Key Concepts 683being much slower to respond than local devices. This is normalbehavior in a multi-site network. However, this delay may result in3Com Network Director incorrectly reporting these devices as havingslow response times.■ If the additional latency caused by WAN links is too high or if the WANlinks are unreliable then 3Com Network Director may conclude thatsome remote devices are not responding at all. This will affect notonly the monitoring of these devices but will also prevent 3ComNetwork Director from performing operations such as NetworkDiscovery, Backup, Restore, and Agent Update on these devices.■ Active monitoring of a remote site causes 3Com Network Director togenerate additional management traffic to the devices at that site.This increases the utilization of the WAN links between the local andremote site. This increased utilization may increase the latency of theWAN links and, if the increase causes the WAN links to becomeoversubscribed, may result in the routers at either end of these linksdiscarding packets that are destined for the links.See “Monitoring Techniques” on page 276 for more details of activemonitoring.3Com Network Director provides the following features to address theseissues:■ Configurable timeouts■ Configurable retries■ Configurable poll rates for active monitoring■ Configurable monitoring modes■ Configurable discovery options■ Configurable monitor thresholdsMore details of each of these features are provided below.In addition, if you manage your WAN routers directly, 3Com NetworkDirector will discover the WAN links in your network and add them to themap, allowing you to monitor the usage of your WAN.Configurable Timeouts3Com Network Director communicates with devices by sending requestsand waiting for responses. If a request or response packet is dropped
