DCTcp
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DCTCP is an enhancement to TCP for data center networks that leverages ECN to provide more granular congestion feedback than standard TCP. It estimates the fraction of marked packets to react to the extent of congestion rather than just its presence. This finer control allows DCTCP to maintain low buffer occupancy while achieving high throughput. The algorithm adapts the window size based on the marked packet ratio in each RTT to be more responsive to congestion than standard TCP. DCTCP addresses the key requirements for data center networks of handling bursty traffic, low latency, and high throughput.
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This document discusses data center networking. It covers key characteristics like low latencies measured in microseconds, high capacity networks using Gigabit and 10 Gigabit Ethernet, and specialized traffic patterns. It also discusses common problems in data center networks like incast where a single server receives requests from many servers simultaneously, overwhelming its network capacity. Recent research proposals to address these issues include new switching topologies, adjusting TCP for incast, and the Data Center TCP protocol to provide low latency for short flows, high burst tolerance, and high throughput for long flows. Data center networks require specialized solutions due to their unique characteristics compared to wide area networks.
TCP-FIT: An Improved TCP Congestion Control Algorithm and its Performance
The document discusses TCP-FIT, a new TCP congestion control algorithm inspired by parallel TCP. TCP-FIT aims to improve TCP performance in scenarios with high bandwidth-delay products (BDP) or wireless networks. It classifies congestion control algorithms and discusses their limitations. TCP-FIT adapts concepts from parallel TCP like GridFTP to achieve high utilization while maintaining compatibility and fairness. Experimental results show TCP-FIT performs well in BDP and wireless scenarios and achieves inter-fairness and RTT-fairness. However, its bandwidth estimation model is simplistic compared to FAST TCP, resulting in lower performance on networks with large bandwidth variations.
Congestion control avoidance
Computer networks have experienced an explosive growth over the past few years and with
that growth have come severe congestion problems. For example, it is now common to see
internet gateways drop 10% of the incoming packets because of local buffer overflows.
Our investigation of some of these problems has shown that much of the cause lies in
transport protocol implementations (
not
in the protocols themselves): The ‘obvious’ ways
to implement a window-based transport protocol can result in exactly the wrong behavior
in response to network congestion. We give examples of ‘wrong’ behavior and describe
some simple algorithms that can be used to make right things happen. The algorithms are
rooted in the idea of achieving network stability by forcing the transport connection to obey
a ‘packet conservation’ principle. We show how the algorithms derive from this principle
and what effect they have on traffic over congested networks.
In October of ’86, the Internet had the first of what became a series of ‘congestion col-
lapses’. During this period, the data throughput from LBL to UC Berkeley (sites separated
by 400 yards and two IMP hops) dropped from 32 Kbps to 40 bps. We were fascinated by
this sudden factor-of-thousand drop in bandwidth and embarked on an investigation of why
things had gotten so bad. In particular, we wondered if the 4.3
BSD
(Berkeley U
NIX
)
TCP
was mis-behaving or if it could be tuned to work better under abysmal network conditions.
The answer to both of these questions was “yes”.
Congestion control in tcp
This document summarizes a presentation on congestion control in TCP/IP networks. It discusses basics of congestion and how it can be catastrophic if not handled. It then describes the basic strategies used by TCP to combat congestion, including slow start, congestion avoidance, detection, and illustration of algorithms like fast retransmit and recovery. Issues with wireless networks and variants of TCP like New Reno, Vegas, and Westwood are also summarized. The presentation proposes a new congestion control algorithm and discusses plans to simulate and test it.
Cubic
CUBIC is a TCP congestion control algorithm that uses a cubic window growth function to help TCP scale better in high bandwidth-delay product networks. It aims to improve scalability, stability, and fairness compared to previous algorithms like BIC-TCP. The window growth is independent of round-trip time and becomes nearly zero around the maximum window size to help stability. CUBIC also incorporates features to help it behave friendly to standard TCP implementations.
TCP Congestion Control
Transmission Control Protocol (TCP) is a fundamental protocol of the Internet Protocol Suite. TCP complements the Internet Protocol (IP), therefore it is common to refer to the internet protocol suit as TCP/IP. TCP is used for error detection, detection of packet loss or out of order delivery of data. TCP requests retransmission, rearranges data and helps with network congestion.
Several congestion control algorithms have been developed, over the last years, to improve TCP's performance over various technologies and network conditions.
The purpose of this assignment is to present TCP, network congestion, congestion algorithms and simulate different algorithms in different network conditions to measure their performance. For this assignment's needs, OPNET IT Guru Academic Edition software was used to accomplish the reproduction of projects that have been already published and gave the wanted results.
