Lab 16 — Network Performance, Latency and Packet Loss Analysis

Mission Information

Item	Details
Lab	16
Lab Name	Network Performance, Latency and Packet Loss Analysis
Track	CompTIA Network+
Difficulty	Intermediate
Estimated Time	120–150 minutes
Primary Role	Network Technician / Junior Network Administrator
Environment	Network+ Enterprise Performance Lab
Primary Systems	NETPLUS-CLIENT01, NETPLUS-SERVER01, NETPLUS-RTR01, NETPLUS-SW01
Primary Tools	Ping, Traceroute/Tracert, PathPing, iperf3, Wireshark, PowerShell, Linux Network Utilities
Skills	Latency, Packet Loss, Jitter, Bandwidth, Throughput, Retransmissions, Interface Errors, Congestion, Baselining, Performance Troubleshooting

Mission Objective: Measure network performance, establish a healthy baseline, deliberately introduce common performance problems, analyze their symptoms, identify bottlenecks, and determine whether degradation originates from the client, network path, interface, congestion, packet loss, or application.

Mission Scenario

The GHC Enterprise network is operational.

Users can:

Resolve DNS
     ↓
Reach Servers
     ↓
Connect to Services
     ↓
Access Applications

However, the help desk receives several complaints:

"The network is slow."

"File transfers take too long."

"Video calls keep freezing."

"The application works but responds slowly."

"Sometimes packets are dropped."

"Performance becomes worse during busy hours."

Basic testing shows:

Ping:
Successful

and:

Application:
Available

This means the investigation is no longer simply:

Does it work?

You now need to determine:

How well does it work?

Your investigation will move through:

Connectivity
     ↓
Latency
     ↓
Packet Loss
     ↓
Jitter
     ↓
Bandwidth
     ↓
Throughput
     ↓
Interface Health
     ↓
Congestion
     ↓
Application Performance

Mission Objectives

By completing this lab, you will be able to:

understand network performance metrics
distinguish bandwidth from throughput
measure latency
identify packet loss
understand jitter
establish network baselines
use continuous ping testing
use tracert and traceroute
use pathping
use iperf3
measure TCP throughput
measure UDP performance
analyze packet loss
analyze jitter
identify TCP retransmissions
inspect switch/router interface counters
identify interface errors
understand duplex mismatches
recognize congestion
identify bottlenecks
compare healthy and degraded performance
document performance findings
follow a structured troubleshooting workflow

1. Build the Performance Lab

Use:

NETPLUS-CLIENT01
10.10.10.20
      |
      |
NETPLUS-SW01
      |
      |
NETPLUS-RTR01
      |
      |
NETPLUS-SERVER01
10.10.20.30

This provides a routed path:

CLIENT01
   ↓
Switch
   ↓
Router
   ↓
Server

2. Verify Client Configuration

On CLIENT01:

ipconfig /all

Record:

IPv4 Address:

Subnet Mask:

Default Gateway:

DNS Server:

Interface Speed:

3. Verify Server Configuration

On Linux SERVER01:

ip addr

Then:

ip route

Record:

IP Address:

Default Gateway:

Interface:

4. Verify Basic Connectivity

From CLIENT01:

ping 10.10.20.30

Expected:

Reply

Do not begin performance analysis until basic connectivity is established.

5. Understand Network Performance

Network performance is influenced by several measurements:

Bandwidth

Throughput

Latency

Packet Loss

Jitter

Utilization

Errors

Retransmissions

These metrics describe different characteristics.

6. Understand Bandwidth

Bandwidth represents the theoretical or configured capacity of a network connection.

Examples:

100 Mbps

1 Gbps

10 Gbps

Conceptually:

Bandwidth
=
Maximum Potential Capacity

7. Understand Throughput

Throughput represents the amount of useful data actually transferred during a period of time.

