IEEE1588 - Collision avoidance for Delay_Req messages in broadcast media
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This presentation has been given during ISPCS in 2009. The full paper is available form http://eprints.adm.unipi.it/.
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![Collision avoidance for Delay_Req messages in broadcast media Augusto Ciuffoletti [email_address] Università degli Studi di Pisa Dipartimento di Informatica](https://image.slidesharecdn.com/slides-091009160509-phpapp01/85/IEEE1588-Collision-avoidance-for-Delay_Req-messages-in-broadcast-media-1-320.jpg)
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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.
go back n protocol
This document discusses the Go Back N protocol. It explains that Go Back N is used when transmission times are large or bandwidth is high. It allows the sender to transmit multiple frames before waiting for acknowledgments. This increases efficiency but requires buffering of frames at the sender. An error may require retransmission of multiple correct frames received after the erroneous one. Advantages are increased efficiency and low waiting times by varying the sender window size, but disadvantages include high buffer needs and resending correct frames after errors.
Sliding window protocol
This document describes the sliding window protocol. It discusses key concepts like both the sender and receiver maintaining buffers to hold packets, acknowledgements being sent for every received packet, and the sender being able to send a window of packets before receiving an acknowledgement. It then explains the sender side process of numbering packets and maintaining a sending window. The receiver side maintains a window size of 1 and acknowledges by sending the next expected sequence number. A one bit sliding window protocol acts like stop and wait. Merits include multiple packets being sent without waiting for acknowledgements while demerits include potential bandwidth waste in some situations.
Go back-n protocol
Go-Back-N (GBN) is an ARQ protocol that allows a sender to transmit multiple frames before receiving an acknowledgement. The sender maintains a window of size N, meaning it can transmit N frames before waiting for a response. The receiver window is always size 1, acknowledging frames individually. If a frame times out without an ACK, the sender retransmits that frame and all subsequent frames in the window. GBN improves efficiency over stop-and-wait by allowing transmission of multiple frames while reducing waiting time at the sender.
Chapter 11
The document discusses various data link layer protocols including framing, flow control, error control, Stop-and-Wait, Go-Back-N, Selective Repeat ARQ, HDLC, and PPP. It provides algorithms and examples to illustrate how each protocol handles framing, flow control, and error correction over both noiseless and noisy channels. Key aspects covered include sequence numbers, acknowledgments, timers, windows, and retransmission methods.
GO BACK N PROTOCOL
Go-Back-N and Selective Repeat are two data transmission protocols. Go-Back-N allows the sender to transmit multiple packets before receiving ACKs, but retransmits all packets after the lost packet when an error occurs. Selective Repeat retransmits only the packet with errors, avoiding unnecessary retransmissions. It uses buffers to store packets for potential retransmission, handling errors more efficiently than Go-Back-N when delays or data rates are high.
Module15: Sliding Windows Protocol and Error Control
Here are the key steps in stop-and-wait ARQ when frame 1 is lost:
1. Station A transmits frame 0 and waits for ACK
2. Station B receives frame 0 and sends ACK
3. Station A receives ACK and transmits frame 1
4. Frame 1 is lost in transmission
5. Station A's timer expires before receiving ACK for frame 1
6. Station A retransmits frame 1
The key aspects are that the sender transmits one frame at a time and waits for ACK before sending the next frame. If ACK is not received within the timeout period, the frame is retransmitted.
Importance of sliding window protocol
Abstract The data can get lost, reordered or duplicated due to the presence of routers and buffer space over the unreliable channel in the conventional networks. The data link layer deals with frame formation, flow control, error control, and addressing and link management. All such functions will be performed only by data link protocols. The sliding window protocol will detect and correct error if the received data have enough redundant bits or repeat a retransmission of data. The paper shows the working of this duplex protocol of data link network. Keywords: ACK, GOBACK, ARQ, NACK.
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3a data link layer continued
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go back n protocol
This document discusses the Go Back N protocol. It explains that Go Back N is used when transmission times are large or bandwidth is high. It allows the sender to transmit multiple frames before waiting for acknowledgments. This increases efficiency but requires buffering of frames at the sender. An error may require retransmission of multiple correct frames received after the erroneous one. Advantages are increased efficiency and low waiting times by varying the sender window size, but disadvantages include high buffer needs and resending correct frames after errors.
Sliding window protocol
This document describes the sliding window protocol. It discusses key concepts like both the sender and receiver maintaining buffers to hold packets, acknowledgements being sent for every received packet, and the sender being able to send a window of packets before receiving an acknowledgement. It then explains the sender side process of numbering packets and maintaining a sending window. The receiver side maintains a window size of 1 and acknowledges by sending the next expected sequence number. A one bit sliding window protocol acts like stop and wait. Merits include multiple packets being sent without waiting for acknowledgements while demerits include potential bandwidth waste in some situations.
