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TCP Optimizer Help
Adjusting IP MTU, TCP MSS, and PMTUD on Windows and Sun Systems
* Maximize MTU size
In 1 Gbps or 10 Gbps environment, the use of Jumbo Frame is suggested.
* Enable TCP Window Scaling option (refer to RFC 1323 for details)
The key is to use the maximum window size possible and enable Selective Acknowledgment.
* Ensure the NIC of hosts (such as servers, PC) support TSO (TCP Segmentation Offload) and RSO (Receive Segmentation Offload) and are enabled. There is some reading about such in TCP implementation - Linux manual
Using TTCP to test throughput
A ttcp (Test TCP) can be used as a test tool and use its UDP test to validate that the servers in question can achieve certain throughput number. Following is sample ttcp command to test 10 Gbps throughput.
1. UNIX/Linux machine
On receiver use:
ttcp -r -u -p55555 -l8192 -n640000 -b131072 -D -tm > /dev/null
On sender use:
dd if=/dev/zero bs=1M count=5000 | ttcp -t -u -p55555 -l8192 -n640000 -b131072 -D -tm (ip address of receiver)
This will transfer 5000MB via UDP and if 10GbE is operating correctly, one would get a transfer rate close to 1000MB/s.
If the rate is substantially lower than expected, look for errors on the server, switch ports etc. Then clear counters on interfaces and look at the counters after a test.
Once its established that the rate is as expected, switch to TCP by removing the '-u' from the ttcp options to make it use TCP.
2. Windows machine
Check out the following link for illustration.
Using Test TCP (TTCP) to Test Throughput