Multiplex communications – Pathfinding or routing – Through a circuit switch
Reexamination Certificate
1998-01-28
2001-02-27
Chin, Wellington (Department: 2731)
Multiplex communications
Pathfinding or routing
Through a circuit switch
C370S255000, C370S400000
Reexamination Certificate
active
06195349
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to network systems such as Local Area Network (LAN) systems and more particularly to techniques and device models to provide high availability interfaces, and systems.
It has been generally known in the network systems field how to provide redundant capabilities. Redundant packet forwarding devices are especially useful to handle the possibility of failed links and/or failed packet forwarding devices (e.g. switches, routers, bridges). However, the detection of network topology loops and the utilization of redundant paths is problematic, particularly in view of the time involved in detecting the path and rerouting traffic. Further, protocols which have been used are complicated to configure and manage.
Traditionally the 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. Further, spanning tree disables the redundant path. This negates the possibility of using redundant paths for increases in throughput.
FIELD OF THE INVENTION
The invention relates generally to network systems such as Local Area Network (LAN) systems and more particularly to techniques and device models to provide high availability interfaces, and systems.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the invention to provide network layer one and layer two redundancy in switch network systems which avoid the use of spanning tree by the use of multiple switches forming a trunk cluster switch which provides additional switch throughput for each additional switch provided in the switch cluster.
According to the invention a packet based high speed mesh is provided which is refereed to herein as a trunk cluster. The trunk cluster cooperates with edge devices to provide a scaleable logical LAN. The trunk cluster is constructed with a set of loosely coupled switches, a configuration protocol, trunked network interfaces, and optionally a reachablilty protocol.
Each switch in the trunk cluster provides a single “shared LAN” by interconnecting two or more links. The edge devices attached to the links run a trunk configuration protocol. These attached edge devices view each physical link within a trunked port as if the attached device is connected to a shared logical LAN with multiple other attached devices.
A logical LAN is designed to provide scaleability and resilience. The set of devices (and devices, switches etc.) that interconnect to a logical LAN, called edge devices, cooperate using configuration protocols and traffic steering methods required to connect to the logical LAN.
The trunk cluster is comprised of two or more trunk switches. A single logical LAN is provided by the edge devices splitting the traffic (directing traffic flow) across the links in a trunk port. Each trunk switch provides a separate path within the trunk cluster (multiple parallel paths are provided). The two or more separate paths between edge devices allow the logical LAN to increase bandwidth by adding more trunk switches and automatically decrease bandwidth in the event of a link failure and/or in the event of a trunk switch failure.
As each trunk switch only carries part of the traffic between edge devices, each trunk switch does not need to and must not participate in any topology control or discovery protocol. Spanning tree, TCMP (Trunk Cluster Management Protocol), IGMP (Internet Group Management Protocol), and GARP (Generic Attribute Registration Protocol) packets are flooded. Unicast MAC (Media Access Controller) source addresses are learned and used to intelligently forward/filter unicast packets to minimize flooding within the “shared LAN” and increase throughput. The maximum throughput of the trunk cluster increases with each additional trunk switch.
Each MAC device of an edge device transmits an hello signal to MAC devices of other edge devices. The hello signal includes a trunk or edge device ID identifying the respective edge device of the MAC device transmitting the hello signal. Each MAC device records the edge device ID's of said hello signals received from other edge devices. These recorded edge device ID's are formed into an hello list for each MAC device. The TCMP agent of an edge device forms a trunk list for each other edge device. Each trunk list for a particular other edge device includes MAC addresses of the present edge device which received the hello signals from the respective one of the other edge devices. For example, if edge device A had three MAC devices which received hello signals from edge device B, edge device A would have a trunk list for edge device B which contained those three MAC devices. When edge device A received traffic for edge device B, edge device A would divide the traffic among the three MAC devices in the trunk list for edge device B. This dividing of traffic received by edge device A for edge device B, is according to the standard trunking convention. In this way, trunking can be accomplished through a plurality of switches in a mesh instead of just over a plurality of links where all the links start and stop at the same nodes. Also the trunking of the present invention allows links to be active and increase data rates, where previously those links would have been inactive due a redundancy decision by a spanning tree algorithm.
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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patent: 5825772 (1998-10-01), Dobbins et al.
patent: 5949788 (1999-09-01), Friedman et al.
patent: 5959968 (1999-09-01), Chin et al.
patent: 5959989 (1999-09-01), Gleeson et al.
patent: 6016310 (2000-01-01), Muller et al.
patent: 6032194 (2000-02-01), Gai et al.
patent: 6035105 (2000-03-01), McCloghrie et al.
patent: 6041057 (2000-03-01), Stone
patent: 6049528 (2000-04-01), Hendel et al.
Friedman G. Stodel
Harrison, Jr. John Joseph
Heiner, Jr. Edward A.
Hiscock James Scott
Seaman Michael John
3Com Corporation
Chin Wellington
McGlew and Tuttle , P.C.
Nguyen Steven
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