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Administrator's Reference

TCPWINDOWSIZE

Specifies, in kilobytes, the amount of receive data that can be buffered at one time on a TCP/IP connection. The sending host cannot send more data until it receives an acknowledgment and a TCP receive window update. Each TCP packet contains the advertised TCP receive window on the connection. A larger window lets the sender continue sending data, and may improve communication performance, especially on fast networks with high latency.

Notes:

  1. To improve backup performance, increase the TCPWINDOWSIZE on the server. To improve restore performance, increase the TCPWINDOWSIZE on the client.

  2. The TCP window acts as a buffer on the network. It is not related to the TCPBUFFSIZE option nor to the send and receive buffers allocated in client or server memory.

  3. A window size larger than the buffer space on the network adapter might degrade throughput due to resending packets that were lost on the adapter.

  4. The maximum TCPWINDOWSIZE supported under Windows NT 3.5, 3.51, and 4.0 is 65535 (64K - 1) bytes. Using a TCPWINDOWSIZE that creates a request for a larger window size results in the default receive window, which could be much smaller than expected. Therefore, in these environments the TCPWINDOWSIZE value should not be greater than 63.

  5. Windows 2000 provides a larger TCP receive window size when communicating with hosts that also provide this support, known as RFC1323. In these environments, a value greater than 63 may be useful.

Syntax

>>-TCPWindowsize--kilobytes------------------------------------><
 
 

Parameters

kilobytes
Specifies the size you want to use, in kilobytes, for the TCP/IP sliding window for your client node. You can specify a value from 0 to 2048. If you specify 0, the server uses the default window size set by the operating system. Values from 1 to 2048 indicate that the window size is in the range of 1KB to 2MB.

Examples

tcpwindowsize 8


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