Go back-n protocol
Go-Back-N (GBN) is an ARQ protocol that allows a sender to transmit multiple frames before receiving an acknowledgement. The sender maintains a window of size N, meaning it can transmit N frames before waiting for a response. The receiver window is always size 1, acknowledging frames individually. If a frame times out without an ACK, the sender retransmits that frame and all subsequent frames in the window. GBN improves efficiency over stop-and-wait by allowing transmission of multiple frames while reducing waiting time at the sender.
Chapter 11
The document discusses various data link layer protocols including framing, flow control, error control, Stop-and-Wait, Go-Back-N, Selective Repeat ARQ, HDLC, and PPP. It provides algorithms and examples to illustrate how each protocol handles framing, flow control, and error correction over both noiseless and noisy channels. Key aspects covered include sequence numbers, acknowledgments, timers, windows, and retransmission methods.
GO BACK N PROTOCOL
Go-Back-N and Selective Repeat are two data transmission protocols. Go-Back-N allows the sender to transmit multiple packets before receiving ACKs, but retransmits all packets after the lost packet when an error occurs. Selective Repeat retransmits only the packet with errors, avoiding unnecessary retransmissions. It uses buffers to store packets for potential retransmission, handling errors more efficiently than Go-Back-N when delays or data rates are high.
Module15: Sliding Windows Protocol and Error Control
Here are the key steps in stop-and-wait ARQ when frame 1 is lost:
1. Station A transmits frame 0 and waits for ACK
2. Station B receives frame 0 and sends ACK
3. Station A receives ACK and transmits frame 1
4. Frame 1 is lost in transmission
5. Station A's timer expires before receiving ACK for frame 1
6. Station A retransmits frame 1
The key aspects are that the sender transmits one frame at a time and waits for ACK before sending the next frame. If ACK is not received within the timeout period, the frame is retransmitted.
Importance of sliding window protocol
Abstract The data can get lost, reordered or duplicated due to the presence of routers and buffer space over the unreliable channel in the conventional networks. The data link layer deals with frame formation, flow control, error control, and addressing and link management. All such functions will be performed only by data link protocols. The sliding window protocol will detect and correct error if the received data have enough redundant bits or repeat a retransmission of data. The paper shows the working of this duplex protocol of data link network. Keywords: ACK, GOBACK, ARQ, NACK.
Solution8 v2
1. The document provides solutions to problems regarding database replication.
2. For a read-only replicated database, availability improves as more replicas are added. However, for an update-only replicated database, availability can decrease if the replication protocol requires updating all replicas for a transaction to commit.
3. The replication protocol described, where transactions execute on one server and propagate updates to the other server within the transaction boundary using two-phase locking and two-phase commit, does not provide one-copy serializability. A history is provided as a counterexample.
Flow & Error Control
The document discusses various topics related to flow and error control in computer networks, including stop-and-wait ARQ, sliding window protocols, and selective reject ARQ. Stop-and-wait ARQ allows transmission of one frame at a time, while sliding window protocols allow multiple outstanding frames using sequence numbers and acknowledgments. Go-back-N ARQ requires retransmission of frames from the lost frame onward, while selective reject ARQ only retransmits the lost frame to minimize retransmissions.
Flow control
Flow control refers to procedures that restrict how much data a sender can transmit before receiving an acknowledgement from the receiver. This controls congestion by ensuring the receiving device does not exceed its limited speed and capacity. TCP provides flow control through a sliding window mechanism using the receiver window, which indicates how much free buffer space is available at the receiver to store incoming data. The sender limits its transmissions based on this window to avoid overflowing the receiver's buffer.
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.
Leakybucketalgorithm
This document discusses 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 and removes a token for each packet sent. This allows bursts proportional to the number of tokens, rather than rigidly limiting output. It is implemented with a counter that is incremented with new tokens and decremented when packets are sent.
Leaky Bucket & Tocken Bucket - Traffic shaping
This presentation provides a description about the traffic shaping in computer network like leaky bucket and token bucket and their differences
Flow Control
Flow control specifies how much data a sender can transmit before receiving permission to continue. There are two main types of flow control: stop-and-wait and sliding window. Stop-and-wait allows transmission of one frame at a time, while sliding window allows transmitting multiple frames before needing acknowledgement. Sliding window flow control uses variables like window size, last ACK received, and last frame sent to determine how transmission proceeds. It provides more efficiency than stop-and-wait. Automatic repeat request (ARQ) handles retransmission of lost or damaged frames through timeouts, negative acknowledgements, or cumulative acknowledgements depending on the specific ARQ protocol used.