Example:

Link Capacity:
1 Gbps

Measured Transfer:
620 Mbps

Therefore:

Bandwidth:
1 Gbps

Throughput:
620 Mbps

8. Bandwidth vs Throughput

Remember:

Bandwidth
≠
Throughput

A useful analogy:

Bandwidth
=
Size of the Road

Throughput
=
Actual Traffic Moving on the Road

Throughput can be affected by:

congestion
packet loss
protocol overhead
latency
retransmissions
device performance
server performance
wireless conditions
security inspection

9. Understand Latency

Latency measures how long data takes to travel across the network.

It is commonly measured in:

Milliseconds

or:

ms

Example:

CLIENT01
      ↓
10 ms
      ↓
SERVER01

10. Understand Round-Trip Time

Ping commonly reports:

Round-Trip Time

or:

RTT

Conceptually:

CLIENT
   ↓
Request
   ↓
SERVER
   ↓
Reply
   ↓
CLIENT

The total time is the RTT.

11. Measure Baseline Latency

From CLIENT01:

ping 10.10.20.30

Record:

Minimum:

Maximum:

Average:

Packet Loss:

Example:

Minimum = 2 ms

Maximum = 4 ms

Average = 3 ms

12. Run Extended Ping

Windows:

ping 10.10.20.30 -n 50

Linux:

ping -c 50 10.10.20.30

Record the results.

13. Create a Latency Baseline

Use:

Metric	Baseline
Minimum RTT
Maximum RTT
Average RTT
Packet Loss
Test Time

This becomes your:

Healthy Baseline

14. Why Baselining Matters

Without a baseline:

Latency = 45 ms

does not necessarily tell you whether there is a problem.

If normal performance is:

5 ms

then:

45 ms

is significant.

But if the normal WAN latency is:

40–50 ms

then 45 ms may be expected.

Therefore:

Performance measurements require context.

15. Understand Packet Loss

Packet loss occurs when packets fail to reach their intended destination.

Example:

100 Packets Sent

95 Received

5 Lost

Packet loss:

5%

16. Calculate Packet Loss

Formula:

Packet Loss %
=
Packets Lost
────────────── × 100
Packets Sent

Example:

5
─── × 100
100

=
5%

17. Why Packet Loss Matters

Packet loss can cause:

TCP Retransmissions

Slow File Transfers

Voice Problems

Video Freezing

Application Delays

Connection Failures

Even relatively small amounts of loss can noticeably affect some real-time applications.

18. Understand Jitter

Jitter is:

Variation in Packet Delay

Example:

Packet 1:
10 ms

Packet 2:
11 ms

Packet 3:
60 ms

Packet 4:
12 ms

The network may have acceptable average latency but poor:

Latency Consistency

19. Why Jitter Matters

Jitter is especially important for:

VoIP

Video Conferencing

Streaming

Real-Time Applications

High jitter may cause:

Audio Breakup

Video Freezing

Choppy Communication

20. Run Continuous Latency Testing

Windows:

ping 10.10.20.30 -t

Stop using:

Ctrl+C

Observe whether latency remains stable.

21. Analyze Latency Variation

Example:

Reply:
3 ms

Reply:
4 ms

Reply:
3 ms

Reply:
85 ms

Reply:
4 ms

This may indicate:

Transient Congestion

Queueing

Wireless Interference

CPU Load

Path Changes

depending on the environment.

22. Understand ICMP Limitations

Ping uses:

ICMP

Ping is useful, but:

Ping Performance
≠
Application Performance

Some networks:

deprioritize ICMP
rate-limit ICMP
block ICMP
treat application traffic differently

Use multiple measurements.

23. Investigate the Network Path

Windows:

tracert 10.10.20.30

Linux:

traceroute 10.10.20.30

Record each hop.

24. Understand Traceroute

Traceroute attempts to reveal routers along a path.

Example:

CLIENT01
   ↓
10.10.10.1
   ↓
10.10.50.1
   ↓
10.10.20.1
   ↓
SERVER01

This helps identify where a path changes or where investigation should continue.

25. Record the Route

Use:

Hop	Address	RTT
1
2
3
4

26. Understand TTL

Traceroute relies heavily on:

TTL

or:

Time To Live

Each Layer 3 hop decreases TTL.