Tcp congestion avoidance algorithm identification
The document describes a tool called TCP Congestion Avoidance Algorithm Identification (CAAI) that was proposed to identify the TCP congestion avoidance algorithm of remote web servers. CAAI works in three steps: 1) it gathers TCP window size traces from web servers in emulated network environments, 2) it extracts features like the multiplicative decrease parameter and window growth function from the traces, and 3) it uses these features to classify the TCP algorithm. Testing CAAI on over 30,000 web servers, it was able to identify the default algorithms used by major operating systems, like RENO for Windows and BIC/CUBIC for Linux, as well as some non-default algorithms.
Tcp congestion control
The document discusses TCP congestion control algorithms. It describes the Additive Increase Multiplicative Decrease (AIMD) approach where the congestion window (cwnd) is increased linearly but reduced by half when packet loss is detected. Slow start is used to quickly ramp up cwnd initially through exponential growth. Fast retransmit detects lost packets using duplicate ACKs to retransmit earlier. Fast recovery then resumes increasing cwnd after a retransmit. The document also examines algorithms for adaptive retransmission timeouts based on mean and variance of measured round-trip times.
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This document discusses data center networking. It covers key characteristics like low latencies measured in microseconds, high capacity networks using Gigabit and 10 Gigabit Ethernet, and specialized traffic patterns. It also discusses common problems in data center networks like incast where a single server receives requests from many servers simultaneously, overwhelming its network capacity. Recent research proposals to address these issues include new switching topologies, adjusting TCP for incast, and the Data Center TCP protocol to provide low latency for short flows, high burst tolerance, and high throughput for long flows. Data center networks require specialized solutions due to their unique characteristics compared to wide area networks.
TCP-FIT: An Improved TCP Congestion Control Algorithm and its Performance
The document discusses TCP-FIT, a new TCP congestion control algorithm inspired by parallel TCP. TCP-FIT aims to improve TCP performance in scenarios with high bandwidth-delay products (BDP) or wireless networks. It classifies congestion control algorithms and discusses their limitations. TCP-FIT adapts concepts from parallel TCP like GridFTP to achieve high utilization while maintaining compatibility and fairness. Experimental results show TCP-FIT performs well in BDP and wireless scenarios and achieves inter-fairness and RTT-fairness. However, its bandwidth estimation model is simplistic compared to FAST TCP, resulting in lower performance on networks with large bandwidth variations.
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Computer networks have experienced an explosive growth over the past few years and with
that growth have come severe congestion problems. For example, it is now common to see
internet gateways drop 10% of the incoming packets because of local buffer overflows.
Our investigation of some of these problems has shown that much of the cause lies in
transport protocol implementations (
not
in the protocols themselves): The ‘obvious’ ways
to implement a window-based transport protocol can result in exactly the wrong behavior
in response to network congestion. We give examples of ‘wrong’ behavior and describe
some simple algorithms that can be used to make right things happen. The algorithms are
rooted in the idea of achieving network stability by forcing the transport connection to obey
a ‘packet conservation’ principle. We show how the algorithms derive from this principle
and what effect they have on traffic over congested networks.
In October of ’86, the Internet had the first of what became a series of ‘congestion col-
lapses’. During this period, the data throughput from LBL to UC Berkeley (sites separated
by 400 yards and two IMP hops) dropped from 32 Kbps to 40 bps. We were fascinated by
this sudden factor-of-thousand drop in bandwidth and embarked on an investigation of why
things had gotten so bad. In particular, we wondered if the 4.3
BSD
(Berkeley U
NIX
)
TCP
was mis-behaving or if it could be tuned to work better under abysmal network conditions.
The answer to both of these questions was “yes”.
Congestion control in tcp
This document summarizes a presentation on congestion control in TCP/IP networks. It discusses basics of congestion and how it can be catastrophic if not handled. It then describes the basic strategies used by TCP to combat congestion, including slow start, congestion avoidance, detection, and illustration of algorithms like fast retransmit and recovery. Issues with wireless networks and variants of TCP like New Reno, Vegas, and Westwood are also summarized. The presentation proposes a new congestion control algorithm and discusses plans to simulate and test it.
Cubic
CUBIC is a TCP congestion control algorithm that uses a cubic window growth function to help TCP scale better in high bandwidth-delay product networks. It aims to improve scalability, stability, and fairness compared to previous algorithms like BIC-TCP. The window growth is independent of round-trip time and becomes nearly zero around the maximum window size to help stability. CUBIC also incorporates features to help it behave friendly to standard TCP implementations.
TCP Congestion Control
Transmission Control Protocol (TCP) is a fundamental protocol of the Internet Protocol Suite. TCP complements the Internet Protocol (IP), therefore it is common to refer to the internet protocol suit as TCP/IP. TCP is used for error detection, detection of packet loss or out of order delivery of data. TCP requests retransmission, rearranges data and helps with network congestion.
Several congestion control algorithms have been developed, over the last years, to improve TCP's performance over various technologies and network conditions.
