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CONGESTION AVOIDANCECONGESTION AVOIDANCE

AND CONTROLAND CONTROL

ByBy

M.SUJITHAM.SUJITHA

(09J21D5509)(09J21D5509)

JOGINPALLY B.R. ENGINEERING COLLEGEJOGINPALLY B.R. ENGINEERING COLLEGE

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CONTENTSCONTENTS

INTRODUCTIONINTRODUCTION

CONGESTION AND ITS NETWORK PERFORMANCECONGESTION AND ITS NETWORK PERFORMANCE SYSTEM ARCHITECTURESYSTEM ARCHITECTURE

HARD WARE ARCHITECTUREHARD WARE ARCHITECTURE

PROTOCOL ARCHITECTUREPROTOCOL ARCHITECTURE

CONGESTION AVOIDANCECONGESTION AVOIDANCE

CONGESTION CONTROLCONGESTION CONTROL

ADVANTAGESADVANTAGES

DISADVANTAGESDISADVANTAGES

APPLICATIONSAPPLICATIONS

CONCLUSION AND FUTURE SCOPECONCLUSION AND FUTURE SCOPE

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INTRODUCTIONINTRODUCTION

Congestion in a network may occur if the number of theCongestion in a network may occur if the number of the

packets sent to the networkpackets sent to the network is greater than the capacity ofis greater than the capacity of

the network.the network.

The transmitting data consists of slots in the window of theThe transmitting data consists of slots in the window of the

sender and the sender can send packets only as long as freesender and the sender can send packets only as long as free

slots are available.slots are available.

The approaches can be generally classified as protective orThe approaches can be generally classified as protective or

expansive controls.expansive controls.

To avoid the occurrence of congestion in a network we useTo avoid the occurrence of congestion in a network we use

congestion avoidance and congestion control techniques.congestion avoidance and congestion control techniques.

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CONGESTIONCONGESTION

Congestion occurs in a packet switched networkCongestion occurs in a packet switched network

the number of the packets sent to the networkthe number of the packets sent to the network is greater than the capacityis greater than the capacity

of the networkof the network

Congestion may happen in any of the system which involves waitingCongestion may happen in any of the system which involves waiting

congestion happens on a free way because any abnormality in the flow,congestion happens on a free way because any abnormality in the flow,

such as an accident during rush hour, creates blockage.such as an accident during rush hour, creates blockage.

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NETWORK PERFORMANCENETWORK PERFORMANCE

Congestion control involves two factors that measure the performance of network:Congestion control involves two factors that measure the performance of network:DelayDelay

ThroughputThroughput

DELAY VERSUS LOADDELAY VERSUS LOAD::

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THROUGHPUT VERSUS LOAD:THROUGHPUT VERSUS LOAD:

Throughput is defined as the number of the bits passing through a

point in a second. We can extend that definition from bits to packets

and from point to a network.

We can define the throughput in a network as the number of packets

passing through the network in a unit of time

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SYSTEM ARCHITECTURESYSTEM ARCHITECTURE

HARDWARE ARCHITECTUREHARDWARE ARCHITECTURE

The hardware architecture of an active network node will need to

provide substantial processing capabilities and easy access between

processing functions and node inputs and outputs.

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PROTOCOL ARCHITECTUREPROTOCOL ARCHITECTURE

The active processing control information may depend on multiple

protocol layers. For example, the APCI might include labels that

correspond to a block number in a file, a TCP sequence number, and an IP

datagram identifier.

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CONGESTION AVOIDANCECONGESTION AVOIDANCE

Mean+variance retransmit timeMean+variance retransmit time::

The congestion can be avoided in this using 2 methods:

Network must send a signal to the end points that congestion is about to occur.

At the end points there is a policy whether the signal is received or not.

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SLOW STARTSLOW START

Startup behavior of TCP without SlowStartup behavior of TCP without Slow--startstart

Maximum of the bandwidth is wasted in this strategy.

