Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-01-28
2001-02-27
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S254000, C370S406000
Reexamination Certificate
active
06195351
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to network systems and more particularly to techniques and device models to provide high availability interface systems including link and switch redundancy.
BACKGROUND OF THE INVENTION
Traditionally spanning tree (a spanning tree protocol) has been use to provide both Layer
1
and
2
redundancy, in switch networks, by configuring alternate paths. When a link or switch element fails, a backup link is activated. The spanning tree algorithm defines the active and backup links in the topology. Spanning tree is designed to control the many switches of the topology and has a slow (in the tens of seconds) reconfiguration time.
Spanning tree has a significant disadvantage as to the reconfiguration time. As network systems become more complex and handle additional traffic, the reconfiguration time becomes increasingly problematic.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the invention to provide layer one and layer two redundancy and switch network systems which avoid the use of Spanning Tree by the use of multiple switches forming a single logical switch that can participate in topology control protocols (e.g. Spanning Tree and GARP) for each VLAN (virtual LAN), unicast and multicast and can share MAC address learning information. The invention provides two or more switches which combine to provide a single packet forwarding device.
According to the invention a Logical Switch Set (LSS) is provided comprising two or more switches that act as a single packet forwarding device with specific connection rules. The LSS may be used as either a redundant switch set (RSS) or as a Load Sharing Switch Set (LSSS). The maximum throughput of the LSSS increases with each additional switch. A LSSS can only interconnect with the other devices via trunked links that contain at least one physical connection to each switch (A through N). This prevents any single link attachments to the LSSS. This also implies that if a link is lost, leaving no remaining links to that switch, then LSSS can either chose to drop service to that station or stop using that switch for load sharing for all connected devices. Effectively removing that switch from LSSS.
The LSS implements a single logical device which is comprised of two or more separate switches. This logical device can operate as a simple packet forwarding device, a full function fully manageable switch, or any variation between these extremes. The simplest non filtering packet forwarding device need not share any state information between devices. A full function fully manageable switch model requires that state or parameter changes, acquired from the traffic streams a switch receives, be shared between the other switches. State and parameter changes can occur from learning MAC source addresses and processing management and control frames. Management and control frames destined for the logical device will be directed to one of the switches by the traffic steering algorithm of an attached device. Each switch in the LSS implements one or more of the physical links, within a trunked group, for each the ports of the logical device. Each switch must have a unified view of the logical switch and port parameters to properly forward traffic and to transmit management and control frames. This sharing of state information requires a communication path between switches in a LSS. This communication path may be a dedicated resource.
A LSS may be implemented either as a primary/backup pair (or group) or as a load sharing set. The primary/backup method uses one device to perform the traffic forwarding and management functions while the other device maintains up to date state information from the primary device, ready to take over if the primary device fails or is removed. The load sharing switch set method spreads the load of traffic forwarding and management across all the switches in the set.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.
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Friedman G. Stodel
Harrison, Jr. John Joseph
Heiner, Jr. Edward A.
Hiscock James Scott
Van Seters Stephen Luke
3Com Corporation
Chin Wellington
McGlew and Tuttle , P.C.
Nguyen Steven
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