Congestion Control

1. 1
Congestion
Control in
Computer
Networks

2. 2
Presented By
1.Sauda Tus Sahadia
2.Shantanu Mandal
3.Md Azom Uddin
4.Abu Sayed Abdullah
5.Maria Islam

3. 3
Introducti
on
• Too much data being sent at once,
slowing down the network.
• Similar to traffic congestion on
roads.
What is Congestion?
• a crucial concept in computer
networks
• A methods used to prevent network
overload
• ensure smooth data flow
What is Congestion
control?

4. 4
Effects of
Congestio
n Control
Improved Network Stability: Prevents network failures.
Reduced Latency & Packet Loss: Ensures smooth and
fast data transfer.
Enhanced Throughput: Optimizes network resource
usage.
Fair Resource Allocation: Ensures equal bandwidth
distribution.
Better User Experience: Faster browsing, seamless
applications.
Prevention of Network Collapse: Avoids severe
slowdowns due to congestion.

5. 5
Congestion
Control
Mechanism
s
Open-Loop
Control
Closed-
Loop
Control

6. 6
Open-Loop Congestion Control (Prevention)
Prevent congestion by controlling data flow at the source.
Goal
1.No feedback mechanism.
2.Static policies control data transmission.
3.Works best in predictable network conditions
Characteristics:
• Traffic Shaping (Leaky Bucket, Token Bucket)
• Resource Reservation
• Admission Control
• Packet Scheduling
Example techniques:

7. 7
Traffic Shaping
Techniques (for
Open-Loop Control)
• Packets are sent at a fixed
rate.
• Prevents bursts but may cause
delays.
Leaky Bucket
Algorithm:
• Allows bursts but limits overall
traffic rate.
• More flexible than Leaky
Bucket.
Token Bucket
Algorithm:

8. 8
Leaky
Bucket
Algorithm
Concept
• Controls traffic flow at a constant rate.
Example
• A bucket leaks at a steady rate; excess
water (data) spills.
Steps
1.Packets enter a finite-size bucket.
2.Packets are transmitted at a fixed rate.
3.Burst traffic is converted into steady traffic.
Disadvantages:
Inefficient use of bandwidth.

9. 9
Token Bucket
Algorithm
Concept
• Allows burst traffic while
maintaining overall control.
Steps
1.Tokens are generated
periodically in a bucket.
2.Packets consume tokens before
being sent.
3.If no tokens, packets must wait.
Advantages
• Flexible & prevents packet
loss.

10. 10
Closed-Loop Congestion Control (Reaction)
Goal:
Detect and respond to
congestion
dynamically.
Characteristics
:
Uses feedback from
the network.
Dynamically adjusts
transmission rates.
Works best in dynamic,
changing conditions.
Example
techniques:
Backpressure
Choke Packets
Explicit Congestion
Notification (ECN)
TCP Congestion
Control

11. 11
Choke
Packets
Definition: Special control packets sent by a router to
notify a sender of congestion.
How It Works:
1. Router detects congestion.
2. Sends a choke packet to the sender.
3. Sender reduces transmission rate.
4. If congestion persists, more choke packets are
sent.
Key Benefit: Quickly prevents overload without
dropping packets.

12. 12
Open-Loop vs. Closed-
Loop Comparison

13. 13
Advantages
of
Congestion
Control
Stable Network Operations
Reduced Delays & Data Loss
Efficient Resource Utilization
Scalability & Adaptability

14. 14
Disadvantag
es of
Congestion
Control
Complexity in
Implementati
on
Overhead on
Network
Resources
Sensitivity to
Network
Conditions
Challenges in
Fair Resource
Allocation

15. 15
Conclusion
Congestion control is
essential for network
performance.
Algorithms like Leaky Bucket
& Token Bucket help
manage data flow.
Proper control ensures a
stable, fast, and reliable
network.

16. 16
Thank You