HP Network Direr Software Products manual Using 3COM Network Director on a MULTI-SITE Network

702CHAPTER 17: USING 3COM NETWORK DIRECTOR ON A MULTI-SITE NETWORK

For example, by default 3Com Network Director will retry a failed IP ping request an additional 2 times, and give each IP ping request a 2 second timeout period. This means that, during the IP Ping stage of a Network Discovery, it will take 3Com Network Director 6 seconds before it concludes that an IP address is not going to respond. If you increase the number of retries to 4 and the timeout period to 6 seconds then this will increase the length of time before 3Com Network Director concludes that an IP address is not going to respond to 30 seconds, five times longer than before. If a large number of the IP addresses on the subnet(s) being discovered are not responding then this could slow the Network Discovery down by several minutes.

As a result, it is important that the numbers of retries and timeout periods that you configure for the different sites and devices on your network accurately reflect the normal responsiveness and reliability of your network.

One method of determining appropriate numbers of retries and timeout periods is to take samples of the responsiveness and reliability of the different sites on your network over time and under different network conditions and then use these to determine appropriate values.

For example, the responsiveness of a site to IP ping requests may be measured by sending IP ping requests to a selection of important devices located at that site at regular intervals, such as every 5 minutes, over some period, such as a working week, and recording the results. Any samples where the remote site failed to respond at all can be ignored, as these likely indicate periods when either the device that the request was sent to or the entire remote site was uncontactable. The results can then be used as follows:

The maximum number of retries that were needed to receive a response to an IP ping request during the sample period provides an indication of the reliability of the connectivity to that site. The number of retries for IP ping requests should be set to at least this maximum number of retries.

Note that if your sample period did not include any samples when the connectivity was particularly unreliable then it may be advisable to add an additional retry on top of your measured maximum number of retries to allow for such unreliability.

The longest response time to an IP ping request provides an indication of the latency of the connectivity to that site. Round this response time up to the nearest 500 ms and set the timeout period for IP ping requests to