Congestion and its control in networks

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By: saitwaln (51 month(s) ago)

very good seminar presention

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Slide 1: 

A SEMINAR ON CONGESTION CONTROL Prepared By:- Sukhdeep Singh Dhaliwal Barnala (Punjab)

TOPICS : 

TOPICS WHAT IS CONGESTION CAUSES OF CONGESTION GENERAL PRINCIPLES TO CONTROL CONGESTION A FEW ALGORITHMS FOR CONGESTION CONTROL

Data Transfer Terms : 

Data Transfer Terms Average Data Rate Peak Data Rate Maximum Burst Size Effective Bandwidth [ Traffic Profiles: Constant Bit Rate (CBR) Variable Bit Rate Bursty ) ]

WHAT IS CONGESTION : 

WHAT IS CONGESTION When too many packets are present in a network , the performance of the network, in terms of total throughput, average queued delay per packet, no. of packets lost, etc degrades. This situation is called congestion.

Slide 5: 

Network performance Delay versus Load

Slide 6: 

Throughput versus Load the reason is the discarding of packets by the routers

The congestion, and effect : 

The congestion, and effect Packets sent Packets Delivered Congested Desirable Perfect Maximum carrying capacity Of subnet

CAUSES OF CONGESTION : 

CAUSES OF CONGESTION Increase in packet transfer traffic Insufficient or infinite memory Slow processor Low bandwidth lines Mismatch between parts of the system

Motivation: History : 

Motivation: History Explosive growth in networks  congestion problems Oct 1986: Internet has series of “congestion collapses” “Collapse” = increment in offered load causes decrement in performance Throughput down by 1000 (32 kb/s to 40 b/s)

Congestion & Infinite Storage : 

Congestion & Infinite Storage PROBLEM OF TIMEOUT AND DUPLICATION

Congestion Control & Avoidance : 

Congestion Control & Avoidance Possible solutions :Three Categories Cooperative Solution Authoritarian Solution Market Solution

GENERAL PRINCIPLES OF CONGESTION CONTROL : 

GENERAL PRINCIPLES OF CONGESTION CONTROL Two types (by Yang and Reddy(1995)) :- Open Loop and Closed Loop {2 Types: implicit :congestion knowledge by local observations explicit : congestion knowledge by feedback }

Open loop : 

Open loop Solve problem by good design and deciding when to accept new traffic and when to discard packets and which ones.

Open loop : 

Open loop Various algorithms: Retransmission Policy Window Policy Discarding Policy Admission Policy

Slide 16: 

Open-loop congestion control Retransmission policy The retransmission policy and the retransmission timers must be designed to optimize efficiency and at the same time prevent congestion Acknowledgment policy If the receiver does not acknowledge every packet it receives, it may slow down the sender and help prevent congestion

Open-loop congestion control : 

Open-loop congestion control Discard policy In audio transmission, if the policy is to discard less sensitive packets when congestion is likely, the quality of sound is still preserved and congestion is prevented Window Policy Selective repeat policy is better than Go-Back-N window for congestion

Closed loop : 

Closed loop Based on concept of feedback, has three parts when applied: Monitor the system to detect when and where congestion occurs. Pass information to the places where actions can be taken. Adjust system operation to correct the problem.

Closed loop : 

Closed loop Various algorithms: Back Pressure Choke Packet Implicit Signaling Explicit Signaling Leaky Bucket

Back Pressure : 

Back Pressure Data Flow Back pressure Source Destination

Choke Packet : 

Choke Packet Choke Bit Data Flow Source Destination

Implicit Signaling : 

Implicit Signaling And communication between congested and the source.

Explicit Signaling : 

Explicit Signaling Congested node can explicitly send signal to the source or destination 2 Types: Backward Signaling Forward Signaling

Leaky Bucket Algorithm : 

Leaky Bucket Algorithm Fundamental concept of leaky bucket algorithm Tap Bucket Leak Hole Given By:TURNER(1986)

Leaky Bucket Algorithm : 

Leaky Bucket Algorithm AN INTERFACE BETWEEN HOST AND NETWORK Packet With Irregular Flow Regulated Flow 4 Packets Per Second NETWORK

Slide 26: 

Token Bucket(burst output for input) Host Computer Packet Interface Token

Thank You All : 

Thank You All