3com Corporation

Digital Equipment Corporation

3 Com Corporation

3com Corportion

Onfiber Communications, Inc.

Michael J Seaman

Stewart F Bryant

Neal Andrew Crook

Nagaraj Arunkumar

Tracy D Mallory

Vipin Kumar Jain

Mark S Isfeld

Bruce W Mitchell

Steven Paul Russell

John H Hart

Niles E Strohl

Jeffrey J Krause

John Rigby

Andrew J Walton

Una M Quinlan

John M Lenthall

Vincent G Gavin

Bipin Mistry

Fearghal Morgan

Joseph O'Callaghan

James Scott Hiscock

Chandrasekharan Nilakantan

Joris Johannes Maria Wils

Edward A Heiner, Jr

Ly Loi

Pyda Srisuresh

G Stodel Friedman

David L Brash

John Joseph Harrison, Jr

Helen C McGreal

Christopher R Szmidt

Mechanisms for use on designated ports in spanning tree protocol entities allow such ports to transition to a forwarding state on the basis of actual communication delays between neighboring bridges, rather than upon expiration of forwarding delay timers. The logic that manages transition of states in the spanning tree protocol entity identifies ports which are changing to a designated port role, and issues a message on such ports informing the downstream port that the issuing port is able to assume a forwarding state. The logic begins the standard delay timer for entry to the listening state and then the learning state, prior to assuming the forwarding state. However, when a reply from the downstream port is received, then the issuing port reacts by changing immediately to the forwarding state without continuing to await expiration of the delay timer and without traversing transitional listening and learning states. A downstream port which receives a message from an upstream port indicating that it is able to assume a forwarding state, reacts by ensuring that no loop will be formed by the change in state of the upstream port. In one embodiment, the downstream port changes the state of designated ports on the protocol entity which were recently root ports to a blocking state, and then issues messages downstream indicating that such designated ports are ready to resume the forwarding state. The designated ports on the downstream protocol entity await a reply from ports further downstream. In this way, loops are blocked step-by-step through the network, as the topology of the tree settles.

Spanning tree with protocol for bypassing port state transition timers

Modifications to the spanning tree algorithm allow bad news to propagate quickly by providing that protocol entities on bridges process inferior information sent by the designated bridge for each LAN. In addition, bridges use per port hello timers to stimulate information propagation, setting it to suit local link characteristics. No changes to the format of bridge protocol data units (BPDUs) as specified in the IEEE Standard 802.1D are required, and the algorithm for computing the topology of the network remains unchanged. Techniques have been adopted for expiring information and recomputing the spanning tree upon detection of link failure, upon receipt of a message having a message age greater than its accompanying maximum age, or if the port hello time algorithm detects a loss of link. Rules for propagating information are provided allowing rapid propagation of changes. Finally, techniques for burning out information in a configuration message are adopted.

Spanning tree with rapid propagation of topology changes

A method for configuring a network, and a network configured according to such method, are provide in which a communication links laid out in a ring in a metropolitan area are partitioned into link segments, and managed according to a spanning tree protocol. The switches are configured to establish unique, mesh or tree type network configurations suitable for application to communication media arranged to support ring-based protocols. The method is used for connecting communication links arranged in a plurality of rings, which traverse a plurality of collocation sites in a metropolitan area. The method comprises configuring switches in the plurality of collocation sites to partition rings in the plurality of rings into a plurality of link segments providing point to point paths between switches at collocation sites in the plurality of collocation sites. The switches and link segments are managed according to a spanning tree protocol. In one embodiment of the invention, the configuring of switches includes allocating a first set of the link segments as a first ring and a second set of the link segments as a second ring, breaking the first and second rings by blocking transmission on a link segment in the first ring between the first pair of collocation sites, and by blocking transmission on a link segment in the second ring between a second pair of collocation sites. In addition, the method includes cross-connection the first and second rings by a communication link.

Broadband tree-configured ring for metropolitan area networks

Management of forwarding databases in the case of link failures on bridges according to the all improved spanning tree, limits the propagation of notifications of topology change to only those parts of the network which are affected by the link failures, and trigger partial flushing as opposed to complete forwarding database flushing of learned MAC addresses to relearn the sets of addresses associated with ports affected by the change in topology. When a bridge moves its root port to a new port, the bridge can move the addresses learned through the original root port to the new root port without any relearning. The sets of addresses associated with the designated ports on upstream bridges from the old root port, are subject to flushing. Also when the bridge attaches to the new branch, it triggers a message to the root instructing all bridges in the new path to the root to flush addresses learned on their root ports.

Spanning tree with rapid forwarding database updates

An improvement to the spanning tree protocol provides for identifying a port on the bridge in the alternate port role which qualifies as a next best root port. Upon detection of a failure at the root port, or other event causing a change in the root port to a blocking state, the next best root port transitions to the root port role, and forwarding state immediately without traversing the listening and learning states of the standard protocol. Also, in networks in which there is a possibility of shared media links between bridges, ports that have the alternate port role, and connect to a LAN which is also connected through a designated port on the same bridge are identified as a backup. The algorithm prevents such backup ports from transitioning to the forwarding state before the designated port connected to the same LAN segment transitions to a blocking state.