The purpose of this assignment is to present TCP, network congestion, congestion algorithms and simulate different algorithms in different network conditions to measure their performance. For this assignment's needs, OPNET IT Guru Academic Edition software was used to accomplish the reproduction of projects that have been already published and gave the wanted results.
Tcp congestion avoidance algorithm identification
The document describes a tool called TCP Congestion Avoidance Algorithm Identification (CAAI) that was proposed to identify the TCP congestion avoidance algorithm of remote web servers. CAAI works in three steps: 1) it gathers TCP window size traces from web servers in emulated network environments, 2) it extracts features like the multiplicative decrease parameter and window growth function from the traces, and 3) it uses these features to classify the TCP algorithm. Testing CAAI on over 30,000 web servers, it was able to identify the default algorithms used by major operating systems, like RENO for Windows and BIC/CUBIC for Linux, as well as some non-default algorithms.
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¤ TCP Westwood is a congestion control algorithm that improves TCP performance over wireless networks by estimating available bandwidth (BWE) through monitoring ACK packets.
¤ It uses a low-pass filter to average bandwidth measurements and obtain the low-frequency components of available bandwidth. When inter-arrival times of ACKs increase, more weight is given to the most recent bandwidth calculations.
¤ TCP Westwood achieves better throughput than TCP Reno over lossy links and converges to a fair share of bandwidth when competing with other TCP variants like Reno.
Lect9
- TCP uses congestion control and avoidance to prevent network congestion collapse. It operates in a distributed manner without centralized control.
- TCP's congestion control is based on additive increase, multiplicative decrease (AIMD) and uses a congestion window and packet pacing to smoothly increase and decrease transmission rates in response to packet loss as a signal of congestion.
- The key mechanisms are slow start for initial rapid ramp up, congestion avoidance for gradual increase, fast retransmit for quick recovery from single losses, and timeout for recovery from multiple losses or ack losses. These mechanisms work together to keep TCP stable and efficient under different network conditions.
Tcp congestion avoidance
TCP provides reliable data transmission through mechanisms like the three-way handshake, congestion control using AIMD, and fast retransmit. However, it is vulnerable to attacks like RST injection to terminate connections or FIN scans to detect open ports. Defenses include randomizing sequence numbers, stateful firewalls to validate packets, and intrusion detection systems to detect scanning behaviors.
Adoptive flowcontrol in TCP
TCP sliding window provides reliable data delivery, ordered data delivery, and flow control between sender and receiver. It works by having the sender track the highest byte sent and acknowledged, and the receiver track the highest byte received and read. This allows each side to know how much buffer space is available. The receiver advertises its available window size to limit how much unacknowledged data the sender can have outstanding.
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TCP uses congestion control algorithms to dynamically adjust the transmission rate depending on network conditions. It uses three main algorithms:
1. Slow start exponentially increases the congestion window when no congestion is detected.
2. Congestion avoidance additively increases the window when congestion is detected to slow growth.
3. Fast recovery allows additive increases when duplicate ACKs are received, indicating a lost packet but not severe congestion.
TCP detects congestion through timeouts or duplicate ACKs and multiplicatively decreases the window size by half in response to avoid worsening congestion. It transitions between these algorithms depending on congestion signs to maximize throughput while avoiding network overload.
Analysis of TCP variants
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TCP congestion control
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This document summarizes key concepts about congestion control in TCP including:
- TCP uses additive increase multiplicative decrease (AIMD) to dynamically adjust the congestion window size and maintain efficiency and fairness.
- TCP has slow start and congestion avoidance states that govern how the congestion window is adjusted in response to acknowledgements.
- TCP responds to packet loss through fast retransmit, fast recovery, and halving the congestion window size to reduce congestion according to protocols like Tahoe, Reno, and New Reno.
Congestion Control in Computer Networks - ATM and TCP
This document discusses congestion control in networks using ATM and TCP protocols. It defines network congestion and outlines various congestion control possibilities including admission control, traffic access control, packet scheduling, buffer management, and flow control. It then describes the key concepts and congestion control mechanisms for ATM, including call admission control, the GCRA algorithm, and use of resource management cells. It also outlines TCP congestion control using additive increase/multiplicative decrease and slow start/fast retransmit, and evaluates the pros and cons of ATM and TCP approaches.
Congestion control
This document discusses various techniques for congestion control in computer networks. It describes:
1. The difference between congestion control, which deals with overall traffic levels across a network, and flow control, which regulates traffic between two endpoints.
2. Common congestion control techniques like leaky bucket and token bucket algorithms, which shape traffic to prevent bursts that could cause congestion.
3. Other approaches like choke packets, where routers notify sources to reduce their transmission rates if a link becomes congested, and load shedding as a last resort if congestion cannot be avoided.
