XRoads Networks Multilink Outage Detection (MOD)

Multilink Outage Detection (MOD)

False outages and undiscovered outages are a major potential problem when implementing a network load balancer. Many network load balancers simply do not perform enough testing to know when an outage has actually occurred, or they may trigger an outage simply when a high latency event has occurred.

Deep Network Probing
To protect against these potential pitfalls the Edge appliance implements multi-level outage detection which performs various network tests in order to determine the true status of each link.

False Outages

Generally occur when a device is probing a network connection and due to some form of high latency, created either from normal high traffic usage or a potential hacking attempt, will cause the device to trigger an outage.

The problem with this is that it generally means that existing sessions are dropped (worst case) or delayed while the device turns down the "bad" link.

Undiscovered Outages

A potentially worst scenario is one in which the device does not perform enough testing, perhaps it only tests the local gateway connection, if the actual WAN link itself failed, or the local ISP was having problems with its connectivity to the Internet, the device would not see this problem and continue to forward traffic over the bad link.

How Does It Work

Using a patent-pending method for performing Deep Network Probing the Edge appliance not only tests the local connectivity, but continues to test out to the various points on the Internet to ensure that full connectivity is available.

When private networks are being balanced, the Edge appliance can be configured to only test the local and remote gateways thus ensuring full site-to-site connectivity.

Using multiple level testing the Edge appliance also ensures against temporary high-latency events from causing a link failure event. Only a sustained high latency event will trigger such action, thus preventing any session breakdowns from re-routing traffic.