Fibre Channel Arbitrated Loop Hub User's Guide

This document is the User's Guide for the Digital StorageWorks Fibre Channel Arbitrated Loop Hub (DS-DHGGA-CA), published in October 1997.

The hub is an active hub designed to enhance Fibre Channel connectivity by collapsing a physical loop into a logical star, providing intelligent port bypass functions to manage nodes. This preserves data availability and prevents downtime from node failures, cable disconnections, or network reconfigurations. It supports a gigabit infrastructure and up to 126 devices.

Key functionalities include:

• Automatic Operation: The hub operates without user intervention, continuously monitoring serial data and automatically configuring the Fibre Channel Arbitrated Loop (FC-AL) in a plug-and-play manner. It is transparent to the protocol and does not consume FC-AL addresses.
• Active Repeaters: Each port re-drives and re-times input signals at 1.0625 Gbit/sec to attenuate jitter, allowing the use of various Fibre Channel compliant cables up to 10 meters.
• Intelligent Data Detection Checks (DDCs): It employs three continuous and simultaneous checks (DDC1 for invalid characters, DDC2 for oscillation, DDC3 for crosstalk) to ensure only valid Fibre Channel devices are connected to the loop, minimizing disruption.
• Asymmetric Port Bypass Sensitivity: The hub uses distinct "TimeOut" periods (200ms) to remove failed ports and "TimeIn" periods (100ms) to add new nodes, providing built-in hysteresis to prevent fault propagation and maintain loop stability.
• Fault Indicators: Front panel LEDs indicate port status (amber for bypassed, off for active) and power (green for on).

The guide also details the hub's configuration (internal port order), installation procedures (desktop mounting, DB-9 connectors, twinax cables), and power requirements (IEC 320 connector, no power switch, should be the first component powered up). Appendices provide regulatory notices (FCC, Industry Canada, CE Mark) and detailed hardware specifications (mechanical, electrical, power, environmental). The document notes that the product has no field-serviceable components, and opening it voids the warranty.