Importance of sliding window protocol
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
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”.
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.
Sliding window protocol(ARQ technique)
The document discusses different types of Automatic Repeat Request (ARQ) techniques used for error control in data transmission. It describes Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. Go-Back-N ARQ allows sending multiple frames before receiving acknowledgments. If a frame is lost or corrupted, the sender retransmits that frame and all subsequent frames. Selective Repeat ARQ only retransmits the damaged frame, making it more bandwidth efficient but also more complex since the receiver must buffer frames. The sizes of the sender and receiver windows are important parameters that impact the efficiency of the protocols.
Go Back N Arq1
This document discusses Go-Back-N ARQ, a method for error control in data transmission that uses pipelining and sliding windows. It introduces the concept of using sequence numbers, timers, acknowledgements, and resending frames to improve efficiency over Stop-and-Wait ARQ. Go-Back-N ARQ allows the sender to send multiple frames before receiving ACKs, but requires resending all frames after the lost one. It has higher efficiency than Stop-and-Wait but also has disadvantages related to buffering requirements and wasted bandwidth.
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.
Retransmission Tcp
TCP uses a retransmission queue and timers to reliably retransmit lost data segments. Each sent segment is placed on the queue and given a retransmission timer. If an acknowledgment is not received before the timer expires, the segment is retransmitted. There are different policies for handling retransmissions of subsequent outstanding segments. TCP also adapts retransmission timers dynamically based on measurements of the round-trip time between devices to account for varying network conditions. The window size advertised by a receiving device controls the amount of outstanding data and affects the sending rate.
Sliding window protocol
Sliding window protocols number data frames, allow lost frames to be retransmitted, and handle duplicate and out-of-order frames. The sender and receiver each maintain variables to track the oldest unacknowledged frame and next frame number. The difference between the variables is the window size. The algorithm involves transmitting frames within the window, acknowledging received frames to advance the windows, retransmitting on timeouts, and using negative acknowledgments for missing frames. Window sizes are limited by the number of sequence number bits to avoid duplicates.
TCP Westwood
¤ 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.
Chapter 12
This document discusses multiple access protocols for wireless networks. It describes random access methods like ALOHA and slotted ALOHA, controlled access methods using reservation, polling, and token passing, and channelization methods including FDMA, TDMA, and CDMA. Examples are provided to illustrate the calculation of throughput for various access loads in ALOHA and slotted ALOHA networks.
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.
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.
Stop And Wait ARQ
Stop and wait ARQ is an error-control method for reliable data transmission over unreliable services. It uses acknowledgements and timeouts to ensure reliable transmission. In stop and wait ARQ, the transmitter sends a single frame and waits for an acknowledgement before sending the next frame. Sequence numbers are needed to identify frames and acknowledgements. The sender and receiver algorithms involve waiting for events, sending/receiving frames, checking for errors, acknowledging correct frames, and resending lost frames after timeouts. While simple, it has low efficiency due to sending only one frame at a time and setting a timer for each frame.
Monitoring a virtual network infrastructure - An IaaS perspective
The document discusses the challenges of providing network resources as part of an Infrastructure as a Service (IaaS) cloud computing model. While IaaS has traditionally focused on storage and computing resources, the networking capabilities now exist to provision virtual network infrastructure as well. However, IaaS providers still typically only offer flat local area networks rather than composite network topologies that some users require. The key technology that enables virtual private networks is virtual bridging using VLAN tagging, which allows flexible virtual network configurations. For network monitoring in IaaS, a proxy that interacts with users is proposed to dynamically configure monitoring while maintaining provider control over network devices.
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1. The document provides solutions to problems regarding database replication.
2. For a read-only replicated database, availability improves as more replicas are added. However, for an update-only replicated database, availability can decrease if the replication protocol requires updating all replicas for a transaction to commit.
3. The replication protocol described, where transactions execute on one server and propagate updates to the other server within the transaction boundary using two-phase locking and two-phase commit, does not provide one-copy serializability. A history is provided as a counterexample.
Flow & Error Control
The document discusses various topics related to flow and error control in computer networks, including stop-and-wait ARQ, sliding window protocols, and selective reject ARQ. Stop-and-wait ARQ allows transmission of one frame at a time, while sliding window protocols allow multiple outstanding frames using sequence numbers and acknowledgments. Go-back-N ARQ requires retransmission of frames from the lost frame onward, while selective reject ARQ only retransmits the lost frame to minimize retransmissions.
