Enabling High Performance Data Transfers brought by: David Acker

http://www.psc.edu/networking/projects/tcptune/

Audience:

System administrators and privileged users.

Type of Document:

Notes, tutorial.

Summary:

    The TCP/IP protocol was not designed to support high transmit rates as today's. Extensions have been added to TCP/IP in order to support high performance options, however, they have to be explicitly turned on by system administrators. For example, the amount of memory or buffer space that a connection uses can be limited the operating system. Moreover, the socket buffer size can be relatively small to the bandwidth and drastically slow it down. The system admin should change the socket's buffer in order to maximize the usage of the bandwidth. Window sizes also play an important role in a TCP transmission. RFC1323 allows TCP to support WSCALEs that are larger than the maximum window size used by the original TCP (64K). By enabling the SACK (Selective Acknowledgment) option, the TCP receiver will inform the sender which data is missing and needs to be retransmitted. By enabling all these high performance options, a system admin can maximize the usage of the bandwidth.

Conclusion:

Before using any system, the system administrator should be aware of all the underlying protocols and hardware in order to maximize the performance of his system.