Abstract: 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 “detect loop” 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.

Abstract: 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.