The performance of Microsoft LAN Manager networks using TCP/IP can often be increased significantly by carefully tuning several stack parameters:
- tcpsegmentsize (the maximum size of a single TCP segment)
- tcpwindowsize (the amount of data a receiving TCP stack can buffer)
- nbsessions (the maximum number of NetBIOS sessions available)
- tcpconnections (the maximum number of TCP connections available)
For optimum performance, tcpsegmentsize should be the size of the MTU (maximum transfer unit) the media can handle, minus all headers up through the IP layer. LAN Manager TCP/IP allows sizes of 1450 bytes or less to be assigned to this parameter.
Also for optimum performance, tcpwindowsize should typically be as large as possible, in increments of tcpsegmentsize. Increasing tcpwindowsize, however, requires more memory, which can be a problem under MS-DOS. The TCP driver must load into a single 64K segment of memory. The driver must be able to buffer "tcpwindowsize" bytes of data on EACH tcpconnection, so the tcpwindowsize and tcpconnections values must be balanced against each other to achieve the best overall performance and connectivity.
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