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The document discusses several algorithms used for congestion control in TCP/IP networks, including slow start, congestion avoidance, fast retransmit, fast recovery, random early discard (RED), and traffic shaping using leaky bucket and token bucket algorithms. Slow start and congestion avoidance control the transmission rate by adjusting the congestion window size. Fast retransmit and fast recovery allow quicker retransmission of lost packets without waiting for timeouts. RED proactively discards packets before buffer overflow. Leaky bucket and token bucket algorithms shape traffic flow through use of buffers and tokens to smooth bursts and control transmission rates.
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While datacenters are increasingly adopting VMs to provide elastic cloud services, they still rely on traditional TCP for congestion control. In this talk, I will first show that VM scheduling delays can heavily contaminate RTTs sensed by VM senders, preventing TCP from correctly learning the physical network condition. Focusing on the incast problem, which is commonly seen in large-scale distributed data processing such as MapReduce and web search, I find that the solutions that have been developed for *physical* clusters fall short in a Xen *virtual* cluster. Second, I will provide a concrete understanding of the problem, and reveal that the situations that when the sending VM is preempted versus when the receiving VM is preempted, are different. Third, I will introduce my recent attempts on paravirtualizing TCP to overcome the negative effect caused by VM scheduling delays.Adoptive retransmission in TCP
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Mobile computing-tcp data flow control
This document discusses TCP data flow control and congestion control mechanisms for mobile networks. It describes how TCP uses windows, acknowledgements, and timeouts to regulate data transmission rates. Some key challenges with directly applying TCP to mobile networks are high packet loss rates leading to frequent window resizing and reduced throughput. The document proposes methods for mobile networks like split TCP, fast retransmit/recovery, and TCP-aware link layers to address these challenges.
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The document summarizes two algorithms for regulating network traffic:
1. The Leaky Bucket Algorithm models traffic as water entering a bucket with a hole, limiting output to a constant rate regardless of input rate. Packets are discarded if the bucket is full.
2. The Token Bucket Algorithm generates tokens periodically that must be removed from the bucket before packets can be transmitted, allowing bursts up to the token capacity. This is less restrictive than the Leaky Bucket Algorithm.
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Lect9 (1)
TCP uses congestion control to prevent network congestion collapse. It uses additive increase multiplicative decrease (AIMD) where the sending rate is increased slowly but cut in half after a loss. TCP paces packets using a congestion window that limits unacknowledged data. It uses slow start to quickly reach bandwidth and congestion avoidance to increase the window by 1 packet per RTT. This models TCP behavior and shows throughput is related to window size, loss rate, and RTT.
Congestion control in TCP
TCP uses congestion control to determine how much capacity is available in the network and regulate how many packets can be in transit. It uses additive increase/multiplicative decrease (AIMD) where the congestion window is increased slowly with each ACK but halved upon timeout. Slow start is used initially and after idle periods to grow the window exponentially until congestion is detected. Fast retransmit and fast recovery help detect and recover from packet loss without requiring a timeout.
3a data link layer continued
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Improving Distributed TCP Caching for Wireless Sensor Networks
The document proposes an enhanced distributed TCP caching (EDTC) approach to improve TCP performance over wireless sensor networks. EDTC improves upon distributed TCP caching (DTC) by detecting and handling TCP acknowledgment losses, disabling unnecessary retransmissions, and using a smoothed retransmission timeout value. Simulation results show that EDTC reduces energy consumption and transfer duration compared to DTC and TCP, especially in high packet loss networks.
Performance Evaluation of High Speed Congestion Control Protocols
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¤ TCP Westwood is a congestion control algorithm that improves TCP performance over wireless networks by estimating available bandwidth (BWE) through monitoring ACK packets.
¤ It uses a low-pass filter to average bandwidth measurements and obtain the low-frequency components of available bandwidth. When inter-arrival times of ACKs increase, more weight is given to the most recent bandwidth calculations.
¤ TCP Westwood achieves better throughput than TCP Reno over lossy links and converges to a fair share of bandwidth when competing with other TCP variants like Reno.
Lect9
- TCP uses congestion control and avoidance to prevent network congestion collapse. It operates in a distributed manner without centralized control.
- TCP's congestion control is based on additive increase, multiplicative decrease (AIMD) and uses a congestion window and packet pacing to smoothly increase and decrease transmission rates in response to packet loss as a signal of congestion.
- The key mechanisms are slow start for initial rapid ramp up, congestion avoidance for gradual increase, fast retransmit for quick recovery from single losses, and timeout for recovery from multiple losses or ack losses. These mechanisms work together to keep TCP stable and efficient under different network conditions.
Tcp congestion avoidance
TCP provides reliable data transmission through mechanisms like the three-way handshake, congestion control using AIMD, and fast retransmit. However, it is vulnerable to attacks like RST injection to terminate connections or FIN scans to detect open ports. Defenses include randomizing sequence numbers, stateful firewalls to validate packets, and intrusion detection systems to detect scanning behaviors.