Flow control
Flow control refers to procedures that restrict how much data a sender can transmit before receiving an acknowledgement from the receiver. This controls congestion by ensuring the receiving device does not exceed its limited speed and capacity. TCP provides flow control through a sliding window mechanism using the receiver window, which indicates how much free buffer space is available at the receiver to store incoming data. The sender limits its transmissions based on this window to avoid overflowing the receiver's buffer.
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.
Leakybucketalgorithm
This document discusses 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 and removes a token for each packet sent. This allows bursts proportional to the number of tokens, rather than rigidly limiting output. It is implemented with a counter that is incremented with new tokens and decremented when packets are sent.
Leaky Bucket & Tocken Bucket - Traffic shaping
This presentation provides a description about the traffic shaping in computer network like leaky bucket and token bucket and their differences
Flow Control
Flow control specifies how much data a sender can transmit before receiving permission to continue. There are two main types of flow control: stop-and-wait and sliding window. Stop-and-wait allows transmission of one frame at a time, while sliding window allows transmitting multiple frames before needing acknowledgement. Sliding window flow control uses variables like window size, last ACK received, and last frame sent to determine how transmission proceeds. It provides more efficiency than stop-and-wait. Automatic repeat request (ARQ) handles retransmission of lost or damaged frames through timeouts, negative acknowledgements, or cumulative acknowledgements depending on the specific ARQ protocol used.
Importance of sliding window protocol
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
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”.
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.
Sliding window protocol(ARQ technique)
The document discusses different types of Automatic Repeat Request (ARQ) techniques used for error control in data transmission. It describes Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. Go-Back-N ARQ allows sending multiple frames before receiving acknowledgments. If a frame is lost or corrupted, the sender retransmits that frame and all subsequent frames. Selective Repeat ARQ only retransmits the damaged frame, making it more bandwidth efficient but also more complex since the receiver must buffer frames. The sizes of the sender and receiver windows are important parameters that impact the efficiency of the protocols.
Go Back N Arq1
This document discusses Go-Back-N ARQ, a method for error control in data transmission that uses pipelining and sliding windows. It introduces the concept of using sequence numbers, timers, acknowledgements, and resending frames to improve efficiency over Stop-and-Wait ARQ. Go-Back-N ARQ allows the sender to send multiple frames before receiving ACKs, but requires resending all frames after the lost one. It has higher efficiency than Stop-and-Wait but also has disadvantages related to buffering requirements and wasted bandwidth.
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.
Retransmission Tcp
TCP uses a retransmission queue and timers to reliably retransmit lost data segments. Each sent segment is placed on the queue and given a retransmission timer. If an acknowledgment is not received before the timer expires, the segment is retransmitted. There are different policies for handling retransmissions of subsequent outstanding segments. TCP also adapts retransmission timers dynamically based on measurements of the round-trip time between devices to account for varying network conditions. The window size advertised by a receiving device controls the amount of outstanding data and affects the sending rate.
Sliding window protocol
Sliding window protocols number data frames, allow lost frames to be retransmitted, and handle duplicate and out-of-order frames. The sender and receiver each maintain variables to track the oldest unacknowledged frame and next frame number. The difference between the variables is the window size. The algorithm involves transmitting frames within the window, acknowledging received frames to advance the windows, retransmitting on timeouts, and using negative acknowledgments for missing frames. Window sizes are limited by the number of sequence number bits to avoid duplicates.
TCP Westwood
¤ 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.
Chapter 12
This document discusses multiple access protocols for wireless networks. It describes random access methods like ALOHA and slotted ALOHA, controlled access methods using reservation, polling, and token passing, and channelization methods including FDMA, TDMA, and CDMA. Examples are provided to illustrate the calculation of throughput for various access loads in ALOHA and slotted ALOHA networks.
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.
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.
Stop And Wait ARQ
Stop and wait ARQ is an error-control method for reliable data transmission over unreliable services. It uses acknowledgements and timeouts to ensure reliable transmission. In stop and wait ARQ, the transmitter sends a single frame and waits for an acknowledgement before sending the next frame. Sequence numbers are needed to identify frames and acknowledgements. The sender and receiver algorithms involve waiting for events, sending/receiving frames, checking for errors, acknowledging correct frames, and resending lost frames after timeouts. While simple, it has low efficiency due to sending only one frame at a time and setting a timer for each frame.
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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.
