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 SteelHead 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. Configuring a network topology requires defining uplinks.

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.

The uplink probing frequency can affect the scaling and performance of hybrid networks. Leveraging the SteelHead’s traffic awareness, you can accelerate probing to sites that are seeing traffic, while backing off probing for sites that aren’t seeing traffic. Uplinks are probed at the uplink Timeout default rate of 2 seconds only if there is traffic at the site or if there is path failover, otherwise probing is backed off using the Max Backoff Interval of 1800 seconds. You configure the Max Backoff Interval when you define a network. You can change the Max Backoff Interval to whatever value are best suited for your hybrid network.

If the probe responses don’t make it back within the probe time-out 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 SteelHead directs traffic through another available uplink. When the original uplink comes back up, the SteelHead redirects the traffic back to it.

Path selection uses only local uplinks. You can also create site connectivity templates, which consist of a set of one or more uplinks for use with multiple sites that share the same uplink structure, such as dual uplink sites or branch sites. When the site connectivity template is applied to a site, the uplinks defined in the template uplinks are cloned. For details about site templates, see About site connectivity templates.

For detailed information about defining tunneled uplinks, see the SteelHead User Guide.