Cisco Technology, Inc.

John K Chen

Gordon Mackay

Robert Gregory Twiss

James P Rivers

Guenter E Roeck

Mark E Millet

Feisal Y Daruwalla

Santanu Sinha

Gregory Lee DeJager

James R Forster

Van Van Nguyen

Gopakumar Parameswaran

Joanna Qun Zang

Robert D Hastings

Joseph O'Donnell

Sean X Wang

Rita Ousterhout

In a system having a plurality of nodes such as Ethernet repeaters, coupled by communication links such as cables, systems and protocols are provided for detecting and/or breaking loops. In one aspect, in response to an added link, a repeater sends a 'detect loop' message containing its address to at least one neighbor. Each repeater which receives the 'detect loop' message, in turn, sends it to its own neighbor, with the lesser of the received address and its own address. A repeater which receives a &#x201c;detect loop&#x201d; message containing its own address declares itself a master loop breaker and can isolate one of its ports to break the loop. In one aspect, a previously intentionally-isolated port can be re-activated, e.g., in response to the loss of a communication link which could potentially isolate one or more nodes.

Method and apparatus to detect and break loop configuration

A CMTS redundancy technique requires at least two CMTS interfaces (e.g., line cards) on one or more CMTS chassis at the head end of a cable network. One of the CMTSs serves as a backup or 'protecting' CMTS. When another CMTS (a 'working' CMTS) becomes unavailable to service its group of cable modems, the protecting CMTS takes over service to those cable modems. The SWITCHOVER takes place transparently (or nearly transparently) to the cable modems. The protecting CMTS provides service on the same downstream channel as used by the working CMTS. The cable modems need not modify any settings pursuant to their cable modem communication protocol (e.g., DOCSIS ranging). This transparency to the cable modems is realized by keeping the working and protecting CMTSs in synchronization regarding service parameters for the cable modems. In other words, the protecting CMTS maintains a list of current parameters for allowing service to the cable modems.

Cable network redundancy architecture

A repeater, useable for connecting switches in a data communication network, is provided in a distributed and/or modular fashion. The repeater includes a plurality of separate and distinct components or modules connected to or at least partially housed in, the various switches which the repeater modules couple. The distributed and/or modular repeater facilitates accommodating various switching or repeater needs as a network grows or contracts. A light pipe, preferably integral with a module case, conveys indicator lights to a position visible when viewing a switch front panel. A heat spreader unit receives and/or conveys heat and/or protects against undue EMI. A collision-handling state machine transmits modified collision fragments so as to avoid reduction in interpacket gaps, e.g. by downstream repeater modules.

Distributed network repeater module and method

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Sunnyvale, CA, United States of America

John K Chen