Comparative Analysis of Different TCP Variants in Mobile Ad-Hoc Network
The document analyzes the performance of different TCP variants (New Reno, Reno, Tahoe) with MANET routing protocols (AODV, DSR, TORA) through simulation. It finds that in scenarios with 3 and 5 nodes, AODV has better throughput than DSR and TORA for all TCP variants. Throughput decreases for all variants as node count increases. New Reno provides multiple packet loss recovery and is the best choice for AODV in MANETs due to its consistent performance with changes in node count. Further analysis of additional protocols and TCP variants is recommended.
Unit IV_Flow.pptx
Flow control is used to prevent a sender from overwhelming a receiver. It uses feedback from the receiver to control sending. Stop-and-wait protocols only allow one frame to be sent before waiting for acknowledgement. Go-back-n protocols allow multiple unacknowledged frames but require resending all frames if any are lost. Selective repeat protocols only resend lost frames to improve efficiency.
Lec9
This document summarizes a lecture on the transport layer and reliable data transmission. It discusses:
- The role of the transport layer in multiplexing data between applications on hosts and providing end-to-end services like reliable delivery.
- The two main transport protocols, TCP and UDP. TCP provides reliable byte-stream delivery while UDP is minimal and unreliable.
- How ports are used for demultiplexing at the transport layer, mapping sockets to processes.
- Challenges in providing reliable transport given that packets can be corrupted, lost, delayed or reordered by the network. Solutions involve sequence numbers, acknowledgments, timeouts and retransmissions.
Mobile Transpot Layer
This document discusses various transport layer protocols for mobile networks. It begins by describing TCP and its mechanisms for congestion avoidance, flow control, slow start, and retransmission. It then covers several TCP variants including Tahoe, Reno, and Vegas. It also discusses indirect TCP, Snoop TCP, and Mobile TCP which aim to optimize TCP for wireless networks by handling retransmissions locally or splitting the connection. The document provides details on the algorithms and functioning of these different protocols.
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.A Performance Comparison of TCP Protocols
The performance of wireless ad hoc networks is impacted significantly by the way TCP reacts to lost packets. TCP was designed specifically for wired, reliable networks; thus, any packet loss is attributed to congestion in the network. This assumption does not hold in wireless networks as most packet loss is due to link failure. In our research we analyzed several implementations of TCP, including TCP Vegas, TCP Feedback, and SACK TCP, by measuring throughput, retransmissions, and duplicate acknowledgements through simulation with ns-2. We discovered that TCP throughput is related to the number of hops in the path, and thus depends on the performance of the underlying routing protocol, which was DSR in our research.
Mobile transport layer
The document discusses various transport layer protocols for mobile networks, including traditional TCP, Indirect TCP, Snooping TCP, and Mobile TCP. Traditional TCP was designed for fixed networks and experiences issues in mobile networks due to factors like packet loss from handoffs. Indirect TCP splits the TCP connection at the access point to isolate the wireless link. Snooping TCP has the access point buffer packets and detect losses to enable local retransmissions. Mobile TCP uses a supervisory host to handle disconnections and restart the connection when needed. Each approach aims to improve TCP performance over mobile networks while maintaining compatibility with traditional TCP.
Connection Establishment & Flow and Congestion Control
On these slides i describe all the detail about Connection Establishment & Flow and Congestion Control. For more detail visit: https://chauhantricks.blogspot.com/
connectionestablishmentflowandcongestioncontrol-190130165746.pdf
A connection must be established before data exchange can occur using connection-oriented protocols like TCP. Connection establishment involves a three-way handshake between the two endpoints to synchronize sequence numbers and negotiate parameters. Flow control mechanisms like stop-and-wait and sliding windows are used to ensure the sender's transmission rate matches the receiver's processing capabilities. Congestion control algorithms detect and mitigate network congestion to maintain high throughput and low delay.
Data link layer (Unit 2).pdf
The document summarizes key aspects of the data link layer, including that it provides node-to-node communication, error control methods like CRC and checksum, access control methods like CSMA/CD, uses physical addresses, and sends data in frames. It then discusses flow control methods at the data link layer like stop-and-wait ARQ and sliding window protocols, providing details on how each method works, advantages, disadvantages, and examples.
High Performance Networking with Advanced TCP
High Performance Networking with TCP. TCP properties, UDP, flow control, Congestion Avoidance & Control, slow start, Congestion Control Review, TCP Tahoe & Reno
[IJET-V1I3P12] Authors :Inchara K, Shreenath K N,Dr.Srinivasa K G
[IJET-V1I3P12] Authors :Inchara K, Shreenath K N,Dr.Srinivasa K GIJET - International Journal of Engineering and Techniques
Many energy-efficient Receiver Initiated Asynchronous Duty-Cycle MAC protocol for wireless sensor
networks (WSNs) have been proposed. Most nodes suffer from significant performance Degradation for burst traffic,
due to randomly waking up to communicate with each other. The proposed protocol is new receiver initiated
asynchronous duty-cycle MAC protocol for burst traffic . By adaptively adjusting beacon time of the receiver and it
schedules the sender listening time based on scheduled period, by this high energy efficiency and low end-to-end packet
delivery latency for burst traffic is achieved. We have evaluated the performance of MAC through detailed ns- 2
simulation. The simulation results show that this protocol reduce end-to-end packet delivery latency and energy
consumption under various data rates in different topologies compared with RI-MAC.
