Diagnosing Cable States Using Time Domain Reflectometry (Tdr); Time Domain Reflectometry On Acx Series Routers Overview - Juniper ACX1000 Configuration Manual

CHAPTER 36
Diagnosing Cable States Using Time
Domain Reflectometry (TDR)

Time Domain Reflectometry on ACX Series Routers Overview

Copyright © 2017, Juniper Networks, Inc.
Time Domain Reflectometry on ACX Series Routers Overview on page 1327
Diagnosing a Faulty Twisted-Pair Cable on ACX Series Routers on page 1330
Time Domain Reflectometry (TDR) is a technology used for diagnosing copper cable
states. This technique can be used to determine if cabling is at fault when you cannot
establish a link. TDR detects the defects by sending a signal through a cable, and reflecting
it from the end of the cable. Open circuits, short circuits, sharp bends and other defects
in the cable, reflects the signal back, at different amplitudes, depending on the severity
of the defect.
Several factors that result in degraded or low-quality cable plants can cause packet loss,
suboptimal connection speed, reduced network efficiency, and complete connection
failures. These types of problems can occur because of poor cable construction,
identification of pair twists, loose connectors, poor contacts between the points, and
stretched or broken pairs of cables. Broadcom transceivers enable you to analyze the
condition of the cable plant or topology and identify any problems that have occurred.
This functionality is effectively used in the following scenarios:
Troubleshooting during initial network equipment installation.
Discovery of failures when network problems occur.
Maintenance of optimally functioning cable plants.
Fault determination during the testing of network equipment in production cable
networks.
TDR supports the following capabilities for examination of cable faults on ACX Series
routers:
Cable status pair (open or short)—When the router operates in Gigabit Ethernet mode,
all the four pairs (8 wires) are used. Only Pair-A and Pair-B are required to operate in
10/100BASE-T Ethernet mode. If either of these required pairs is open or short-circuited,
the transceiver reports the following faults:
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