Congestion control

1. CONGESTION
CONTROL
GROUP MEMBER
TABASSUM HAIDARY
ABU TAHERA CHOWDHORY MOW
NOUSHAD HASAN JABIN

2. WELCOME
To Our
Presentation

3. Topic
Congestion Control

4. What is Congestion?
 Too much traffic on subnet cause congestion.
 It occur when subnet is out of buffer.
 Congestion On route.
 Queue overflows
 Packets droped
 Network congested.

5. Facts that Cause
Congestion?
 Insufficient memory.
 Slow Processor.
 Packet arrival rate.
 Low Bandwidth line also cause congestion.
 The main cause of congestion is bursty nature of traffic.

6. Congestion Control
 To prevent the congestion we need some several principles or rules.
These are:
1. Load Sheding
2. Choke Packets
3. Traffic Shapping
4. Random Early Discard

7. Load shedding
 Simple method
 drop packets
 Concept from electric power generation.
 Buffer full router discard packets.
 throw away packets.
 depends on application for discarded.

8. Wine Policy
Example: File transmission.
Milk Policy
Example: Live Streaming.

9. Choke Packets
 Congested router generate choke packets
 Transmit them
 Upon receiving sender reduce transmission rate

10. Choke Packets
Choke
Packet
Source Congested
Router

11. Choke Packets
A D
E
F
A
A
E
E
D
D
F

12. Explicit Congestion Notification
 Congested router mark packets
 Forward to destination
 Destination send Congestion Signal to Source
 Source slow down

13. Hop By Hop Choke Packets
 Choke packet effect all hops
 Reduce congestion instantly
 More effective than Choke Packets over long distance

14. Hop By Hop Choke Packets
A D
FE
FE
A
D
DA
E F
A
E F
D

15. Random Early Detection
 Doesn’t wait for queue to be completely fill up
 Maintain an Average length of queue
 Average length exceeds, discard few packets
 Lost packets works as choke packets
 Sender notice them and slow down

16. Traffic Shaping
Regulating the average rate and burstiness
Of a flow of data that enters the network.
Two traffic shaping algorithm are-
#1: Leaky Bucket
#2: Token Bucket

17. Leaky
Bucket
Shapes bursty traffic
into fixed-rate traffic by
averaging the data
rate.
Drop the packet if the
bucket is full.
Does nothing when
input is idle.

18. Leaky bucket implementation

19. Token bucket
The token bucket allows bursty traffic at a
regulated maximum rate.
-bucket holds tokens.
-to transmit a packet, the host must
capture and destroy one token.
-tokens are generated by a clock at a
rate one token every T sec.

20. Token bucket

21. Thank You
Any Question?