When:

TTL = 0

a router normally discards the packet and may return an ICMP message.

Traceroute uses this behavior to discover hops.

27. Investigate Path Performance with PathPing

Windows:

pathping 10.10.20.30

PathPing combines concepts from:

Ping
+
Traceroute

and can provide packet-loss statistics across the path.

28. Interpret PathPing Carefully

Suppose:

Hop 1:
0% Loss

Hop 2:
30% Loss

Hop 3:
0% Loss

Destination:
0% Loss

Do not automatically conclude:

Hop 2 is dropping 30% of forwarded traffic.

Routers may rate-limit responses sent by the router itself while continuing to forward transit traffic normally.

Look for loss that continues:

Beyond the Hop

29. Install iperf3

On SERVER01:

sudo apt update
sudo apt install iperf3

On another supported Linux system:

sudo dnf install iperf3

Use the appropriate package manager for your lab OS.

30. Start the iperf3 Server

On SERVER01:

iperf3 -s

Default iperf3 server port:

TCP 5201

31. Verify the iperf3 Listener

Run:

ss -tln

Look for:

:5201

32. Run a TCP Throughput Test

From an iperf3 client:

iperf3 -c 10.10.20.30

Record:

Transfer:

Bitrate:

Retransmissions:

33. Understand iperf3 Output

Example:

Transfer:
1.10 GBytes

Bitrate:
945 Mbits/sec

This represents measured:

TCP Throughput

between the test systems.

34. Run a Longer Test

iperf3 -c 10.10.20.30 -t 30

A longer test may reveal:

Performance Fluctuation

Congestion

Retransmissions

Sustained Throughput

35. Run a Reverse Test

Use:

iperf3 -c 10.10.20.30 -R

This reverses the test direction.

Compare:

CLIENT → SERVER

with:

SERVER → CLIENT

36. Why Direction Matters

A network problem may affect:

Upload

differently from:

Download

because paths, policies, congestion, shaping, or interface behavior may differ.

37. Run Parallel TCP Streams

Use:

iperf3 -c 10.10.20.30 -P 4

This creates multiple parallel streams.

Compare results with:

iperf3 -c 10.10.20.30

Do not assume multiple streams represent normal application behavior; they are a testing technique.

38. Test UDP Performance

Use:

iperf3 -c 10.10.20.30 -u -b 10M

This requests approximately:

10 Mbps

of UDP traffic.

39. Analyze UDP Results

UDP tests can report:

Bitrate

Jitter

Lost Datagrams

Total Datagrams

Packet Loss %

These metrics are useful for real-time traffic analysis.

40. Record UDP Baseline

Use:

Metric	Result
Target Bitrate
Measured Bitrate
Jitter
Lost Datagrams
Packet Loss

41. Increase UDP Load

Test:

iperf3 -c 10.10.20.30 -u -b 50M

Then:

iperf3 -c 10.10.20.30 -u -b 100M

Only increase traffic within the capacity of your isolated lab.

42. Compare UDP Results

Look for changes in:

Packet Loss

Jitter

Throughput

As offered load approaches or exceeds available capacity, degradation may become visible.

43. Understand Congestion

Congestion occurs when:

Traffic Demand
>
Available Capacity

Conceptually:

100 Mbps Link
      ↓
150 Mbps Offered Traffic
      ↓
Queues
      ↓
Delay
      ↓
Drops
      ↓
Retransmissions

44. Congestion Symptoms

Common symptoms include:

Increasing Latency

Packet Loss

Jitter

Lower Throughput

TCP Retransmissions

Queue Drops

45. Simulate Congestion

In the isolated lab, generate a sustained iperf3 transfer:

iperf3 -c 10.10.20.30 -t 60

While it runs, from another terminal:

ping 10.10.20.30

Compare latency with the baseline.

46. Record Congestion Results

Use:

Metric	Baseline	Under Load
Average RTT
Maximum RTT
Packet Loss
Throughput

47. Understand Queueing Delay

When interfaces become busy:

Packets Arrive
     ↓
Interface Busy
     ↓
Packets Wait in Queue
     ↓
Latency Increases

This is:

Queueing Delay

48. Understand Bufferbloat

Excessive queueing can produce:

High Latency

even when packets are not immediately dropped.

