This document presents an overview of computer network congestion and congestion control techniques. It defines congestion as occurring when too many packets are present in a network link, causing queues to overflow and packets to drop. It then discusses factors that can cause congestion as well as the costs. It outlines open-loop and closed-loop congestion control approaches. Specific algorithms covered include leaky bucket, token bucket, choke packets, hop-by-hop choke packets, and load shedding. The document concludes by noting the importance of efficient congestion control techniques with room for improvement.
The network layer is responsible for routing packets from the source to destination. The routing algorithm is the piece of software that decides where a packet goes next (e.g., which output line, or which node on a broadcast channel).For connectionless networks, the routing decision is made for each datagram. For connection-oriented networks, the decision is made once, at circuit setup time.
Routing Issues
The routing algorithm must deal with the following issues:
Correctness and simplicity: networks are never taken down; individual parts (e.g., links, routers) may fail, but the whole network should not.
Stability: if a link or router fails, how much time elapses before the remaining routers recognize the topology change? (Some never do..)
Fairness and optimality: an inherently intractable problem. Definition of optimality usually doesn't consider fairness. Do we want to maximize channel usage? Minimize average delay?
When we look at routing in detail, we'll consider both adaptive--those that take current traffic and topology into consideration--and nonadaptive algorithms.
The Network Layer is concerned about getting packets from source to destination, no matter how many hops it may take. It’s all about routing.
5.1 Network Layer Design Issues
What do we need to think about in this layer?
5.2 Routing Algorithms
Strategies for getting from source to destination.
5.3 Congestion Control Algorithms
How do we keep from bottlenecking from too many packets?
5.4 Internetworking
Working with multiple networks and protocols in order to deliver packets.
5.5 The Network Layer in the Internet
Gluing together a collection of subnets.
The network layer is responsible for routing packets from the source to destination. The routing algorithm is the piece of software that decides where a packet goes next (e.g., which output line, or which node on a broadcast channel).For connectionless networks, the routing decision is made for each datagram. For connection-oriented networks, the decision is made once, at circuit setup time.
Routing Issues
The routing algorithm must deal with the following issues:
Correctness and simplicity: networks are never taken down; individual parts (e.g., links, routers) may fail, but the whole network should not.
Stability: if a link or router fails, how much time elapses before the remaining routers recognize the topology change? (Some never do..)
Fairness and optimality: an inherently intractable problem. Definition of optimality usually doesn't consider fairness. Do we want to maximize channel usage? Minimize average delay?
When we look at routing in detail, we'll consider both adaptive--those that take current traffic and topology into consideration--and nonadaptive algorithms.
The Network Layer is concerned about getting packets from source to destination, no matter how many hops it may take. It’s all about routing.
5.1 Network Layer Design Issues
What do we need to think about in this layer?
5.2 Routing Algorithms
Strategies for getting from source to destination.
5.3 Congestion Control Algorithms
How do we keep from bottlenecking from too many packets?
5.4 Internetworking
Working with multiple networks and protocols in order to deliver packets.
5.5 The Network Layer in the Internet
Gluing together a collection of subnets.
Hello People.. Welcome to GURUKULA!!!
Have you ever thought that how the protocols that are required for the effective delivery of the messages from one place to anpther place take place in a real time internet..... This video explains about the concept called PROTOCOL LAYERING, where you can learn the way how the protocols are layered in such a way..
Simple examples are also used to make the concepts clean nd clear.
This video will help you to learn:
What is protocol layering in networks, OSI Model in Computer Networks, Layers of OSI Model, OSI Model, OSI Internet Module, OSI Layers and their Functions, Examples of OSI Models, 7 layers of OSI Models, Principles of Protocol Layering, Why layering the Protocols,
Thanks for Watching, Keep Supporting and Keep Sharing...
Hello People.. Welcome to GURUKULA!!!
Have you ever thought that how the protocols that are required for the effective delivery of the messages from one place to anpther place take place in a real time internet..... This video explains about the concept called PROTOCOL LAYERING, where you can learn the way how the protocols are layered in such a way..
Simple examples are also used to make the concepts clean nd clear.
