M A G N U M 6 K S W I T C H E S , M N S - 6 K U S E R G U I D ES-Ring and LLL conceptsS-Ring is built upon networking software standards such as IEEE02.1d Spanning Tree Protocol (STP) or Rapid Spanning Tree ProtocolSTP) based on IEEE 802.1w. The purpose of S-Ring is to define twoorts which participate in the RSTP/STP tree structure in a ringtopology as opposed to a meshed topology. S-Ring running on the ringmanager switch leverages this capability to recover quickly from fault situations. Therecovery times for S-Ring based networks are within a few hundred milliseconds.Recovery time for STP devices is in tens of seconds (typically 30-50 seconds in mostnetworks) or sub second to a few seconds for RSTP networks. The biggestadvantage of S-Ring, besides the fast recovery time, is the defined ring topologywhich makes the network manageable. S-Ring can also be an overall lower costsolution as there are hubs as well as switches which can be used in the ring.8(RpjIn the Magnum 6K family of switches as well as in other unmanaged switches suchas the ESD42, a feature called Link-Loss-Learn™ (LLL) can be activated toimmediately flush its address buffer and relearn the MAC addresses that routepackets around the fault. This procedure, which is similar to switch initialization,occurs within milliseconds, resulting in fast ring recovery. An S-Ring implementationwatches for link-loss as well as for STP/RSTP BPDU packet failures and respondsto whichever occurs first. In most instances the link-loss will be detected faster thanthe two-second interval at which the BPDU packets are successfully passed aroundthe ring. Typical ring recovery times using S-Ring software and mP62 edge switcheswith the LLL feature enabled on the ring ports is less than 250 milliseconds, evenwith 50 or more Magnum 6K family of switches in a ring structure. Without LLLactivation, the Magnum 6K family of switches address buffer aging time (5 minutesdefault) could be the gating factor in ring recovery time. LLL is used on S-Ring andhelps speed up the ring recovery time.S-Ring operates from specifically defined port pairs that participate in a ring-topology. Multiple rings of different pairs on the same switch are also supported;however, intersecting rings or a “ring of rings” or “overlapping rings” is notsupported in the current version. While S-Ring builds upon the foundation of RSTPor STP, S-Ring offers an additional topology option to network architects. The twoends of a ring must be connected to two ports in a Magnum 6K Switch that isenabled with the S-Ring software. The end points of the ring provide an alternatepath to reach the switch that has failed. The in-out pairs of the ports to other devicesin the ring have to be enabled with LLL. Some items to be aware of with S-Ring areas follows:1. The S-Ring feature is a separately licensed module for the MNS-6K softwarepackage. This module must be enabled by means of a software key2. Only one switch is the “Ring Master”. That switch has S-Ring Softwareauthorized (enabled) for that device. Thus only one license key is needed perring (and not per switch)175