This behavior is commonly associated with:

Bufferbloat

Typical symptom:

Idle Network:
Low Latency

Busy Network:
Very High Latency

49. Capture Traffic During Performance Testing

Start Wireshark.

Filter:

tcp.port == 5201

Run:

iperf3 -c 10.10.20.30

Observe the TCP stream.

50. Look for TCP Retransmissions

Wireshark filter:

tcp.analysis.retransmission

Record:

Number of Retransmissions:

Source:

Destination:

Timestamp:

51. Understand TCP Retransmission

TCP retransmits when expected data or acknowledgments are not successfully accounted for.

Conceptually:

Sender
   ↓
Packet
   ↓
X Lost
   ↓
No Expected ACK Progress
   ↓
Retransmission

Retransmissions reduce useful throughput.

52. Look for Duplicate ACKs

Wireshark:

tcp.analysis.duplicate_ack

Duplicate acknowledgments can be associated with missing or out-of-order TCP segments.

Interpret them within the entire flow.

53. Look for TCP Out-of-Order Packets

Filter:

tcp.analysis.out_of_order

Possible causes include:

Multipath Routing

Capture Artifacts

Packet Reordering

Network Conditions

Do not assume every out-of-order indication represents packet loss.

54. Use Wireshark TCP Stream Graphs

Where available:

Statistics
   ↓
TCP Stream Graphs

Explore graphs such as:

Throughput

Round Trip Time

Time Sequence

These provide visual performance information.

55. Inspect Switch Interface Counters

On a Cisco-like switch:

show interfaces

Look for:

Input Errors

CRC Errors

Frame Errors

Output Errors

Drops

Collisions

Interface Resets

56. Inspect a Specific Interface

Example:

show interfaces gigabitEthernet0/1

Record:

Status:

Line Protocol:

Speed:

Duplex:

Input Rate:

Output Rate:

Input Errors:

CRC:

Output Errors:

Drops:

57. Understand Interface Utilization

Example:

Interface:
1 Gbps

Current Traffic:
950 Mbps

Approximate utilization:

95%

Sustained high utilization may contribute to congestion.

58. Calculate Interface Utilization

Formula:

Utilization %
=
Current Traffic Rate
──────────────────── × 100
Interface Capacity

Example:

800 Mbps
──────── × 100
1 Gbps

=
80%

59. Understand CRC Errors

CRC errors can indicate corrupted Ethernet frames.

Possible causes include:

Damaged Cable

Bad Connector

Electrical Interference

Faulty Interface

Physical Layer Problems

An increasing CRC counter deserves investigation.

60. Understand Input Errors

Input errors may include several receive-side problems.

Investigate:

Physical Medium

NIC

Transceiver

Duplex

Interface Health

Error Counters

61. Understand Output Drops

Output drops can occur when:

Packets Arrive Faster
Than Interface Can Transmit

Possible cause:

Congestion

62. Understand Duplex

Ethernet interfaces may operate as:

Half Duplex

or:

Full Duplex

Modern switched Ethernet generally uses:

Full Duplex

63. Understand Duplex Mismatch

A duplex mismatch can occur when:

Side A:
Full Duplex

Side B:
Half Duplex

Possible symptoms include:

Poor Throughput

Errors

Collisions

Retransmissions

Intermittent Performance

64. Check Interface Speed and Duplex

Cisco-like:

show interfaces status

or:

show interfaces

Verify:

Speed

Duplex

65. Understand Auto-Negotiation

Modern Ethernet commonly uses:

Auto-Negotiation

to determine capabilities such as speed and duplex.

Problems may occur when:

One Side Forced
+
Other Side Auto

depending on equipment and configuration.

