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TTM Network Administration

Manually Configuring TCP Window Size

Overview

The TCP window is a configurable quantity of data (in KB) that this TTM instance can receive in a single receive buffer. After sending the configured amount of data, the TTM peer waits for an acknowledgement (ACK) from this TTM instance. If the TTM peer does not receive an ACK, it begins queuing the data.

  • For Remote Host Daemons, you can configure the size of the TCP window using the tcp_window_size parameter in the <General> section of the ttmd.cfg file.
  • For Remote Clients, you can configure the size of the TCP window using the tcp_window_size parameter in the <Daemon> section of <proxy> section in the ttmd.cfg file.

Recommendations

If you experience a large delay in your network path, TT recommends that you increase the size of the TCP window size. To determine the appropriate TCP window size, use the following formula:

TCP window size = (Bandwidth of the link in bps) * (round trip time in seconds) / 8192

Example:

A customer connects two networks over a link that has a 3 Mbps link with a 0.4 second (400 milliseconds) round trip time.

Plugging these values into the formula, one gets:

(3145728) * (.4) / 8192 = 153.6

The customer sets tcp_window_size to 154.

TCP Window Size Parameter

TCP Window Size Parameter
ParameterDescription
tcp_window_size

Sets the quantity of data (in KB) that this TTM instance can receive in a single receive buffer. After sending the configured amount of data, the TTM peer waits for an acknowledgement (ACK) from this TTM instance. If the TTM peer does not receive an ACK, it begins queuing the data.

You must use a whole number to set a value for tcp_window_size.

By default ttmd.cfg does not install with the tcp_window_size parameter. If this parameter is missing or set to an invalid value, TTM behaves as if the parameter is set to 64.

Configuring TCP Window Size for Remote Host Daemons

You configure tcp_window_size in ttmd.cfg.

To configure the TCP window size:

  1. Using Notepad, open the ttmd.cfg, located in <root drive>:ttconfig.
  2. In the <General> section, edit the tcp_window_size parameter. If the parameter does not exist, add it.
  3. Save and then close the file.
  4. Stop and restart TTM.
Note

To configure the TCP window size for Gateways, use the tcp_window_size parameter in the Gateway’s hostinfo.cfg file (using the same formula from Recommendations). The ttmd.cfg tcp_window_size parameter does not affect Gateways.

Configuring TCP Window Size for Remote Clients

You configure tcp_window_size in ttmd.cfg.

To configure the TCP window size:

  1. Using Notepad, open the ttmd.cfg file, located in <root drive>:ttconfig.
  2. In the <Daemon> section of the <Proxy> section, edit the tcp_window_size parameter. If the parameter does not exist, add it.
  3. Save and then close the file.
  4. Stop and restart TTM.
Note

To configure the TCP window size for Gateways, use the tcp_window_size parameter in the Gateway’s hostinfo.cfg file (using the same formula from Recommendations). The ttmd.cfg tcp_window_size parameter does not affect Gateways.