User's Manual

Key Concepts 683
being much slower to respond than local devices. This is normal
behavior in a multi-site network. However, this delay may result in
3Com Network Director incorrectly reporting these devices as having
slow response times.
■ If the additional latency caused by WAN links is too high or if the WAN
links are unreliable then 3Com Network Director may conclude that
some remote devices are not responding at all. This will affect not
only the monitoring of these devices but will also prevent 3Com
Network Director from performing operations such as Network
Discovery, Backup, Restore, and Agent Update on these devices.
■ Active monitoring of a remote site causes 3Com Network Director to
generate additional management traffic to the devices at that site.
This increases the utilization of the WAN links between the local and
remote site. This increased utilization may increase the latency of the
WAN links and, if the increase causes the WAN links to become
oversubscribed, may result in the routers at either end of these links
discarding packets that are destined for the links.
See “
Monitoring Techniques” on page 276 for more details of active
monitoring.
3Com Network Director provides the following features to address these
issues:
■ Configurable timeouts
■ Configurable retries
■ Configurable poll rates for active monitoring
■ Configurable monitoring modes
■ Configurable discovery options
■ Configurable monitor thresholds
More details of each of these features are provided below.
In addition, if you manage your WAN routers directly, 3Com Network
Director will discover the WAN links in your network and add them to the
map, allowing you to monitor the usage of your WAN.
Configurable Timeouts
3Com Network Director communicates with devices by sending requests
and waiting for responses. If a request or response packet is dropped