This video will help you to learn:
What is protocol layering in networks, OSI Model in Computer Networks, Layers of OSI Model, OSI Model, OSI Internet Module, OSI Layers and their Functions, Examples of OSI Models, 7 layers of OSI Models, Principles of Protocol Layering, Why layering the Protocols,
Thanks for Watching, Keep Supporting and Keep Sharing...
This presentation about Conjestion control will enrich your knowledge about this topic.and use this presentation for your reference this presentation with the Leaky bucket algorithm.
Packet losses at IP network are common behavior at
the time of congestion. The TCP traffic is explained as in
terms of load and capacity. The load should be measured as
number of sender actively competes for a bottleneck link and
the capacity as the total network buffering available to those
senders. Though there are many congestion mechanism
already in practice like congestion window, slow start,
congestion avoidance, fast transmit but still we see erratic
behavior when there is a large traffic. The TCP protocol that
controls sources send rates degrades rapidly if the network
cannot store at least a few packets per active connection. Thus
the amount of router buffer space required for good
performance scales with the number of active connections
and the bandwidth utilization by each active connections. As
in the current practice, the buffer space does not scale in this
way and router drops the packet without looking at bandwidth
utilization of each connections. The result is global
synchronization and phase effect as well as packet from the
unlucky sender will be frequently dropped. The simultaneous
requirements of low queuing delay and of large buffer
memories for large numbers of connections pose a problem.
Routers should enforce a dropping policy by proportional to
the bandwidth utilization by each active connection. Router
will provision the buffering mechanism when processing slows
down. This study explains the existing problem with drop-tail
and RED routers and proposes the new mechanism to predict
the effective bandwidth utilization of the clients depending
on their history of utilization and drop the packet in different
pattern after analyzing the network bandwidth utilization at
each specific interval of time
A state occurring in network layer when the message traffic is so heavy that it slows down network response time.
Effects of Congestion
As delay increases, performance decreases.
If delay increases, retransmission occurs, making situation worse.
What is congestion?
A state occurring in network layer when the message traffic is so heavy that it slows down network response time.
Effects of Congestion
As delay increases, performance decreases.
If delay increases, retransmission occurs, making situation worse.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
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UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
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Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
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See how to accelerate model training and optimize model performance with active learning
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👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
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During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
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- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
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Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
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Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
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https://www.rttsweb.com/jmeter-integration-webinar
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Generating a custom Ruby SDK for your web service or Rails API using Smithyg2nightmarescribd
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UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
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1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
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Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
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Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
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Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
2. CONTENTS
INTRODUCTIONTO CONGESTION
GENERAL PRINCIPLE OF CONGESTION
OPEN LOOP CONGESTION CONTRO
CLOSED LOOP CONGESTION CONTROL
CONGESTION CONTROL ALGORITHMS
LEAKY BUCKETALGORITHM
TOKEN BUCKET ALGORITHM
CHOKE PACKETS
HOP BY HOP CHOKE PACKETS
LOAD SHEDDING
CONCLUSION
REFERENCE
2
3. INTRODUCTION
WHAT IS CONGESTION?
Congestion is a situation in communication network in which
too many packets are present in a part of the subnet or
contending for the same link so
The queue overflows
Packets get dropped
Network is congested!
3
ROUTER
BUFFER
BUFFER
BUFFER
BUFFER
BUFFER
CONGESTION
4. Factors that Cause Congestion
Packet arrival rate exceeds the outgoing link capacity.
Insufficient memory to store arriving packets
Bursty traffic
Slow processor
Costs of congestion
large queuing delays are experienced as the packet
arrival rate nears the link capacity.
unneeded retransmissions by the sender
when a packet is dropped along a path, the
transmission capacity of the upstream routers have
been wasted.
4
5. GENERAL PRINCIPLE OF CONGESTION CONTROL
Congestion control refers to techniques and mechanisms that can either
prevent congestion , before it happens or removes congestion,after it has
happened.
5
CONGESTION
CONTROL
OPEN LOOP
RETRANSMISSION
POLICY
WINDOW
POLICY
ACKNOWLEDGEMENT
POLICY
DISCARDING
POLICY
ADMISSION
POLICY
CLOSED
LOOP
BACK
PRESSURE
CHOKE
PACKET
IMPLICIT
SIGNALING
EXPLICIT
SIGNALING
6. •In this method, policies are used to prevent the congestion before
it happens.
Congestion control is handled either by the source or by the
destination.
