SuperStack(TM) II Hub 100 T4 User Guide Release Notes

Modified: 11/06/96

Release Notes for the SuperStack II Hub 100 T4 User Guide

P/N 09-0971-001/August 1996

Introduction

These release notes provide information on the following topics:

o Management Unit reporting of Short Events in a mixed media hub stack

o Link LED indicator with high-traffic network devices

o Availability of the T4 transceiver interface module

o Compatibility information for the 100BASE-FX transceiver interface module

o Changes to the SuperStack(TM) II Hub 100 T4 User Guide

Short Event Reporting in a Mixed Media Hub Stack

In a mixed media stack (hub stack with both 100BASE-T4 and 100BASE-TX repeater units), the Short Event and Runt Frames statistics reported by the SuperStack II Hub 100 Management Unit may be inaccurate. Some Short Events may be reported as Runt Frames, but all Short Events reported are actually Short Events.

The IEEE 802.3u specification for Fast Ethernet defines the types and sizes of valid Ethernet frames for 100BASE-TX and 100BASE-T4 signaling. A Short Event is an invalid Ethernet frame smaller in size than a Runt Frame. The minimum event size threshold value (the number of bit times) that defines a Short Event differs between 100BASE-TX and 100BASE-T4 signaling. The SuperStack II Hub 100 Management Unit detects and reports Short Events and Runt Frames with other repeater statistics.

In a homogeneous hub stack (one made up of all 100BASE-T4 or all 100BASE-TX repeater units), the Management Unit detects the signaling used by the hub stack and sets the appropriate event size threshold value for Short Events. In a mixed media hub stack (containing 100BASE-T4 and 100BASE-TX repeater units), the Management Unit sets the smaller frame size threshold value.

Link LED Indicator

The link LED of the SuperStack Hub 100 T4 may not be lit when the hub is connected to a high-traffic network device such as a bridge, router, or switch, even though the link LED of the network device may indicate that a connection has been established. When this happens, the network device is sending packets to a disabled Hub 100 T4 port. To rectify this condition, momentarily disable the port on the high-traffic device. This permits sufficient time for both devices to establish a proper network link.

High-traffic network devices such as bridges, routers, and switches may not have enough idle time on the network link to generate the correct number of pulses required by the Hub 100 T4 repeater unit to enable the link.

Transceiver Interface Module Availability

The 100BASE-T4 model of the SuperStack II Hub 100 transceiver interface module, part number 3C252-T4, is not available as of the date of these release notes. Please check with your 3Com reseller for availability information in your area.

Compatibility Information for the 100BASE-FX Transceiver Interface Module

Early versions of the SuperStack II Hub 100 100BASE-FX transceiver interface module (part number 3C262-FX) are not compatible with the SuperStack II Hub 100 T4. These modules can be identified by the following assembly numbers stenciled along the top of the component side of the modules circuit board:

o 03-0058-000-Rev A

o 03-0058-000-Rev B

o 03-0058-001-Rev A

Changes to the User Guide

Pages 1-4 and 1-5 of the user guide state that the LinkBuilder¨ FMSª 100 Management Unit can manage a Hub 100 T4 or a mixed media hub stack. Only the SuperStack II Hub 100 Management Unit can manage a SuperStack II Hub 100 T4.

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