MLT between ERS 5530 switch and an ERS 8600 switch
Multi-link trunking (MLT) is a link aggregation (IEEE 802.3ad) port trunking technology developed at Nortel in 1999. It allows grouping several physical Ethernet links into one logical Ethernet link to provide fault-tolerance and high-speed links between routers, switches, and servers. US patent 6731599, Van Hunter, Joseph Regan, Alfred Nothaft, Akhil Duggal; Regan, Joseph & Nothaft, Alfred et al., "Automatic Load Sharing-Trunking", issued 2004-05-04, assigned to Nortel Networks Limited and Avaya Holdings Limited
Using this technology allows or enables the use of several links (from 2 up to 8) and combined them to create increased bandwidth and several fail-over paths. This produces server to switch or switch to switch connections that are up to 8 times faster. In the past redundant links were unused due to Spanning Tree’s loop protection.
Fault-tolerant design is an important aspect of Multi-Link Trunking technology. Should any one or more than one link fail, the MLT technology will automatically redistribute traffic across the remaining links. This automatic redistribution is accomplished in less than half a second (typically less than 100 millisecond) 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. Combining MLT technology with Distributed Split Multi-Link Trunking (DSMLT), Split multi-link trunking (SMLT), and R-SMLT technologies create networks that support the most critical applications.
A general limitation of standard MLT is that all the physical ports in the link aggregation group must reside on the same switch. SMLT, DSMLT and R-SMLT technologies removes this limitation by allowing the physical ports to be split between two switches.