Multiplex communications – Fault recovery – Bypass an inoperative switch or inoperative element of a...
Patent
1997-11-17
1999-11-09
Nguyen, Chau
Multiplex communications
Fault recovery
Bypass an inoperative switch or inoperative element of a...
370402, 370220, H04J 116, H04J 314
Patent
active
059827459
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of implementing redundancy in LAN bridging/switching elements.
Redundancy is implemented in LAN bridging/switching elements in case of equipment failure. Implementing such redundancy is complicated because both elements must be constantly kept informed of network status changes. Furthermore, some switching techniques (e.g. LAN bridges) must be employed to monitor the data to decide on network topology.
The problem is that two independent switching/bridging elements that are configured to be redundant have to communicate this information to each other. If the data traffic has to be communicated to the inactive element in the redundant pair, then a large bandwidth pipe (typically a backplane or secondary high speed bus) must interconnect the two elements.
Alternatively, the newly active element must re-learn the new topology or network status by either asking another network element or by monitoring the data/protocols. This technique suffers from the disadvantage that there is a fairly large delay (incurred by this re-learning process) before traffic can resume as normal.
According to the present invention there is provided a method implementing redundancy in LAN bridging/switching elements wherein LAN traffic is sent to active and inactive elements using a multicast addressing technique.
The invention enables LAN to WAN Redundancy to be implemented using Multicast addressing, LAN protocol snooping, and a WAN wiring Hub.
LAN traffic destined for a traffic bridging element that is configured for redundancy is sent to both the active and inactive elements using multicast addresses.
In this specification, the term 'active' element refers to a switching element that is actively switching/bridging the traffic. 'Inactive' element refers to the LAN element that is passively listening/snooping the traffic, i.e. not switching the traffic. Data traffic is dropped by the inactive element.
The active element receiving the traffic can switch/bridge the traffic. The inactive element monitors the traffic and/or any protocols but does not switch the data. The appropriate control or status protocols are snooped (e.g. LAN bridges may snoop spanning tree protocols) in an attempt to remain in step with the status of the network. If activity switches to the 'inactive' (newly active) element, then the newly active element can assume immediate control without having to 'relearn' or renegotiate network status. The result is a reduction in lost data during activity switches.
The invention also provides a system for transferring data traffic between a frame relay network and an ATM network, comprising a pair of frame relay to ATM (FRATM) bridges, each said FRATM bridge being capable of transferring traffic between frame relay and ATM networks, and said FRATM bridges being capable of alternately being in an inactive standby mode and an active mode, the FRATM bridge in the active mode processing the data traffic for transfer between said networks, and the FRATM bridge in the standby mode merely snooping the data traffic to remain current as to network status; a frame relay engine for sending frame relay traffic to said FRATM bridges in both the inactive and active modes using multicast addressing over a LAN; a wiring hub for connecting the FRATM bridges over a common link to an ATM network; and means for switching said FRATM bridges between the inactive and active modes, whereby the FRATM bridge previously in the inactive mode assumes the processing of the data traffic from the FRATM bridge that was previously in the active mode.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:-
FIG. 1 is a block diagram of a typical system employing a FRATM bridge; and
FIG. 2 is a block diagram of a system implementing redundancy in accordance with the invention.
Referring to FIG. 1, a Frame relay terminal 10 communicates with a Newbridge Networks Corporation Fastbus.TM. 12 through a frame relay engine 11. The Fastbus 12 is conne
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Arcand Merrill
Brazeau Alain
Wirth Brian
Wolff Mark
Worthington Phil
Newbridge Networks Corporation
Nguyen Chau
Sam Phirin
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