Research And Improvement Of Count-to-infinity In Rapid Spanning Tree

As the heterogeneity of network equipment and defects in design of network protocol, research of network management and improvement of protocol algorithm has much theoretical and practical significance. Spanning Tree Protocol is one of the basic protocols for the network equipment in OSI Layer 2.The physical topology connected by the bridges allows loops to provide alternate paths for varied incidents, making the network strong and robust.When broadcasting in Layer 2,Data frames continues to be forwarded in the loops and becomes the broadcast storm which disables the network.Spanning Tree Protocol, STP controls the state of the ports in the bridge providing the logical tree with no loops for the physical network.Data frames can go along the tree which sovles the problem of broadcast storm.STP has a defect that it takes long time to constring. Rapid Spanning Tree Protocol, RSTP, defines new roles for the ports.Designated Ports can transitions to forwarding after the handshake with its children bridges in the point-to-point link.Edge Ports connected with the hosts can transitions to forwarding immediately. RSTP just resolves the problem of long constringency in STP.But the contest race between the RSTP state machines leads to a tempory loop after the count-to-infinity problem in tens of seconds during which congestions can be sharply increased and data frams are forwarded incorrectly.My main work is as follows:1. Reserach the basic theory of RSTP .I focus on 3 citical state machines, Port Role Selection machine, Port Role Transition machine and Port State Trantion machine,and analyze the detailed conditions with which it transitions from one state to another.2. Introduce the count-to-infinity problem in RSTP. Analyze the conditions under which it presents and how it leads to a temporary loop.Then propose a solution for improvement, RSTP with Sequences, to relove the problem.3. Design and implement RSTP with Sequences base on RSTP module and test.