IEEE Std 1910.1-2020 pdf download – IEEE Standard for Meshed Tree Bridging with Loop‐Free Forwarding.
5. Mesh tree algorithm and the protocol The MTA allows construction of logically meshed subtrees from a single root bridge in a distributed manner using local information shared among neighbor MTBs. The MTA is first described using a flowchart in Figure 1. A root is preselected or designated. Preselection or designation does not impact the MTBP operation (see 7.2.4). Annex A provides formal definitions for meshed trees. In MTBP, for the construction and maintenance of multiple subtrees from a single root in a bridged network, virtual identifiers (VIDs) are assigned to the communicating bridges. A single communicating non-root bridge can acquire multiple VIDs. The VID is henceforth called meshed tree VID (MT_VID). Each MT_VID derived in MTBP defines a non-looping path from the communicating bridge to the root bridge. This is true for all communicating bridges except the root bridge. The root bridge has a single MT_VID that shall be assigned to it, when it is predesignated to be the root bridge. NOTE—For an implementation of MTBP, a root bridge is designated and assigned a VID. 6 6. Meshed tree algorithm The MTA supports construction of multiple subtrees from a single root. The flow chart for the MTA using a connected graph is given in Figure 1. In this graph, a vertex is defined to be the root. The meshed tree construction starts with all vertices checking if they have the root status or not. The vertex that has this status sends out path invitations (PI) to its neighboring vertices. If a neighbor accepts the invitation, the root notes this neighbor as part of its meshed tree. Vertices that do not have the root status listen for PIs. When they receive a PI, they first perform a loop-check, and if the PI does not result in loop formation with already accepted PIs, the vertex accepts the new PI. It then stores all PIs in a list and sorts them in order of hop count from the root. The extent of meshing among the subtrees can be restricted to K max , i.e., a vertex can reside in a maximum of K max subtrees from a root.