66. Troubleshooting Scenario 1 — High Latency

Baseline:

Average:
3 ms

Current:

Average:
85 ms

Investigate:

Congestion

Interface Utilization

Path Changes

Wireless Conditions

Device CPU

Queueing

67. Troubleshooting Scenario 2 — Packet Loss

Results:

Packets Sent:
100

Received:
92

Lost:
8

Calculate:

8% Packet Loss

Investigate:

Interface Errors

Congestion

Wireless Signal

Physical Layer

Routing Stability

Firewall / Policing

68. Troubleshooting Scenario 3 — High Jitter

Results:

10 ms

11 ms

75 ms

12 ms

90 ms

10 ms

Average latency alone may hide the problem.

Investigate:

Queueing

Congestion

Wireless Interference

Unstable Path

69. Troubleshooting Scenario 4 — Low Throughput

Link:

1 Gbps

iperf3 result:

85 Mbps

Do not immediately blame bandwidth.

Check:

Interface Speed

Duplex

Packet Loss

Retransmissions

CPU

Congestion

Traffic Shaping

Intermediate Links

70. Troubleshooting Scenario 5 — Interface Negotiated at 100 Mbps

Expected:

1 Gbps

Actual:

100 Mbps

Possible causes:

Cable Problem

NIC Limitation

Switch Configuration

Auto-Negotiation Problem

Physical Pair Failure

71. Troubleshooting Scenario 6 — Increasing CRC Errors

Run:

show interfaces

Record CRC count.

Generate traffic.

Run it again.

If:

CRC Counter
Continues Increasing

investigate the physical path.

72. Troubleshooting Scenario 7 — Congested Interface

Interface:

Capacity:
100 Mbps

Traffic:
98 Mbps

Symptoms:

High Latency

Queue Drops

Jitter

Reduced Application Performance

Root cause may be:

Link Saturation

73. Troubleshooting Scenario 8 — TCP Retransmissions

Wireshark shows many:

TCP Retransmissions

Possible areas:

Packet Loss

Congestion

Wireless Quality

Physical Errors

Path Problems

Retransmission is a symptom.

Find the underlying cause.

74. Troubleshooting Scenario 9 — Application Slow but Network Healthy

Results:

Latency:
Normal

Packet Loss:
0%

iperf3:
Normal

Interfaces:
Healthy

but:

Application:
Slow

Your network evidence suggests investigation should move toward:

Application Server

Database

Storage

CPU

Memory

Application Configuration

This is an important troubleshooting conclusion.

75. Troubleshooting Scenario 10 — Network Slow Only During Peak Hours

Baseline:

08:00:
Normal

Peak period:

14:00:
Slow

Investigate:

Utilization

Concurrent Users

WAN Usage

Backups

Large Transfers

Cloud Synchronization

Scheduled Jobs

This demonstrates the value of:

Time-Based Baselining

76. Understand Bottlenecks

A bottleneck is a component that limits overall performance.

Example:

CLIENT
1 Gbps
   ↓
SWITCH
1 Gbps
   ↓
WAN
100 Mbps
   ↓
SERVER
1 Gbps

Maximum end-to-end capacity is constrained by:

100 Mbps WAN Link

77. Find the Slowest Link

Remember:

End-to-End Performance

can be limited by:

Slowest Link

Congested Link

Lossy Link

Slow Endpoint

78. Understand MTU Performance Issues

MTU means:

Maximum Transmission Unit

Incorrect MTU or path-MTU problems may produce:

Fragmentation

Dropped Large Packets

VPN Problems

Application Performance Issues

79. Check MTU

Windows:

netsh interface ipv4 show subinterfaces

Linux:

ip link show

Record the MTU.

80. Test Packet Size

Windows example:

ping 10.10.20.30 -f -l 1400

Increase carefully within the lab to understand path-MTU behavior.

-f requests Don’t Fragment behavior for IPv4 on Windows.

81. Understand QoS

QoS stands for:

Quality of Service

QoS can prioritize traffic based on business requirements.

Examples:

Voice

Video

Business-Critical Applications

over lower-priority traffic.

82. Why QoS Matters

During congestion:

Voice
+
Backup
+
File Transfer

all compete for bandwidth.