Keywords— Wireless sensor networks, duty-cycle, receiver-initiated, low latency, energy-efficientA Survey on Cross Layer Routing Protocol with Quality of Service
Wireless is playing the wide role in today’s industrial application. Central idea of this paper is to enhance quality of service (QoS) for multimedia transmission over ad-hoc network. This paper describes the operational of different QoS routing protocols, their properties and various parameters advantages and disadvantages. Also describes the use of QoS in Cross layer routing protocol. Finally, it concludes by study of all these cross layer QoS routing protocols.
G028033037
1. The document analyzes TCP Vegas congestion control in Linux 2.6.1. TCP Vegas monitors the difference between expected sending rate and actual sending rate to estimate network congestion and adjust the congestion window size accordingly.
2. The key aspects of TCP Vegas analyzed are delay, fairness, and loss properties. TCP Vegas aims to keep a small, stable number of packets buffered to minimize delay while achieving weighted proportional fairness between connections. It avoids packet loss by carefully extracting congestion information from round-trip times.
3. Analysis shows that in Linux implementation, TCP Vegas increases and decreases the congestion window cautiously in response to traffic, avoiding sharp increases in window size that could lead to congestion like in TCP
NetWork Design Question2.) How does TCP prevent Congestion Dicuss.pdf
NetWork Design Question
2.) How does TCP prevent Congestion? Dicuss the information identifying congestion in the
network as well as the mechanism for reducing congestion?
Solution
Congestion is a problem that occurs on shared networks when multiple users contend for access
to the same resources (bandwidth, buffers, and queues).
Transmission Control Protocol (TCP) uses a network congestion-avoidance algorithm that
includes various aspects of an additive increase/multiplicative decrease (AIMD) scheme, with
other schemes such as slow-start to achieve congestion avoidance.
The TCP congestion-avoidance algorithm is the primary basis for congestion control in the
Internet.
Congestion typically occurs where multiple links feed into a single link, such as where internal
LANs are connected to WAN links. Congestion also occurs at routers in core networks where
nodes are subjected to more traffic than they are designed to handle.
TCP/IP networks such as the Internet are especially susceptible to congestion because of their
basic connection- less nature. There are no virtual circuits with guaranteed bandwidth. Packets
are injected by any host at any time, and those packets are variable in size, which make
predicting traffic patterns and providing guaranteed service impossible. While connectionless
networks have advantages, quality of service is not one of them.
Shared LANs such as Ethernet have their own congestion control mechanisms in the form of
access controls that prevent multiple nodes from transmitting at the same time.
Identifying:
Congestion is primarily reflected by a conventional user feeling-- slowness. This statement
reflects the change in the network effective flow, that is the time required to transmit an entire
data from one point to another. The effective flow doenot exist as such, it consists in reality of
three seperate indicators:
*Latency:the effective flow is inversely proportional to the latency.
*Jitter:it is latency variation over time, impacts by influencing the flow latency
*Loss Rate:the theoritical bandwidth is inversely proportional to the square root of the loss rate
These Congestion symtoms allow us to rely on objective indicators to characterize it.
Mechanism to reduce congestion:
The standard fare in TCP implementations today has four standard congestion control algorithms
that are now in common use. Their usefulness has passed the test of time.
The four algorithms, Slow Start, Congestion Avoidance, Fast Retransmit and Fast Recovery are
described below. (a) Slow Start
Slow Start, a requirement for TCP software implementations is a mechanism used by the sender
to control the transmission rate, otherwise known as sender-based flow control. This is
accomplished through the return rate of acknowledgements from the receiver. In other words, the
rate of acknowledgements returned by the receiver determine the rate at which the sender can
transmit data. When a TCP connection first begins, the Slow Start algorithm initializes a
.
Mcseminar
This document discusses various transport layer protocols for mobile networks. It begins with an overview of TCP and UDP, and then describes several strategies for improving TCP performance over mobile networks, including indirect TCP (I-TCP), snooping TCP, and Mobile TCP. It also discusses congestion control strategies like slow start and fast retransmit. Overall, the document analyzes how TCP can be optimized through techniques like connection splitting, buffering, and selective retransmission to better accommodate the characteristics of wireless networks.
