Determining the Bandwidth-Delay Product

14.3 Determining the Bandwidth-Delay Product

Bandwidth-delay product is the product of network bandwidth and the round trip time of data going over the network. A simple way to determine the round trip time, is to use a command such as ping from one host to another and use the response times returned by ping.

For example, if a network has a bandwidth of 100 Mbps and a round trip time of 5ms, then the send and receive buffers should be at least (100*10ˆ6) * (5/10ˆ3) bits or approximately 62.5 Kilobytes.

The following equation shows the relationships between the units and factors involved:

100,000,000 bits   1 byte   5 seconds
---------------- x ------ x --------- = 62,500 bytes
 1 second          8 bits     1000

Setting the SEND_BUF_SIZE and RECV_BUF_SIZE parameters to at least the bandwidth-delay product insures that when large amounts of data are being sent that the network bandwidth will be optimally utilized.

Based on the preceding equation, the bandwidth-delay product of this network link is approximately 64 KB. If the largest message used to transfer redo data between a primary database and a standby database is 1 MB, then the value for the SEND_BUF_SIZE and RECV_BUF_SIZE parameters could be 1 MB. However, if the average message is less, then a setting of 64 KB should be sufficient to optimize use of the available bandwidth.

For most network protocols, ensure that the RECV_BUF_SIZE parameter at one end of the network connection, typically at the client, equals the value of the SEND_BUF_SIZE parameter at the other end, typically at the server.