Spanning Tree Protocol

Abstract: A protocol and algorithm are given in which bridges in an extended Local Area Network of arbitrary topology compute, in a distributed fashion, an acyclic spanning subset of the networkThe algorithm converges in time proportional to the diameter of the extended LAN, and requires a very small amount of memory per bridge, and communications bandwidth per LAN, independent of the total number of bridges or the total number of links in the networkAlgorhymeI think that I shall never see A graph more lovely than a treeA tree whose crucial property Is loop-free connectivityA tree which must be sure to span So packets can reach every LANFirst the Root must be selected By ID it is electedLeast cost paths from Root are traced In the tree these paths are placedA mesh is made by folks like me Then bridges find a spanning tree

Abstract: Radia Perlman's Interconnections is recognized as a leading text on networking theory and practice. It provides authoritative and comprehensive information on general networking concepts, routing algorithms and protocols, addressing, and the mechanics of bridges, routers, switches, and hubs. This Second Edition is expanded and updated to cover the newest developments in the field, including advances in switching and bridge technology, VLANs, Fast Ethernet, DHCP, ATM, and IPv6. Additional new topics include IPX, AppleTalk, and DECnet. You will gain a deeper understanding of the range of solutions possible and find valuable information on protocols for which documentation is not readily available elsewhere.Written by the inventor of many of the algorithms that make switching and routing robust and efficient, Interconnections, Second Edition offers an expert's insight into how and why networks operate as they do. Perlman describes all of the major networking algorithms and protocols in use today in clear and concise terms, while exploring the engineering trade-offs that the different approaches represent.The book contains extensive coverage of such topics as: The spanning tree algorithm The differences between bridges, routers, and switches Virtual LANs (VLANs) and Fast Ethernet Addressing and packet formats for IP, IPv6, IPX, CLNP, AppleTalk, and DECnet Autoconfiguration of addresses; strategies in various protocol suites Routing protocols, including RIP, IS-IS, OSPF, PNNI, NLSP, and BGP Layer 3 multicast protocols, including IGMP, DVMRP, MOSPF, CBT, PIM, BGMP, Simple Multicast, and Express Sabotage-proof routing Protocol design folklore 0201634481B04062001

Abstract: A method for operating a computer network includes: a become_root_primary command is issued to a first router to set an ID so that a spanning tree protocol (STP) selects the first router as a primary root router; a become_root_secondary command is issued to a second router to set an ID so that STP selects the second router as a secondary root router; transitioning, in response to failure of the first router, the second router to become the root router. An enable_uplinkfast command is issued to a router, and the router selects a backup designated port for a designated port, and selects a backup root port for a root port. Ports transmit BPDU messages as heartbeat messages, and a failure to detect the BPDU messages results in a backup port assuming the role of a port not detecting the BPDU messages.

Abstract: A shared spanning tree protocol (SSTP) creates a plurality of spanning trees (i.e., loop-free paths) which are shared among one or more virtual local area network (VLAN) designations for data transmission within a computer network. Each shared spanning tree includes and is defined by a primary VLAN and may be associated with one or more secondary VLANs. In order to associate VLAN designation(s) with a single shared spanning tree, network devices exchange novel shared spanning tree protocol data units (SST-PDUs). Each SST-PDU corresponds to a given primary VLAN and preferably includes one or more fields which list the secondary VLAN designations associated with the given primary VLAN. The association of VLAN designations to shared spanning trees, moreover, preferably depends on which path traffic is to follow as well as the anticipated load characteristics of the various VLANs. The association of VLAN designations to shared spanning trees thus provides a degree of load balancing within the network. Data messages tagged with a particular VLAN designation are then distributed by the devices only along the shared spanning tree to which that VLAN has been associated by SSTP.