Ba25315321
This document summarizes a survey and analysis of various host-to-host congestion control proposals for TCP data transmission. It discusses the basic principles that underlie current host-to-host algorithms, including probing available network resources, estimating congestion through packet loss or delay, and quickly detecting packet losses. The document then analyzes specific algorithms like slow start, congestion avoidance, and fast recovery. It also examines calculating retransmission timeout and round-trip time, congestion avoidance and packet recovery techniques, and data transmission in TCP. The overall goal of these proposals is to control congestion in a distributed manner without relying on explicit network notifications.
Transport protocols
This document provides an introduction to transport layer protocols for TCP/IP networks. It discusses key elements of transport protocols including addressing, connection establishment using handshaking, connection release using timers, flow control using sliding windows, multiplexing for optimization, and crash recovery which must be handled at the application layer. The document also covers transport layer functions like data transport and providing quality of service to hide network imperfections, as well as common transport programming APIs.
Similar to IEEE1588 - Collision avoidance for Delay_Req messages in broadcast media (20)
Comparative Analysis of Different TCP Variants in Mobile Ad-Hoc Network
Comparative Analysis of Different TCP Variants in Mobile Ad-Hoc Network
XPDS13: On Paravirualizing TCP - Congestion Control on Xen VMs - Luwei Cheng,...
XPDS13: On Paravirualizing TCP - Congestion Control on Xen VMs - Luwei Cheng,...
Connection Establishment & Flow and Congestion Control
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connectionestablishmentflowandcongestioncontrol-190130165746.pdf
connectionestablishmentflowandcongestioncontrol-190130165746.pdf
[IJET-V1I3P12] Authors :Inchara K, Shreenath K N,Dr.Srinivasa K G
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A Survey on Cross Layer Routing Protocol with Quality of Service
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NetWork Design Question2.) How does TCP prevent Congestion Dicuss.pdf
NetWork Design Question2.) How does TCP prevent Congestion Dicuss.pdf
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Slides for the presentation given at the Webist 2021 conference
Abstract:
A research team that wants to validate a new IoT solution has to implement a testbed. It is a complex step
since it must provide a realistic environment, and this may require skills that are not present in the team. This
paper explores the requirements of an IoT testbed and proposes an open-source solution based on low-cost
and widely available components and technologies. The testbed implements an architecture consisting of a
collector managing several edge devices. Security levels and duty-cycle are tunable depending on the specific
application. After analyzing the testbed requirements, the paper illustrates a template that uses WiFi for the
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Lezione tenuta nel corso di Mobile and Cyber Physical Systems della Laurea Magistrale di Informatica a Pisa.
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- Le App per l'innesco di azioni: TimeControl, TweetControl e React
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Thingspeak: fondamenti
Lezione tenuta nel corso di Mobile and Cyber Physical Systems della Laurea Magistrale di Informatica a Pisa.
- Introduzione a ThingSpeak
- Pubblicazione e recupero di dati
- Pubblicazione e recupero di comandi CallBack
- Esercizi pratici in Python
Design and implementation of a low-cost modular sensor
Slides of the presentation at IEEE WiMob/SEUNet 2017, in Rome.
We exploit an overlooked feature of the ESP8266 WiFi chip, i.e. the AT commands interpreter, to implement a sensor/actuator that meets the above specifications. To test our design, we implement a library that provides a transparent wrapper for AT commands. Hardware and software are available on bitbucket.
ZHAW 2016 - OCCI for monitoring
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A demo explains how the infrastructure is generated starting from the OCCI specification.
The source of the demo (in Java) is available in the repository of the OCCI working group.
2013 03 occi-monitoring
The document discusses extending the OCCI API with monitoring capabilities. It proposes adding two new types: Collector and Sensor. The Collector would be a link that extracts operational parameters from a source resource and delivers them to a target resource. The Sensor would be a resource that processes or aggregates output from one or more Collectors, such as by filtering, interpolating, or combining monitoring data. Plugins would provide different options for parameters, transport methods, and ways to aggregate and process data.
Collision avoidance using a wandering token in the PTP protocol
Slides presented during the 2010 WIGOWIN Workshop at the Department of Computer Science in Pisa - May 26.
Full paper available at http://eprints.adm.unipi.it
Design of a secure "Token Passing" protocol
Algorithms based on the circulation of a unique token are often indicated in the coordination of distributed systems. We introduce the design of the token passing operation at application level, that exhibits the requirements of security, since the token is a sensitive resource, and scalability, since the token passing protocol must not implement security at expense of scalability. These
characteristics make our solution suitable for large scale distributed infrastructures.
