Multiplex communications – Fault recovery – Bypass an inoperative switch or inoperative element of a...
Reexamination Certificate
1998-04-29
2002-04-02
Ngo, Ricky (Department: 2664)
Multiplex communications
Fault recovery
Bypass an inoperative switch or inoperative element of a...
C370S228000, C370S419000
Reexamination Certificate
active
06366557
ABSTRACT:
COPYRIGHT NOTICE
Contained herein is material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction of the patent disclosure by any person as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all rights to the copyright whatsoever.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the field of computer networking devices. More particularly, the invention relates to a Gigabit media access controller (GMAC) having support for redundant physical links.
2. Background Information
With Local Area Network (LAN) switches now operating at data transfer rates of up to 1 Gigabit per second (Gbps), switch-over from a failed physical link to another physical link is of critical importance.
As used herein, the terms Ethernet, Fast Ethernet, and Gigabit Ethernet shall apply to Local Area Networks (LANs) employing Carrier Sense, Multiple Access with Collision Detection (CSMA/CD) as the medium access method, generally operating at a signaling rate of 10 Megabits per second (Mbps), 100 Mbps, and 1,000 Mbps, respectively over various media types and transmitting Ethernet formatted or Institute of Electrical and Electronic Engineers (IEEE) standard 802.3 formatted data packets.
In the prior art there are methods and systems which support redundancy of signals, however, the switch-over from the failed data stream to the redundant data stream in the prior methods and systems tend to have a long latency.
In one prior art switch system two media access controllers (MACs) are used to create a redundancy of signals between the switch and the respective source and/or destination port.
FIG. 1
illustrates a switch
150
that uses two MACs
160
&
165
to create redundant links between the switch
150
and at least one of input/output (I/O) devices
101
-
104
. One of the MACs
160
&
165
is the primary MAC and the other is the redundant (or backup) MAC. Both MACs
160
&
165
set up links to the desired source and/or destination port, here one of the I/O devices
101
-
104
. For the sake of an example, MAC
160
sets up a primary link to I/O device
102
and MAC
165
sets up the redundant link to the same I/O device
102
. While MAC
160
communicates with I/O device
102
along the primary link, the redundant link remains idle with no communication between MAC
165
and I/O device
102
.
However, when a link failure or interrupt occurs along the primary link, the system must switch over to the redundant (or backup) link. For the purposes of the example given above, this means that the system must shut down (or set to idle) the primary link between primary MAC
160
and I/O device
102
and switch over to the redundant link between the redundant MAC
165
and I/O device
102
. This “switch-over” is sometimes done using a software algorithm, for example Spanning Tree Protocol, which takes a long time, i.e. a few to several seconds, to switch from the broken or interrupted link to the redundant or backup link. On a high-speed link, such as a Gigabit Ethernet, a few to several seconds may equate to a large amount of traffic lost at the core of the enterprise network.
Thus, what is needed is a method and system for supporting redundant links with fast switch-over times.
SUMMARY OF THE INVENTION
A method and apparatus for a media access controller supporting redundant links are described. According to one aspect of the present invention a media access controller includes a two transceivers for communication with an source and/or destination port. Each transceiver has a receiver and transmitter. When the media access controller sets up a physical link to the desired source and/or destination port each transceiver sets up a separate physical link to the source and/or destination port. One of the physical links is the primary physical link and the other is a redundant or backup physical link. By using two physical links if a failure of interrupt occurs on the primary physical link then a switch-over is performed to use the redundant physical link.
Additional features and benefits of the present invention will become apparent from the detailed description, figures, and claims set forth below.
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patent: 4964120 (1990-10-01), Mostashari
patent: 5249183 (1993-09-01), Wong
patent: 5485576 (1996-01-01), Fee
patent: 5487062 (1996-01-01), Yanagi et al.
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patent: 6081511 (2000-06-01), Carr
Blakely , Sokoloff, Taylor & Zafman LLP
Ngo Ricky
Nortel Networks Limited
Tran Phuc
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