Adoptive flowcontrol in TCP
TCP sliding window provides reliable data delivery, ordered data delivery, and flow control between sender and receiver. It works by having the sender track the highest byte sent and acknowledged, and the receiver track the highest byte received and read. This allows each side to know how much buffer space is available. The receiver advertises its available window size to limit how much unacknowledged data the sender can have outstanding.
TCP Congestion Control By Owais Jara
TCP uses congestion control algorithms to dynamically adjust the transmission rate depending on network conditions. It uses three main algorithms:
1. Slow start exponentially increases the congestion window when no congestion is detected.
2. Congestion avoidance additively increases the window when congestion is detected to slow growth.
3. Fast recovery allows additive increases when duplicate ACKs are received, indicating a lost packet but not severe congestion.
TCP detects congestion through timeouts or duplicate ACKs and multiplicatively decreases the window size by half in response to avoid worsening congestion. It transitions between these algorithms depending on congestion signs to maximize throughput while avoiding network overload.
Analysis of TCP variants
This document discusses several TCP congestion control algorithms: TCP Tahoe, Reno, New Reno, SACK, and Vegas. It provides details on how each algorithm handles slow start, congestion avoidance, fast retransmit, and congestion detection. TCP Vegas is highlighted as being superior to the other algorithms because it can detect and retransmit lost packets faster, has fewer retransmissions, more efficiently measures bandwidth availability, and experiences less congestion overall through proactive congestion detection and modified slow start and congestion avoidance.
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This document provides an overview of TCP congestion control algorithms. It describes the basic additive increase/multiplicative decrease approach and key mechanisms like slow start, fast retransmit, and fast recovery. It also discusses algorithms for setting the retransmission timeout value and adaptations made in protocols like New Reno and Cubic.
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This document summarizes key concepts about congestion control in TCP including:
- TCP uses additive increase multiplicative decrease (AIMD) to dynamically adjust the congestion window size and maintain efficiency and fairness.
- TCP has slow start and congestion avoidance states that govern how the congestion window is adjusted in response to acknowledgements.
- TCP responds to packet loss through fast retransmit, fast recovery, and halving the congestion window size to reduce congestion according to protocols like Tahoe, Reno, and New Reno.
Congestion Control in Computer Networks - ATM and TCP
This document discusses congestion control in networks using ATM and TCP protocols. It defines network congestion and outlines various congestion control possibilities including admission control, traffic access control, packet scheduling, buffer management, and flow control. It then describes the key concepts and congestion control mechanisms for ATM, including call admission control, the GCRA algorithm, and use of resource management cells. It also outlines TCP congestion control using additive increase/multiplicative decrease and slow start/fast retransmit, and evaluates the pros and cons of ATM and TCP approaches.
Congestion control
This document discusses various techniques for congestion control in computer networks. It describes:
1. The difference between congestion control, which deals with overall traffic levels across a network, and flow control, which regulates traffic between two endpoints.
2. Common congestion control techniques like leaky bucket and token bucket algorithms, which shape traffic to prevent bursts that could cause congestion.
3. Other approaches like choke packets, where routers notify sources to reduce their transmission rates if a link becomes congested, and load shedding as a last resort if congestion cannot be avoided.
Tcp Congestion Avoidance
The document discusses several algorithms used for congestion control in TCP/IP networks, including slow start, congestion avoidance, fast retransmit, fast recovery, random early discard (RED), and traffic shaping using leaky bucket and token bucket algorithms. Slow start and congestion avoidance control the transmission rate by adjusting the congestion window size. Fast retransmit and fast recovery allow quicker retransmission of lost packets without waiting for timeouts. RED proactively discards packets before buffer overflow. Leaky bucket and token bucket algorithms shape traffic flow through use of buffers and tokens to smooth bursts and control transmission rates.
XPDS13: On Paravirualizing TCP - Congestion Control on Xen VMs - Luwei Cheng,...
XPDS13: On Paravirualizing TCP - Congestion Control on Xen VMs - Luwei Cheng,...The Linux Foundation
While datacenters are increasingly adopting VMs to provide elastic cloud services, they still rely on traditional TCP for congestion control. In this talk, I will first show that VM scheduling delays can heavily contaminate RTTs sensed by VM senders, preventing TCP from correctly learning the physical network condition. Focusing on the incast problem, which is commonly seen in large-scale distributed data processing such as MapReduce and web search, I find that the solutions that have been developed for *physical* clusters fall short in a Xen *virtual* cluster. Second, I will provide a concrete understanding of the problem, and reveal that the situations that when the sending VM is preempted versus when the receiving VM is preempted, are different. Third, I will introduce my recent attempts on paravirtualizing TCP to overcome the negative effect caused by VM scheduling delays.Adoptive retransmission in TCP
This document summarizes different algorithms for adaptive retransmission in TCP. The original TCP specification uses an average of sample round-trip times (RTTs) to estimate the RTT and sets the timeout to twice the estimated RTT. The Karn/Partridge algorithm only measures RTT for original transmissions and uses exponential backoff for timeouts after retransmissions. The Jacobson/Karela algorithm calculates estimated RTT and deviation from it to set the timeout to the estimated RTT plus a factor times the deviation, allowing larger timeouts when variance is high.
