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Zorluk: ZorUtilizing Hardware Testers and Packet Analyzers

A network technician is troubleshooting severe packet loss and link flapping on a 60-meter Category 6 UTP cable drop connecting a workstation to a access switch. A basic wiremap tester indicates that all eight conductors maintain correct end-to-end pin continuity with no open or short circuits. However, when testing the link with a Time-Domain Reflectometer (TDR), the device indicates a significant signal reflection and impedance anomaly at exactly 32 meters from the local patch panel. Which of the following physical cable conditions is the TDR identifying that the basic wiremap tester failed to detect?

  1. A physical deformation, such as a sharp bend radius violation or severe cable kink, that alters pair geometry and characteristic impedance without severing pin continuityCevap
  2. B
    A total open circuit across conductor pair 4/5 at the 32-meter mark that completely interrupts DC current flow between endpoints
  3. C
    An OSI Layer 3 packet encapsulation failure caused by corrupt Layer 2 Ethernet frame headers passing through the cable drop
  4. D
    A service port mismatch between TCP port 67 and UDP port 68 during the physical layer link establishment negotiation

Cevap

The TDR identifies a physical deformation, such as a sharp bend or severe kink in the cable run, that alters characteristic impedance without breaking DC continuity.
The correct answer explains that a Time-Domain Reflectometer (TDR) transmits electrical pulses along a conductor and measures reflections caused by changes in characteristic impedance. A physical defect such as a kink or severe bend alters the spacing between twisted pairs, creating an impedance mismatch at that location (32 meters) without severing the conductor. This causes high return loss and link degradation at high data rates while passing basic wiremap DC continuity tests.

Adım Adım Çözüm

1
Analyze the diagnostic capabilities of a basic wiremap tester versus a Time-Domain Reflectometer (TDR).
A wiremap tester only verifies pinout alignment and DC electrical continuity (detecting opens, shorts, and reversed pairs). It cannot measure signal reflections or impedance consistency.
Passing a wiremap test rules out complete conductor breaks or pin transposition errors.
2
Interpret the TDR measurement output of a signal reflection at 32 meters.
TDR sends electrical pulses down the cable; any change in characteristic impedance (such as from a kink, tight cable tie, or physical crush) reflects a portion of the pulse back to the source.
The time delay of the reflection determines the exact distance to the impedance anomaly.
3
Evaluate the underlying physical cause of high packet loss despite full continuity.
Impedance mismatches cause return loss and signal attenuation, which degrade high-speed signals (like 1000BASE-T) while allowing low-frequency DC continuity checks to succeed.
Maintaining physical bend radius guidelines prevents impedance changes along twisted-pair runs.

Anahtar Kavram

Time-Domain Reflectometry (TDR) and Impedance Anomaly Detection
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Konular

Utilizing Hardware Testers and Packet Analyzers

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