DRSTP: A Simple Technique for Preventing Count-to-Infinity in RSTP Controlled Switched Ethernet Networks

Ethernet is a dominant local area network (LAN) technology from last threedecades. Today most LANs are switched Ethernet networks. Spanning treeprotocol is a vital protocol for smooth operation of switched Ethernet networks.However the current standard of spanning tree protocol for Ethernet – commonlyknown as Rapid Spanning Tree Protocol or in short RSTP – is highly susceptibleto classical count-to-infinity problem. This problem adversely effects the networkconvergence time, depending upon how long count-to-infinity situation persists inthe network, and thus leads to network congestion and packet loss. In the worstcase, even forwarding loops may be induced that further enhances the networkcongestion. Thus, the dependability of RSTP controlled Ethernet networks arehighly questionable due to its vulnerability against the count-to-infinity problem.This paper first discusses the count-to-infinity problem in spanning tree controlledEthernet networks, in general and in RSTP controlled Ethernet networks, inparticular. Then this paper proposes a simple solution to overwhelm this problemefficiently.