Configuring a network topology involves specifying uplinks. An uplink is the last network segment connecting the local site to a network. At a high level, you can define multiple uplinks to a given network. The appliance monitors the state of the uplink and, based on this, selects the appropriate uplink for a packet. Selecting appropriate uplinks for packets provides more control over network link use.

Remote uplinks are also important for QoS because they define the available bandwidth for remote sites. RiOS uses the specified bandwidth to compute the end-to-end bottleneck bandwidth for QoS.

You can define an uplink based on an egress interface and, optionally, the next-hop gateway IP address. You can specify different DSCP marks per uplink for a given flow, allowing an upstream router to steer packets based on the observed marking.

To monitor uplink availability; you configure the latency of the uplink (timeout) and the loss observed (threshold). Path selection uses ICMP pings to monitor the uplink state dynamically, on a regular schedule (the default is 2 seconds). If the ping responses do not make it back within the probe timeout period, the probe is considered lost. If the system loses the number of packets defined by the probe threshold, it considers the uplink to be down and triggers an alarm, indicating that the uplink is unavailable.

If one uplink fails, the appliance directs traffic through another available uplink. When the original uplink comes back up, the appliance redirects the traffic back to it.

You can configure up to 1024 direct uplinks.