1. Retransmission Policy
•The sender retransmits a packet, if it feels that the packet it
has sent is lost or corrupted.
•The retransmission policy and the retransmission timers need
to be designed to optimize efficiency and at the same time
prevent the congestion.
2. Window Policy
•To implement window policy, selective reject window method
is used for congestion control in which it sends only the specific
lost or damaged packets.
6
Open loop congestion control
7. 3. Acknowledgement Policy
• If the receiver does not acknowledge every packet it receives it
may slow down the sender and help prevent congestion.
4. Discarding Policy
• A router may discard less sensitive packets when congestion is
likely to happen
5. Admission Policy
• A router can deny establishing a virtual circuit connection if
there is congestion in the "network or if there is a possibility of
future congestion.
6. Routing Algorithm
• spreading the traffic over all the lines
7
8. 8
Congestion prevention policies in different layers
LAYER CONGESTION PREVENTION POLICIES
Transport -retransmission policy
-acknowledgement policy
-flow control policy
-timeout determination
Network -virtual circuits versus datagram inside the subnet
-packet queuing and service policy
-packet discard policy
-routing algorithm
-packet lifetime management
Datalink -retransmission policy
-out-of-order caching policy
-acknowledgement policy
-flow control policy
9. CLOSED LOOP CONGESTION CONTROL
• Closed loop congestion control mechanisms try to remove the
congestion after it happens.
1. Backpressure method
• Backpressure is a node-to-node congestion control that starts with a
node and propagates, in the opposite direction of data flow in which
the congested node stops receiving data from the immediate
upstream node(s).
9
Source 1 2 3 4 destination
congestion
Back pressure
DownstreamUpstream
Data flow
10. 2. Choke Packet
• In choke packet method, congested node sends a
warning directly to the source station i.e. the
intermediate nodes through which the packet
has traveled are not warned.
10
Source 1 2 3 4 Destination
Choke packet
congestion
Data flow
11. 3. Implicit Signaling
•The source guesses that there is congestion somewhere in
the network when it does not receive any acknowledgment.
Therefore the delay in receiving an acknowledgment is
interpreted as congestion in the network and the source
slows down.
- this policy is used inTCP(Transmission control protocol).
4. Explicit Signaling
• In this method, the congested nodes explicitly send a
signal to the source or destination to inform about the
congestion.
• Explicit signaling is different from the choke packet
method. In choke packed method, a separate packet is used
for this purpose whereas in explicit signaling method, the
signal is included in the packets that carry data .
11
14. Choke Packet Technique
Depicts the functioning of choke packets, (a) Heavy traffic
between nodes P and Q, (b) Node Q sends the Choke packet to P,
(c) Choke packet reaches P, (d) P reduces the flow and send a
reduced flow out, (e) Reduced flow reaches node Q .
14
15. Hop-by Hop Choke Packets
15
Depicts the functioning of Hop-by-Hop choke packets (a) Heavy traffic
between nodes P and Q, (b) Node Q sends the Choke packet to P, (c) Choke packet
reaches R, and the flow between R and Q is curtail down, Choke packer reaches P,
and P reduces the flow out .
16. Load Shedding
- In this method, whenever a router finds that there is congestion
in the network, it simply starts dropping out the packets.
- Which packet to discard depends on the applications running
-Wine policy: the older the better.
-Milk policy: fresher is better
-intelligent discard policy:packets in priority classes
16
17. conclusion
17
With the increase in the number of internet
users, it has become quite essential to
develop an efficient congestion control
technique.
In our presentation we have analyse Leaky
bucket algorithm,Token bucket algorithm,
Choked packet technique and Hop by hop
choke packet technique.
A particular algorithm cannot be hundred
percent efficient, so there is always scope to
improve the congestion control technique.
18. Reference
Computer control overview written by S. Chen
“What is Congestion Control Describe the
Congestion Control Algorithm commonly used.”
written by DineshThakur.
Computer Network:A system aproach,5E by Larry
L. Peterson & Bruce S. Davie
[Ramakrishnan 1990] K. K. Ramakrishnan and Raj
Jain, "A Binary Feedback Scheme for Congestion
Avoidance in Computer Networks", ACM
Transactions on Computer Systems,Vol.8, No.2, pp.
158-181, May 1990.
18