Browse Prior Art Database

Fibre Channel Standard Hub-Loop Redundancy for Higher RAS

IP.com Disclosure Number: IPCOM000111950D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 78K

Publishing Venue

IBM

Related People

Truestedt, HL: AUTHOR

Abstract

A traditional loop can fail if any of its components fail (i.e., one component failure can take down the entire loop unless a redundant path or dual loop is implemented - which can be costly).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Fibre Channel Standard Hub-Loop Redundancy for Higher RAS

      A traditional loop can fail if any of its components fail
(i.e., one component failure can take down the entire loop unless a
redundant path or dual loop is implemented - which can be costly).

Described is a mechanism which provides redundancy without
duplication.

      For the emerging ANSI Fibre Channel Standard (FCS), one of the
physical topology options for a low-cost version is a HUB-LOOP.
HUB-LOOPs provide benefits over the traditional loop in that devices
can be hot-plugged or turned off-line, and additional performance is
realized.  Also, the device on such a loop requires certain special
characteristics (e.g., if it "sees" a frame which has a different
address than the device address, it passes the frame on) which the
normal FCS-attached device does not have.  A HUB-LOOP shields the end
device so that the attachment to the loop is transparent.

      Consider the following traditional loop structure (Note: only
four devices are shown for brevity; the FCS FABRIC and Loop Port
connection may or may not be present.):

      Each device looks at the incoming frame and, if it is not one
that is expected (i.e., the correct address), the device sends the
frame to the next device on the loop.  If the device is off-line,
needs to be removed, or the loop breaks, the entire loop is
non-operational.

      Now, consider the HUB-LOOP (Note: only four devices are shown
for brevity; the FCS FABRIC connection may or may not be there.):

      From a device point-of-view, the HUB-LOOP can be completely
transparent device; i.e., there is no difference from being attached
directly to the FCS Fabric.

The f...