Methods and apparatus for dynamic topology configuration in a

Abstract

A loop isolation circuit (LIC) to enable subdivision of a single daisy-chained communication loop (e.g., FC-AL) into smaller loops and to enable joining of smaller loops into a single larger loop. An LIC comprises essentially two multiplexors configured so as to permit controlled subdivision or joining of two loop portions. In a first selected state, the LIC subdivides a communication loop in which it is inserted into two loops. This configuration sacrifices accessibility among some devices previously on the larger loop for the benefit of enhanced bandwidth and reduced overhead due to node count. Bandwidth is enhanced by enabling simultaneous operation of two (or more) loop portions for establishing and communicating over logical circuit connections. However, when a failure of a redundant loop precludes access to devices, the LIC may be set to a second state to rejoin previously subdivided loops into a larger loop. This configuration restores access among all devices sharing common access to the larger loop. The LIC of the present invention therefore enables communication loop controllers to dynamically reconfigure a daisy-chained loop communication system to enhance performance in normal operation. The LIC of further enables restoration of the larger loop to restore redundant loop configurations. The LIC of the present invention is applicable in many daisy-chained loop communication environments including, but not limited to, Fiber Channel Arbitrated Loop (FC-AL).