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Startup behavior of TCP with SlowStartup behavior of TCP with Slow--startstart

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ADDITIVE INCREASE & MULTIPLICATIVEADDITIVE INCREASE & MULTIPLICATIVE

DECREASEDECREASE

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CONGESTION CONTROLCONGESTION CONTROL

OPEN LOOP CONGESTION CONTROL:OPEN LOOP CONGESTION CONTROL:

RETRANSMISSION POLICYRETRANSMISSION POLICY

WINDOW POLICYWINDOW POLICY

ACKNOWLEDGEMENT POLICYACKNOWLEDGEMENT POLICY

DISCARDING POLICYDISCARDING POLICY ADMISSION POLICYADMISSION POLICY

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CLOSED LOOP CONGESTION CONTROL:CLOSED LOOP CONGESTION CONTROL:

BACK PRESSUREBACK PRESSURE

CHOKE POINTCHOKE POINT

IMPLICIT SIGNALINGIMPLICIT SIGNALING

EXPLICIT SIGNALLINGEXPLICIT SIGNALLING

BACKWARD SIGNALLINGBACKWARD SIGNALLING FORWARD SIGNALLINGFORWARD SIGNALLING

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USING AVOIDANCE TEST SET UPUSING AVOIDANCE TEST SET UP

WITH NO CONGESTION AVOIDANCEWITH NO CONGESTION AVOIDANCE

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WITH CONGESTION AVOIDANCEWITH CONGESTION AVOIDANCE

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ADVANTAGES:ADVANTAGES:

Lower pollution levelsLower pollution levels

Ease traffic flows i.e. reduced trafficEase traffic flows i.e. reduced traffic

Convenient and flexible for vehiclesConvenient and flexible for vehicles

Cheap and scalableCheap and scalable

Ease delivery / service vehicle access to premisesEase delivery / service vehicle access to premises

DISADVANTAGES:DISADVANTAGES:

Poor internet connectionsPoor internet connections

Requires cooperation of routersRequires cooperation of routers

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APPLICATIONSAPPLICATIONS

Large scale data transfersLarge scale data transfers

Real time streamingReal time streaming

MultimediaMultimedia

Video chatVideo chat Mobile networksMobile networks

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CONCLUSIONCONCLUSION

Finally we can conclude that the congestion in a network can beFinally we can conclude that the congestion in a network can beavoided by reducing the rate of dropping of packets andavoided by reducing the rate of dropping of packets and

increasing the size of bandwidth. And if both the strategies areincreasing the size of bandwidth. And if both the strategies are

controlled, the speed in a network can be increased to a highercontrolled, the speed in a network can be increased to a higher

rates.rates.

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REFERENCESREFERENCES

JACOBSON, V. Congestion avoidance and control. In Proceedings ofJACOBSON, V. Congestion avoidance and control. In Proceedings of

SIGCOMM 88(Stanford, CA, Aug. 1988), ACM.SIGCOMM 88(Stanford, CA, Aug. 1988), ACM.

JAIN, R. A timeoutJAIN, R. A timeout--based congestion control scheme for window flowbased congestion control scheme for window flow--

controlled Networks. IEEE Journal on Selected Areas in Communicationscontrolled Networks. IEEE Journal on Selected Areas in Communications

SACSAC--4, 7 (Oct. 1986).4, 7 (Oct. 1986).

JAIN, R., RAMAKRISHNAN, K., AND CHIU, D.JAIN, R., RAMAKRISHNAN, K., AND CHIU, D.--M. CongestionM. Congestion

avoidance in computer networks with a connectionless network layer.avoidance in computer networks with a connectionless network layer.

Tech. Rep. DECTech. Rep. DEC--TRTR--506, Digital Equipment Corporation, Aug. 1987506, Digital Equipment Corporation, Aug. 1987

NAGLE, J. Congestion Control in IP/TCP Internet works. ARPANETNAGLE, J. Congestion Control in IP/TCP Internet works. ARPANET

Working Group Requests for Comment, DDN Network InformationWorking Group Requests for Comment, DDN Network Information

Center, SRI International, Menlo Park, CA, Jan. 1984. RFCCenter, SRI International, Menlo Park, CA, Jan. 1984. RFC--896.896.

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THANK YOUTHANK YOU