QoS can help ensure:

Latency-Sensitive Traffic

receives appropriate treatment.

QoS does not create additional bandwidth.

83. Understand Traffic Shaping

Traffic shaping controls traffic rates by:

Buffering

Delaying

Scheduling

traffic to conform to configured policies.

84. Understand Traffic Policing

Traffic policing may:

Permit Traffic Within Rate

and:

Drop / Remark Traffic
Beyond Policy

depending on configuration.

85. Shaping vs Policing

Conceptually:

Shaping
=
Delay Excess Traffic

Policing
=
Enforce Rate

The exact behavior depends on the implementation.

86. Build a Performance Baseline

Collect healthy-state measurements:

Latency

Packet Loss

Jitter

TCP Throughput

UDP Throughput

Interface Utilization

Interface Errors

Retransmissions

87. Create the Baseline Table

Metric	Normal Result
Average Latency
Maximum Latency
Packet Loss
Jitter
TCP Throughput
UDP Throughput
Interface Utilization
CRC Errors
TCP Retransmissions

88. Compare Healthy vs Degraded

Use:

Metric	Healthy	Degraded
Latency
Packet Loss
Jitter
Throughput
Retransmissions
Interface Errors
Utilization

89. Mission Challenge — Bandwidth vs Throughput

Interface:

1 Gbps

Measured transfer:

650 Mbps

Identify:

Bandwidth:
1 Gbps

Throughput:
650 Mbps

90. Mission Challenge — Calculate Packet Loss

Sent:

Received:

Lost:

Calculation:

10
─── × 100
200

=
5%

91. Mission Challenge — Identify Jitter

Measurements:

10 ms

11 ms

9 ms

85 ms

10 ms

Primary concern:

Latency Variation

or:

Jitter

92. Mission Challenge — Identify Congestion

Symptoms:

Normal Latency:
5 ms

Under Load:
150 ms

Interface Utilization:
98%

Likely area:

Congestion / Queueing

93. Mission Challenge — Physical Layer Problem

Symptoms:

Low Throughput

Increasing CRC Errors

Packet Loss

First investigate:

Cable

Connector

Transceiver

NIC

Switch Port

94. Mission Challenge — Duplex Problem

Symptoms:

Connectivity:
Working

Performance:
Poor

Errors:
Increasing

Duplex:
Mismatch

Likely root cause:

Duplex Configuration

95. Mission Challenge — Slow Application

Measurements:

Ping:
Normal

Packet Loss:
0%

iperf3:
Normal

Interface Errors:
0

Application remains slow.

Your evidence suggests:

Network:
Likely Healthy

Escalate investigation toward:

Application / Server

96. Mission Challenge — Retransmissions

Wireshark shows:

Large Number of TCP Retransmissions

Do not conclude:

TCP is broken

Instead investigate why packets are being lost or delayed.

97. Mission Challenge — Path Problem

CLIENT01 reaches SERVER01 through:

Router A
   ↓
Router B
   ↓
Router C

Performance degrades after a routing change.

Compare:

Previous Traceroute

with:

Current Traceroute

Look for:

New Path

Additional Hops

Unexpected WAN Route

98. Build the Performance Troubleshooting Workflow

Use:

User Reports Slow Network
        ↓
Define the Symptom
        ↓
Check Scope
        ↓
One User or Many?
        ↓
Wired or Wireless?
        ↓
Local or Remote?
        ↓
Check Baseline
        ↓
Measure Latency
        ↓
Measure Packet Loss
        ↓
Measure Jitter
        ↓
Inspect Path
        ↓
Measure Throughput
        ↓
Check Interface Utilization
        ↓
Check Errors / Drops
        ↓
Analyze Retransmissions
        ↓
Identify Bottleneck
        ↓
Implement Fix
        ↓
Retest
        ↓
Compare with Baseline

99. Understand Scope

Before troubleshooting, determine:

One User?

or:

Entire Department?

or:

Entire Site?

or:

One Application?

or:

All Applications?

Scope significantly narrows the investigation.