Mobile computing-tcp data flow control
This document discusses TCP data flow control and congestion control mechanisms for mobile networks. It describes how TCP uses windows, acknowledgements, and timeouts to regulate data transmission rates. Some key challenges with directly applying TCP to mobile networks are high packet loss rates leading to frequent window resizing and reduced throughput. The document proposes methods for mobile networks like split TCP, fast retransmit/recovery, and TCP-aware link layers to address these challenges.
Leaky bucket algorithm
The document summarizes two algorithms for regulating network traffic:
1. The Leaky Bucket Algorithm models traffic as water entering a bucket with a hole, limiting output to a constant rate regardless of input rate. Packets are discarded if the bucket is full.
2. The Token Bucket Algorithm generates tokens periodically that must be removed from the bucket before packets can be transmitted, allowing bursts up to the token capacity. This is less restrictive than the Leaky Bucket Algorithm.
Tcp congestion control (1)
The document discusses TCP congestion control algorithms. It describes the Additive Increase Multiplicative Decrease (AIMD) approach where the congestion window (cwnd) is increased linearly but reduced by half when packet loss is detected. Slow start is used to quickly ramp up cwnd initially through exponential growth. Fast retransmit detects lost packets using duplicate ACKs to retransmit earlier. Fast recovery then resumes increasing cwnd after a retransmit. The document also examines algorithms for adaptive retransmission timeouts based on mean and variance of measured round-trip times.
Leaky Bucket & Tocken Bucket - Traffic shaping
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Lect9 (1)
TCP uses congestion control to prevent network congestion collapse. It uses additive increase multiplicative decrease (AIMD) where the sending rate is increased slowly but cut in half after a loss. TCP paces packets using a congestion window that limits unacknowledged data. It uses slow start to quickly reach bandwidth and congestion avoidance to increase the window by 1 packet per RTT. This models TCP behavior and shows throughput is related to window size, loss rate, and RTT.
Congestion control in TCP
TCP uses congestion control to determine how much capacity is available in the network and regulate how many packets can be in transit. It uses additive increase/multiplicative decrease (AIMD) where the congestion window is increased slowly with each ACK but halved upon timeout. Slow start is used initially and after idle periods to grow the window exponentially until congestion is detected. Fast retransmit and fast recovery help detect and recover from packet loss without requiring a timeout.
3a data link layer continued
This document discusses selective repeat automatic repeat request (ARQ) and provides examples of how it operates. Selective repeat ARQ allows frames to be received out of order, with only missing frames retransmitted. Timers are used for each sent frame, and a frame is retransmitted if its timer expires before an acknowledgment is received. The receiver waits to deliver frames until a set of consecutive frames has been received starting from the beginning of the window. Examples demonstrate frame retransmissions and acknowledgments with and without errors.
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The document proposes an enhanced distributed TCP caching (EDTC) approach to improve TCP performance over wireless sensor networks. EDTC improves upon distributed TCP caching (DTC) by detecting and handling TCP acknowledgment losses, disabling unnecessary retransmissions, and using a smoothed retransmission timeout value. Simulation results show that EDTC reduces energy consumption and transfer duration compared to DTC and TCP, especially in high packet loss networks.
Performance Evaluation of High Speed Congestion Control Protocols
This document evaluates and compares the performance of seven high-speed congestion control protocols: Bic TCP, Cubic TCP, Hamilton TCP, HighSpeed TCP, Illinois TCP, Scalable TCP and YeAH TCP. The protocols are simulated using NS-2 with multiple flows and their efficiency, fairness, and overall performance are calculated and compared for different numbers of flows. Key metrics like throughput, link utilization, and fairness index are analyzed for the protocols under varying parameters like RTT, queue size, and number of flows. Cubic TCP and Bic TCP generally showed better performance than the other protocols based on the simulations.
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Here are the key steps of reverse path broadcasting/multicasting using the example network:
1. Router S sends the multicast packet and all routers know the shortest path to S is directly through S.
2. Router directly connected to S forwards the packet to all other ports except the port it arrived on (parent port).
3. Subsequent routers forward the packet to all ports except the parent port, following the shortest path to S in reverse.
4. This process continues until all destinations are reached, with each router forwarding only once.
The end result is an efficient multicast distribution tree is built to reach all destinations.
