Post on 09-Apr-2018
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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