100. Example Scope Analysis

If:

Only CLIENT01

is slow, investigate:

Client NIC

Cable

Switch Port

Local Configuration

If:

Entire VLAN

is slow, investigate:

VLAN Path

Uplink

Gateway

Shared Infrastructure

If:

Entire Site

is slow, investigate:

WAN

Internet Connection

Core Network

Shared Services

101. Create the Lab Workspace

On your administration workstation:

mkdir -p ~/NetworkPlus-Labs/LAB16/{Captures,Screenshots,Results,Notes}

Create:

touch ~/NetworkPlus-Labs/LAB16/Notes/lab16-notes.md

102. Save Performance Results

Store:

baseline-ping.txt

extended-ping.txt

traceroute.txt

pathping.txt

iperf3-tcp.txt

iperf3-reverse.txt

iperf3-parallel.txt

iperf3-udp.txt

interface-counters.txt

degraded-performance.txt

103. Save Packet Captures

Create:

LAB16-BASELINE.pcapng

LAB16-IPERF-TCP.pcapng

LAB16-RETRANSMISSIONS.pcapng

LAB16-CONGESTION.pcapng

LAB16-PACKET-LOSS.pcapng

104. Document Your Findings

Use:

# LAB16 — Network Performance, Latency and Packet Loss Analysis

## Environment

Client:

Client IP:

Server:

Server IP:

Network Path:

## Baseline

Average Latency:

Maximum Latency:

Packet Loss:

TCP Throughput:

UDP Throughput:

Jitter:

## Traceroute

Hop 1:

Hop 2:

Hop 3:

Destination:

## TCP Performance

Transfer:

Throughput:

Retransmissions:

## Reverse TCP Performance

Throughput:

## UDP Performance

Target Rate:

Measured Rate:

Jitter:

Packet Loss:

## Interface Analysis

Interface:

Speed:

Duplex:

Input Rate:

Output Rate:

Utilization:

Input Errors:

CRC Errors:

Output Errors:

Drops:

## Congestion Test

Baseline Latency:

Latency Under Load:

Packet Loss Under Load:

Throughput:

## Wireshark Analysis

TCP Retransmissions:

Duplicate ACKs:

Out-of-Order Packets:

## Troubleshooting Scenarios

### High Latency

Symptom:

Root Cause:

Fix:

### Packet Loss

Symptom:

Root Cause:

Fix:

### High Jitter

Symptom:

Root Cause:

Fix:

### Low Throughput

Symptom:

Root Cause:

Fix:

### CRC Errors

Symptom:

Root Cause:

Fix:

### Duplex Problem

Symptom:

Root Cause:

Fix:

### Congestion

Symptom:

Root Cause:

Fix:

## Final Assessment

Summarize the network's performance health, identified bottlenecks, and recommended improvements.

105. Evidence to Capture

Capture:

01-performance-topology.png

02-client-ip-configuration.png

03-server-ip-configuration.png

04-baseline-ping.png

05-extended-ping.png

06-latency-statistics.png

07-traceroute.png

08-pathping.png

09-iperf-server.png

10-iperf-tcp-test.png

11-iperf-reverse-test.png

12-iperf-parallel-test.png

13-iperf-udp-test.png

14-udp-jitter.png

15-udp-packet-loss.png

16-congestion-ping.png

17-congestion-throughput.png

18-wireshark-iperf.png

19-tcp-retransmissions.png

20-duplicate-acks.png

21-interface-status.png

22-interface-utilization.png

23-interface-errors.png

24-crc-errors.png

25-speed-duplex.png

26-mtu-configuration.png

27-mtu-test.png

28-healthy-baseline.png

29-degraded-baseline.png

30-final-performance-comparison.png

106. Validation Checklist

Performance Fundamentals

Bandwidth understood
Throughput understood
Bandwidth vs throughput compared
Latency understood
RTT understood
Packet loss understood
Jitter understood
Utilization understood

Latency Analysis

Baseline ping completed
Extended ping completed
Minimum latency recorded
Maximum latency recorded
Average latency recorded
Latency variation analyzed