Redesigning MPTCP in Edge clouds
The document proposes RAMPTCP, a receiver-assisted extension to MPTCP for edge clouds. RAMPTCP aims to improve MPTCP performance in edge-to-edge networks by having the receiver send network condition information to help the sender make better scheduling decisions. Preliminary ns3 simulations show RAMPTCP achieves around 19% higher throughput and 58% fewer retransmissions compared to default MPTCP in a scenario where one network path experiences packet loss. Future work includes incorporating different access technologies and developing effective RAMPTCP control actions.
chapter 3.2 TCP.pptx
TCP provides reliable data transfer through several key features:
- It numbers data bytes and uses acknowledgments to ensure all bytes are received correctly. If bytes are lost, they are retransmitted.
- Congestion control algorithms like slow start and congestion avoidance allow TCP to gradually increase data transfer rates while avoiding overwhelming the network.
- Fast retransmit detects lost packets sooner by retransmitting on three duplicate ACKs, while fast recovery resumes data transfer using ACKs still in the pipe.
Lecture 19 22. transport protocol for ad-hoc
This document discusses transport layer protocols for mobile ad hoc networks (MANETs). It begins with an introduction to MANETs and the need for new network architectures and protocols to support new types of networks. It then provides an overview of TCP/IP and how TCP works, including congestion control mechanisms. The document discusses challenges for TCP over wireless networks, where packet losses are often due to errors rather than congestion. It covers different versions of TCP and their approaches to congestion control. The goal is to design transport layer protocols that can address the unreliable links and frequent topology changes in MANETs.
TCP Theory
TCP provides reliable data transfer over unreliable packet networks by using acknowledgments, retransmissions, and adaptive congestion control. It works with IP to transfer data through routers that may drop packets. While TCP ensures reliable delivery, it must control its transmission rate to avoid overwhelming network capacity and causing congestion collapse. This is achieved through additive-increase, multiplicative-decrease of the congestion window and techniques like active queue management.
Designing TCP-Friendly Window-based Congestion Control
TFWC is a proposed window-based congestion control algorithm that is designed to be TCP-friendly for real-time multimedia applications, while addressing some issues with the standard rate-based TFRC algorithm. TFWC uses a TCP-like acknowledgment clock and window sizing equation to achieve smooth throughput similar to TFRC, but provides better fairness when competing with TCP traffic and is simpler to implement without needing to measure round-trip times. Analysis shows that TFWC provides fairness comparable to TFRC, smoothness on par with TFRC, and faster responsiveness to changes in available bandwidth.
UDT
The document summarizes the UDT protocol, which is a high performance transport protocol designed for data-intensive applications over high-speed networks. It discusses the limitations of TCP for these applications and high bandwidth-delay product networks. It then provides an overview of the design and implementation of the UDT protocol, including its congestion control algorithm, APIs, and composable framework. It evaluates UDT's performance in terms of efficiency, fairness, and stability compared to TCP. The goal of UDT is to enable efficient, fair, and friendly transport of data for distributed applications over high-speed networks.
TCP Over Wireless
This document discusses TCP over wireless networks. It explains that TCP was designed for fixed networks with low delay and errors, but wireless networks have high delay, errors and variable bandwidth. This causes TCP to perform poorly over wireless. The document outlines various techniques to improve TCP performance over wireless like Fast Retransmit and Recovery, Slow Start proposals with larger initial windows, ACK counting and ACK-every-segment. It also discusses protocols like HTTP, RLP that operate between TCP and the wireless transmission layers.
RIPE 80: Buffers and Protocols
APNIC Chief Scientist Geoff Huston presents on Buffers and Protocols at RIPE 80, held online from 12 to 14 May 2020.
Programming TCP for responsiveness
The document discusses optimizations to TCP and HTTP/2 to improve responsiveness on the web. It describes how TCP slow start works and the delays introduced in standard HTTP/2 usage from TCP/TLS handshakes. The author proposes adjusting the TCP send buffer polling threshold to allow switching between responses more quickly based on TCP congestion window state. Benchmark results show this can reduce response times by eliminating an extra round-trip delay.
TLS in manet
The document discusses challenges with using TCP in mobile ad hoc networks (MANETs) and evaluates potential solutions. Specifically, it finds that:
1) TCP performs poorly in MANETs due to high packet loss from route failures and wireless errors, which TCP misinterprets as congestion.
2) TCP variants like Westwood and Jersey that more accurately estimate bandwidth perform better but are not sufficient.
3) A new transport protocol like ATP that is rate-based rather than window-based and leverages intermediate nodes may better address MANET issues.
