Provider Link State Bridging (PLSB) is a technology developed by Nortel that evolved from Provider Backbone Bridges (PBB) specified in 802.1ah and Ethernet OAM - Operation, Administration, and Maintenance - specified in IEEE 802.1ag. As can be seen from the name Provider Link State Bridging, PLSB uses a Link State Protocol. Each dedicated VLAN of the backbone, B-VLAN, works with Link State Advertisements (LSA) and the Intermediate System to Intermediate System
Protocol (IS-IS) to discover the network structure and exchange state information.The PLSB nodes inform each other about the immediate neighboring nodes and which nodes are connected to each other and how. Intermediate System to Intermediate System Protocol (IS-IS), standardized by the International Standards Organization (ISO), is best suited for this purpose because of its flexibility and supports a wide variety of network protocols. In PLSB bridging, Intermediate System to Intermediate System (IS-IS) is used to exchange Layer 2 information, namely backbone MAC addresses (B-MAC) and I-Component Service
PLSB applies the SPF algorithm, Shortest Path First (SPF), and stores the calculated signal paths in the routing tables of the PLSB nodes. As a result, each individual node has its own view of the shortest transmission paths.