Path Analysis

Traceroute completed
Network hops documented
TTL concept understood
PathPing completed
Hop-loss results interpreted carefully

Throughput Testing

iperf3 server configured
TCP throughput measured
Reverse test completed
Parallel stream test completed
UDP test completed
UDP jitter measured
UDP packet loss measured

Packet Analysis

iperf traffic captured
TCP retransmissions investigated
Duplicate ACKs investigated
Out-of-order packets understood
TCP stream performance reviewed

Interface Analysis

Interface speed verified
Duplex verified
Input utilization reviewed
Output utilization reviewed
Input errors checked
CRC errors checked
Output errors checked
Drops checked

Performance Problems

High latency investigated
Packet loss investigated
Jitter investigated
Low throughput investigated
Congestion investigated
CRC errors investigated
Duplex mismatch understood
Speed negotiation problem understood
TCP retransmissions investigated
Application vs network performance distinguished

Advanced Concepts

Bottlenecks understood
MTU reviewed
QoS understood
Traffic shaping understood
Traffic policing understood
Bufferbloat understood
Queueing delay understood

Baselining

Healthy baseline created
Degraded measurements collected
Healthy vs degraded compared
Time-based performance considered

Documentation

Results saved
Packet captures saved
Screenshots captured
Performance table completed
Troubleshooting findings documented
Final assessment completed

107. Mission Review

You began with a network where:

Connectivity:
Working

but users reported:

Performance:
Poor

You learned that these are different questions:

Can the packet reach the destination?

versus:

How efficiently can the packet reach the destination?

You investigated:

Latency
   ↓
Packet Loss
   ↓
Jitter
   ↓
Bandwidth
   ↓
Throughput
   ↓
Retransmissions
   ↓
Interface Errors
   ↓
Congestion

You also established the relationship:

High Utilization
      ↓
Queueing
      ↓
Higher Latency
      ↓
Possible Drops
      ↓
TCP Retransmissions
      ↓
Lower Throughput
      ↓
Poor User Experience

Most importantly, you learned to compare current performance against:

Known-Good Baseline

instead of relying only on statements such as:

"The network feels slow."

The key lesson is:

Network performance troubleshooting requires measurement. Establish a baseline, measure latency, packet loss, jitter and throughput, inspect the path and interface health, identify the bottleneck, implement the fix, and then compare the results against the baseline.

Skills Developed

After completing this mission, you should be able to:

establish network performance baselines
measure latency
calculate packet loss
understand jitter
distinguish bandwidth from throughput
analyze network paths
use ping effectively
use traceroute and tracert
use PathPing
perform iperf3 TCP testing
perform iperf3 UDP testing
analyze TCP retransmissions
inspect interface utilization
identify CRC errors
recognize congestion
understand queueing delay
recognize duplex problems
investigate speed negotiation problems
identify network bottlenecks
understand MTU-related performance issues
explain basic QoS
distinguish network performance from application performance
document and compare healthy and degraded states

What’s Next?

Lab 17 — Network Monitoring with SNMP and Syslog

You can now answer:

Is the network reachable?

Are services available?

Is performance healthy?

But enterprise network teams cannot manually run:

ping

traceroute

iperf3

show interfaces

against every device continuously.

Networks require:

Monitoring

The next mission introduces:

SNMP
SNMP managers and agents
SNMP polling
SNMP OIDs
MIBs
SNMPv2c
SNMPv3
SNMP traps
Syslog
Syslog severity levels
centralized logging
interface monitoring
bandwidth monitoring
CPU monitoring
memory monitoring
availability monitoring
performance thresholds
alerting
baseline monitoring
proactive network operations

The progression becomes:

Build Network
      ↓
Validate Connectivity
      ↓
Validate Services
      ↓
Measure Performance
      ↓
Monitor Continuously
      ↓
Detect Problems
      ↓
Generate Alerts
      ↓
Troubleshoot Proactively

➡️ Next: Lab 17 — Network Monitoring with SNMP and Syslog