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TAKUMI SUGATA
TAKUMI SUGATA

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Understanding the Evolution of CAT Standards Makes Memorization Unnecessary.

#beginners #learning #networking #tutorial

Introduction

While studying for CompTIA Network+, I couldn't remember CAT standards in LAN cable field.
The sheer number of specification made it difficult to answer related questions confidently.
Once I understand how each standard evolved from the previous one, everything clicked.

What is CAT standards

LAN cable has CAT (Category) standards, which shows that higher number perform better.
Understanding the logic behind each standard is more effective than memorizing numbers.

Why higher standard accelerates speed

LAN cables consist of 8 copper wires. Trying to increase signal speed introduced two key challenges.

Problem 1：Crosstalk
Receive electrical interference from the adjacent copper cables
→ Signal degrades

Problem 2：Attenuation 
Longer distance weakens signal
→ Not be able to reach
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The higher standards are designed to solve these problems.

What is the solution in each evolution stages

CAT5 → CAT5e 

Problem： Frequent Crosstalk
Solution： Twist Copper cables
Result：100Mbps → 1Gbps
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Twisting has an advantage to solve signal interference.

Rough twisting → More interference → slower
Fine twisting → Less interference → faster
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e shows Enhanced .

CAT5e → CAT6 

Problem： Pushing beyond 1Gbps increases susceptibility to Crosstalk
Solution： Introduce spine in a center of the cable and more twist
Result：1Gbps → 10Gbps
※10Gbps reaches under 55 meters
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** Why CAT6 cannot reach over 55 meters in using 10Gbps

Faster signal = Increase electrical interference
　↓
Longer distance can degrade the signal due to accumulation of interference
　↓
Over 55m cannot retain the speed of 10Gbps
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Without shielding, the cable is susceptible to outside interference.

CAT6 → CAT6a 

Problem：CAT6 cannot reach over 55m in 10Gbps
Solution： Wrap the cable by shield (metal shroud), which blocks outer interference
Result：55m (10Gbps) → 100m
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Without shield（CAT6）
→Influenced by outer electric devices 
→Longer distance degrades signal

With shield（CAT6a）
→Block outer interference
→Retain longer distance at 10Gbps
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a shows Augmented .

CAT6a → CAT7 

Problem：CAT6a still has interference at high frequencies between wire pairs 
Solution：Wrap each individual wire pair with its own shield
Result：Crosstalk between pairs reduced to nearly zeeo
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The difference between CAT6a and CAT7 lies in the shielding structure.

CAT6a：
┌─────────────────────────────────────┐
│ Whole Shield                        │
│  ○ ○ ○ ○（The pair without shield） │
└─────────────────────────────────────┘

CAT7：
┌───────────────────────────────────┐
│ Whole Shield                      │
│ [○][○][○][○]（Individual shield ）│
└───────────────────────────────────┘
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CAT7 → CAT8 

Problem： Lacking with 10Gbps for data center
Solution： Enforce the quality of copper cables and shield
Result：10Gbps → 40Gbps, but reach just 30m
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The reason why CAT8 can reach just 30m

High speed signal (40Gbps)
　↓
High electrical interference 
　↓
Shield cannot function to retain the signal strength for long distance
　↓
Use under 30m
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CAT8 is designed for connecting to server racks inside data center.

Server rack A ──── 30m ────→ Server rack B
　↓
The length is enough for data center 
　↓
It prioritize the speed rather than distance
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Why CAT5-CAT6a are the length of 100m

This is the reason for the designed standard.

The typical distance from one end of an office floor to the other is approximately 100m.
Ethernet standard is designed for architectural standard.

The edge of the office ──── 100m ────→ Server room
　↓
Ethernet standard can cover them
　↓
CAT5〜CAT6a = 100m
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Understanding whole structure 

Need for fast speed
　↓
Problem for interference and attenuation
　↓
Solution①：more twisted（CAT5e・CAT6）
Solution②：cover with whole shield（CAT6a）
Solution③：cover each pair with individual shield（CAT7）
Solution④：enhance the quality of materials and structure（CAT8）
　↓
The faster the speed, the greater the interference challenges become.
　↓
The limited distance for the fastest speed（CAT8の30m）
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Summary

Standard Speed Distance Improvement Use case
CAT5 100Mbps 100m Normal structure Traditional environment
CAT5e 1Gbps 100m Twist Copper cables Household・Office
CAT6 10Gbps 55m※ Introduce spine in a center of the cable Enterprise office
CAT6a 10Gbps 100m Wrap whole cable by shield Data center
CAT7 10Gbps 100m Wrap the individual cable by shield High performance enterprise network
CAT8 40Gbps 30m Enforce the quality of copper cables and shield Inside data center

※CAT6: 10Gbps can reach 55m, but 1Gbps can reach 100m.

Key numbers from the exam

CAT6  = 10Gbps → 55m (not 100m)
CAT6a = 10Gbps → 100m
CAT8            → 30m
All others      → 100m
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Conclusion

I used to struggle with these questions.
Each standard exists to solve a specific interference problem.
Once you understand that evolution, the numbers take care of themselves

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