control capability.
This setting is configuration dependent. Some devices, switches and/
or controllers, do not support auto negotiation, others will not let
you disable it.

adv_1000fdx_cap  To enable full duplex capability, bidirectional
simultaneous data transfer, set this parameter to 1.

Repeat the last 4 items above for every Gigabit Ethernet adapter in the
system, changing the instance number in each case.

Hope that helps! =)
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Received on Tue May 3 20:18:22 2005

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