Tcp traffic control and red ecn
This document summarizes key aspects of TCP traffic control as covered in Chapter 12. It discusses TCP flow and congestion control, including how the transmission rate is determined by incoming ACKs. It then covers traffic control fields in the TCP header, credit allocation mechanisms, and the impact of window size on throughput. The document also summarizes TCP congestion control techniques like slow start, congestion avoidance, fast retransmit, fast recovery, and limited transmit. It notes the differentiating impact of "mice vs. elephant" flows on network congestion.
UAV Data Link Design for Dependable Real-Time Communications
Communication over the kinds of Data-Links used for unmanned vehicles presents important challenges dues to the low bandwidth, intermittent, and lower reliability of these links. Classic network protocols such as TCP do not operate well in this environment forcing application developers to implement their own reliability and session management. This presentation describes he issues and alternatives.
UDT
The document describes the design and implementation of a new high performance data transport protocol called UDT. UDT is implemented at the application layer over UDP to provide reliable, high-speed data transfer capabilities. It includes a new congestion control algorithm based on AIMD with decreasing increases that aims for efficiency, fairness and friendliness. Experimental results show UDT achieves high throughput and good fairness compared to TCP. The document also introduces a configurable framework called Composable UDT that allows new congestion control algorithms to be easily implemented and evaluated.
NE #1.pptx
1) Congestion occurs when there are too many sources sending too much data too fast for the network to handle, leading to lost packets and long delays. TCP uses congestion control to address this problem.
2) TCP uses Additive Increase Multiplicative Decrease (AIMD) congestion control, where it slowly increases the transmission rate and halves it upon detecting packet loss, exhibiting a sawtooth pattern.
3) Key TCP congestion control mechanisms include slow start for initial exponential increase, fast retransmit to quickly retransmit lost packets based on duplicate ACKs, and fast recovery to resume transmission after a fast retransmit.
Similar to DCTcp (20)
Improving Distributed TCP Caching for Wireless Sensor Networks
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Performance Evaluation of High Speed Congestion Control Protocols
Performance Evaluation of High Speed Congestion Control Protocols
Iaetsd an effective approach to eliminate tcp incast
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Designing TCP-Friendly Window-based Congestion Control
Designing TCP-Friendly Window-based Congestion Control
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UAV Data Link Design for Dependable Real-Time Communications
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LoRa is a long range wireless radio technology for low power wide area networks (LPWANs) used in IoT and M2M applications. It uses license-free sub-GHz frequency bands and spreads signals over a wide bandwidth for long-range transmissions of up to 5-15 km in rural areas and 2-5 km in urban areas using low power consumption from battery-powered devices. The LoRa Alliance oversees the LoRaWAN standard to enable interoperability.
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The document provides an overview of SDN and related technologies demonstrated in a Dell lab, including:
1. SDN allows separation of the control plane and data plane in networking devices using an abstraction layer and OpenFlow protocol for communication between controllers and switches.
2. The lab topology included VLT and MLAG for redundancy between switches, as well as a Big Monitoring Fabric using Dell switches and a controller to provide network packet brokering without dedicated devices.
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DCTcp
- 1. DCTCP Data Center TCP Oded Rotter oded1233@gmail.com Based On: Microsoft Research Stanford University http://www.stanford.edu/~alizade/Site/DCTCP.html
- 2. TCP • שכבת ה- Transportהמשמעותית ב-Data Center • פופולארי וידוע • לא מושלם ....
- 3. דרישות מ- TCPבסביבת Data Center (חשוב מאוד שיתקיימו יחד) • התמודדות עם התפרצויות רגעיות של תעבורה • שיהוי נמוך • Throughputגבוה
- 4. DCTCP is an enhancement to the TCP congestion control algorithm for data center networks. It leverages Explicit Congestion Notification (ECN), a feature which is increasingly becoming available in modern data center switches. DCTCP sources extract multi-bit feedback on congestion from the single-bit stream of ECN marks by estimating the fraction of marked packets. In doing so, DCTCP sources react to the extent of congestion, not just the presence of congestion as in TCP. This finer level of control allows DCTCP to operate with very low buffer occupancies while simultaneously achieving high throughput.
- 5. How … • Maintain small queues, without loss of throughput • Buffer sizing problem : • A single flow needs buffers for 100% Throughput. • Large # of flows: is enough.
- 6. Data Center TCP Algorithm B K Don’t Switch side: Mark Mark – Mark packets when Queue Length > K. Sender side: – Maintain running average of fraction of packets marked (α). In each RTT: Adaptive window decreases: – Note: decrease factor between 1 and 2. 19
- 7. ... סבלנות, עוד קצת גראפים Packets sent in this Window Size RTT are marked. W*+1 W* (W*+1)(1-α/2) Time 85% Less Buffer than TCP
- 8. לסיכום • DCTCPעונה על הדרישות שלנו • אין שינוי מהותי ב-TCP • המתגים מסוגלים לבצע זאת בחומרה קיימת 72