High availability spanning tree with rapid reconfiguration

A packet based high speed mesh forms a trunk cluster. The trunk cluster is constructed with a set of loosely coupled switches, a configuration protocol, trunked network interfaces, and optionally a reachablilty protocol. The trunk cluster provides a Logical LAN service. Each switch in the trunk cluster provides a single &ldquo;shared LAN&rdquo; by interconnecting two or more links. The edge devices attached to the links run a trunk configuration protocol. These attached edge devices view the trunked ports as if trunked ports are connected to a shared LAN with multiple other attached devices.

Scalable logical LAN

A communication technique for high volume connectionless-protocol, backbone communication links in distributed processing systems provides for control of latency and reliability of messages transmitted. The system provides for transmit list and receive list processes in the processors on the link. On the transmit side, a high priority command list and a normal priority command list are provided. In the message passing process, the command transmit function transmits commands across the backplane according to a queue priority rule that allows for control of transmit latency. Messages that require low latency are written into the high priority transmit list, while a majority of messages are written into the high throughput or normal priority transmit list. A receive filtering process in the receiving processor includes dispatch logic which dispatches messages either to a high priority receive list or a normal priority receive list. The filtering function also acts to drop messages received according to the amount of available buffer space in the receiving processor, as measured against watermarks based on reliability tags in message headers. The messages received are routed to either the high priority receive list or a normal priority receive list based on another control bit in the message headers. The receiving processor processes the messages in the receive queues according to a priority rule that allows for control of the latency between receipt of a message, and actual processing of the message by the receiving processor.

High throughput message passing process using latency and reliability

A high performance scalable networking bridge/router system is based on a backbone communication medium and message passing process which interconnects a plurality of input/output modules. The input/output modules vary in complexity from a simple network interface device having no switching or routing resources on board, to a fully functional bridge/router system. Also, in between these two extremes input/output modules which support distributed protocol processing are supported. A central internetworking engine includes a shared memory resource coupled to the backbone. The architecture includes a physical layer communication system for transferring control messages and data packets across the backbone, a logical layer interprocessor messaging system which operates over the physical layer across the backbone for communication between intelligent input/out modules, and between such modules in the central internetworking engine, and distributed protocol modules which are supported on intelligent input/output modules, and communicate using the logical interprocessor messaging system with the central internetworking resources.

Bridge/router architecture for high performance scalable networking

Resources for computing an active network topology in a system having a plurality of ports coupled to respective local area networks include a protocol entity coupled to the plurality of ports which communicates with protocol entities in other systems on the networks to establish the active network topology. Port state logic, coupled with the protocol entity and the plurality of ports establishes active network states for the plurality of ports. The active network states include a first network state for forwarding data and a second network state for blocking data, wherein a transition from a first network state to a second network state is executed after receiving information from the protocol entity indicating a change to the second network state. A transition from the second network state back to the first network state is executed upon expiry of a waiting interval after receiving information from the protocol entity indicating a change to the first network state, unless information indicating a change to the first network state is received within a forgetting interval after a change from the first network state to the second network state. If the information indicating such change is received prior to expiry of the forgetting interval, then the transition is executed immediately.

Active topology maintenance in reconfiguring bridged local area networks

In an apparatus in a computer network, message filtering proceeds by generating respective class specifiers from a received message, using the message source field, message destination field, and type of message field. The class specifiers are used for generating a class specification, and a domain class is generated from the class specification. A domain list is generated to provide a list of ports to which a message directed to the domain class is to be forwarded. The message is forwarded to the ports listed in the domain list. The apparatus may be a bridge, router, etc.

Apparatus for message filtering in a network using domain class

A data transfer device for coupling a processor to a system bus. The data transfer device includes data packers and unpackers for converting between data blocks of a first size and data blocks of a second size, e.g. between bytes or words and longwords. The data transfer device also includes an internal buffer memory system for storing the data being transferred. The processor and system bus are selectively coupled, each one at a time, via a direct data path, to the internal buffer memory system permitting both the processor and the system bus to independently read and write data, each at their normal data transfer rate.

Data transfer system for buffering and selectively manipulating the size

A system uses a message passing paradigm for transferring large amounts of input/output data among a plurality of processors, such as a network intermediate system or router. A bus interconnects the plurality of processors with a plurality of bus interface devices. The bus interface device which originates a transfer includes a command list storing lists of commands which characterize transfers of data messages from local memory across the bus and a packing buffer which buffers the data subject of the command being executed between local memory and the bus. A bus interface device which receives a transfer includes a free buffer list storing pointers to free buffers in local memory into which the data may be loaded from the bus, and a receive list storing pointers to buffers in local memory loaded with data from the bus. The command list includes a first high priority command list and a second lower priority command list for managing latency of the higher priority commands in the software of the processor. The bus interface which receives the transfer includes control logic which manages data transfer into and out of an inbound buffer, including receiving burst transfers of message transfer cells from the bus, loading free buffers in local memory from the inbound buffer with message transtar cells, and updating the receive list. The receive list includes a first higher priority receive list and a second lower priority receive list for reliability management, and logic which monitors the free list so that lower priority messages may be dropped to prevent overflow of free buffer resources.

Network intermediate system with message passing architecture

Growing community of inventors

San Jose, CA, United States of America

Michael J Seaman