Product and Software: This article applies to Aruba Controllers and Aruba Access Points running Arubas OS.
Controller and Access Points exchange GRE tunnel heartbeats every second to maintain the tunnel that carries user traffic. If these heartbearts get dropped or delayed consecutively then the AP would rebootstrap causing network unreachability for the wireless clients.
To avoid delays and prioritize these GRE heartbeats, we make use of the "Hearbeat DSCP" knob in ap system profile. Each heartbeat sent bi-directinal would be marked with a DSCP value which is then given appropriate importance by the network infrastructure in path.
We use this option in scenario's, where the APs or remote APs are located across low-speed (less than 1 Mb/s capacity) or high-latency (greater than 100 ms) links.With low-speed links, if heartbeat or keepalive packets are not received between the AP and controller during the defined interval, APs may reboot, which causes clients to re-associate. We can adjust the bootstrap threshold and prioritize AP heartbeats to optimize these types of links.
Below screenshots shows GUI and CLI configuration:
Below are the screenshots from Wireshark that shows the captured GRE heartbeats with and without DSCP priority:
NOTE: With DSCP tag, GRE heartbeats will be prioritized bi-directionally.
Without DSCP Priority:
With DSCP Priority
I have re-inserted the image "heartbeat_8"