How does EPSR SuperLoop Prevention work?

EPSR SuperLoop Prevention (EPSR-SLP) is an enhancement to the original EPSR.

EPSR-SLP prevents SuperLoops forming in the following way:

  1. A priority is assigned to each EPSR ring between 0 and 127, with 1 representing the lowest priority and 127 the highest. A priority of 0 (the default setting) applies the functionality of no SuperLoop prevention.
  2. It ensures that common segment Transit nodes send Link Down messages only to the Master of the highest priority ring.
  3. When a link in a common segment goes down, only the Master of the highest priority ring opens its Secondary port, because this is the Master node that will receive the Transit node’s Link Down message.


Ethernet is becoming the universal data transport medium in the world. With the diversification of the applications for which Ethernet data transport is used, the requirements on the performance of Ethernet grow. In particular, the application of Ethernet to the transport of real time video and voice communications has required that Ethernet provides extremely fast fault recovery mechanisms. The failover in the event of link or node failure needs to be so fast as to be barely perceptible to the human eye or ear.

Moreover, a highly fault-tolerant Ethernet network must also continue to provide the key advantages of Ethernet—cost-effectiveness, simplicity, flexibility.

Allied Telesis’ EPSR provides an effective solution to address this challenge. It monitors the ring’s domain and maintains operational functions, to detect faults and respond immediately to achieve ring recovery as quickly as 50ms. It enables network engineers to manage multiple data VLANs using a simple, reliable protocol. It is flexible, cost-effective, scalable, and greatly improves network resiliency. Allied Telesis’ EPSR ensures Ethernet ring networks can handle the stress of providing voice, video, and data services.