the IST and the total forwarding capacity of the switches in the cluster is also aggregated. The communication between peer switches across the IST allows both unicast and multicast routing information to be exchanged allowing protocols such as Open Shortest Path First (OSPF) and Protocol Independent Multicast-Sparse Mode (PIM-SM) to operate correctly. Failure scenarios The use of SMLT not only allows traffic to be load-balanced across all the links in an aggregation group but also allows traffic to be redistributed very quickly in the event of link or switch failure. In general the failure of any one component results in a traffic disruption lasting less than half a second (normal less than 100 millisecond) making SMLT appropriate in environments running time- and loss-sensitive applications such as voice and video. In a network using SMLT, it is often no longer necessary to run a spanning tree protocol of any kind since there are no logical bridging loops introduced by the presence of the IST. This eliminates the need for spanning tree reconvergence or root-bridge failovers in failure scenarios which causes interruptions in network traffic longer than time-sensitive applications are able to cater for. Product support SMLT is supported within the following Avaya Ethernet Routing Switch (ERS) and Virtual Services Platform (VSP) Product Families: ERS 1600, ERS 5500, ERS 5600, ERS 7000, ERS 8300, ERS 8800, ERS 8600, MERS 8600, VSP 9000 SMLT is fully interoperable with devices supporting standard MLT (IEEE 802.3ad static mode). R-SMLT Routed-SMLT (R-SMLT) is a computer networking protocol developed at Nortel as an enhancement to split multi-link trunking (SMLT) enabling the exchange of Layer 3 information between peer nodes in a switch cluster for resiliency and simplicity for both L3 and L2. In many cases, core network convergence time after a failure is dependent on the length of time a routing protocol requires to successfully converge (change or re-route traffic around the fault). Depending on the specific routing protocol, this convergence time can cause network interruptions ranging from seconds to minutes. The R-SMLT protocol works with SMLT and distributed Split Multi-Link Trunking (DSMLT) technologies to provide sub-second failover (normally less than 100 milliseconds) so no outage is noticed by end users. This high speed recovery is required by many critical networks where outages can cause loss of life or very large monetary losses in critical networks. RSMLT routing topologies providing an active-active router concept to core SMLT