http://www.ieng.com/univercd/cc/td/doc/product/software/ioss390/ios390cg/cgnet.h tm#xtocid35597
Maximizing Throughput
Throughput can be maximized by sending data packets that are as large as the MTU for the local network. TCP uses the Maximum Segment Size (MSS) option to regulate the size of TCP segments transmitted on a TCP connection, which in turn determines the maximum size of packets generated by IP. Generally, sending the largest TCP segment possible is more efficient because the total number of segments transmitted is reduced. However, if the communicating hosts are not on the same network (or subnetwork), intervening gateways might need to fragment the packets, which can be less efficient than sending smaller segments in the first place.
The MSSOPT parameter controls when the local TCP uses the MSS TCP option to increase the size of TCP segments it is willing to receive (the default is the MTU). If permitted, TCP increases its receive segment size to a value that lets the remote TCP send segments that are optimal for the local network and will never transmit a segment larger than that advertised by the remote TCP.
Next to NEVER, MSSOPT(SUBNET) is the most restrictive option because both hosts must be on the same subnet. If the network is not a subnet, or all subnets comprising the local network use the same MTU, or fragmentation is not a concern, MSSOPT(NET) should be used. Otherwise, use MSSOPT(ALWAYS).
also....
Maximum Receive Segment Size
The MSSDEF parameter determines what the maximum receive segment size can be if the MSSOPT parameter does not permit using the optimum value for the local network. This permits using a value larger than the Internet-wide default and smaller than the MTU for the local network. For example, if several local area networks are interconnected by a wide area network whose MTU is smaller than that of the local area networks, MSSDEF should be set to the MTU of the wide area network. When used with the appropriate MSSOPT parameter, TCP can use larger segments while avoiding fragmentation.
The MSSDEF value is specified in terms of the IP packet size and not the actual TCP segment size. In other words, the value specified for MSSDEF should be the largest network packet, excluding the network header but including the normal TCP and IP headers, that can be generated with a maximum size TCP segment.
Just happen to run across this while searching for something else. What are the MSSOPT and MSSDEF parameters? - never heard of them before. Wonder if there is a similar setting for the microsoft tcp/ip stack?
[This message has been edited by Mystic (edited 11-21-2000).]
