Testing TCP Transmission

Your target must be able to transmit TCP packets reliably, and with acceptable throughput. You should also validate the driver with various TCP window sizes.

Transmit TCP Test using NDIT

This test measures the capacity of the target to send packets to a server located on the test station. To optimize performance, the value of NET_TCP_CFG_TX_WIN_SIZE_OCTET in net_cfg.h should be set to the number of transmit descriptors multiplied by 1460 bytes. The TCP Transmit Window Size should be set to the target's number of transmit buffers multiplied by 1460 bytes.

Select the TCPc test tab in the NDIT main window. The TCP transmit test panel appears.

There are four options for the TCP transmit test:

Buffer Size

The length of the buffer to transmit.

Tx Window Size

The size of the transmit socket window on the target host.

Rx Window Size

The size of the receive socket window on the test station.

Test Duration

Located in the General Options tab.

Expected results

• Highest throughput possible

  Although it is difficult to estimate the achievable throughput with a particular device, it is possible to compare with other drivers sharing roughly the same quantity of network buffers or processor speed. Tweaking the task priorities might help increasing the throughput out the network driver.

• Few transitory errors. See the section on transitory errors on for more information.
• No retransmission. See the section on retransmission on for more details.
• No buffer leaks. See section “Buffer leaks” for more details.
• Logging performance results (with the target directly connected, and networked).