The wandering token
1) The document describes a "wandering token" approach for coordinating access to shared resources among thousands of agents in a scalable way.
2) A simulation of the approach for a video on demand application showed that it protected the resource from overload while still granting regular access.
3) The wandering token circulates randomly among members, with a randomized timer governing when new tokens are generated to replace lost tokens. This provides a robust, distributed solution to coordinating access.
Network Monitoring in the age of the Cloud
The paper explores network virtualization issues related with the Cloud Computing paradigm (mainly intended as IaaS). Finally, we consider this framework from a network monitoring perspective.
The paper is an outcome of the CoreGRID working group at ERCIM.
Grid Infrastructure Architecture A Modular Approach from CoreGRID
The document discusses a modular approach to grid infrastructure architecture proposed by CoreGRID. It identifies five key functional components of a grid middleware: 1) a workflow analyzer for user interfaces and task monitoring, 2) a checkpoint manager for fault tolerance, 3) a user/account manager for authentication and accounting, 4) a resource monitor for observing resource performance, and 5) a grid information service as the backbone. These components interact through exchanging data structures published via the grid information service while addressing issues like scalability, fault tolerance and security.
Scalable concurrency control in a dynamic membership
The document summarizes research on scalable concurrency control in dynamic distributed systems using a multi-token approach. The approach proposes using a mesh overlay topology and random routing of tokens to control access to a shared resource among a large number of dynamic nodes. Experimental results showed the process converges quickly but with more tokens and worse performance than expected, requiring further tuning of the control loop dynamics.
Prototype Implementation of a Demand Driven Network Monitoring Architecture
The document summarizes a prototype implementation of an on-demand network monitoring architecture. The architecture features clients that submit monitoring requests, sensors that perform the monitoring, and agents that route requests and streams. The prototype implements the key components in Java and uses SOAP, UDP, and LDAP. It was developed over three months as a proof of concept for an on-demand approach to network monitoring at Internet scale.
Network Monitoring in the age of the Cloud
An update about the "Network Monitoring" topic for the meeting of the CoreGRID working group at EuroPar 2009.
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- 1. Collision avoidance for Delay_Req messages in broadcast media Augusto Ciuffoletti [email_address] Università degli Studi di Pisa Dipartimento di Informatica
- 5. Validation by analytical model and simulation 10/09/09
- 7. There is one master clock in charge of maintaining clock synchronized
- 8. Network is a broadcast medium with unique collision domain
- 9. Slaves require to be adjusted with Delay_Req/Delay_Resp with bounded periodicity Idea: Exploit broadcast to avoid collision 10/09/09
- 11. The (broadcast) network transports them in different times
- 12. They are serviced with some delay
- 13. Asymmetry and jitter are introduced Master Slaves Jitter Delay_Req collision 10/09/09
- 15. We assume that all slaves want to refresh their clock with the same frequency.
- 16. IEEE1588 avoids clustering of Delay_Req messages using random delays (clause 9.5.11.2)
- 17. This has the effect of keeping the density of Delay_Req events constant in time 10/09/09
- 19. n : the number of slaves
- 20. δ : the period between successive Delay_Req on one slave
- 21. Expected number of Delay_Req per time unit
- 22. λ=n/δ
- 23. To evaluate the probability of collision, we need to introduce the duration of the event τ 1-(1+r)e -r with r=λτ 10/09/09
- 24. Probability of collision τ =10 μsec N=1000 δ =1 sec p=5 10 -5 1 collision every 2000 secs 10/09/09
- 26. Lower probability of collision events with respect to random scheduling
- 28. Embedded into existing protocol 10/09/09
- 30. however
- 31. Additional control to implement the overlay ring
- 32. Additional bandwidth to implement token exchange
- 34. Compensated by (apparent) deterministic collision avoidance 10/09/09
- 36. Token carried by the same Delay_Req/Delay_Resp pair
- 37. Global view to enforce bounded return time 10/09/09
- 39. Wait to receive a token
- 40. Send the Delay_Req upon receiving a token
- 41. Deliver the token to a neighbor at random OK, but what about bounded return time? 10/09/09
- 45. “ Holding the token” is a flag in the state of the slave
- 46. The slave “holding the token” indicates, in the Delay_Req packet, the MAC of the next holder
- 47. The master may reroute the token by indicating a different token holder
- 48. Remember that we are in a broadcast network: everybody sees every packet 10/09/09
- 50. Unless MAC are locally administered
- 52. In case of ambiguity, the master disambiguates completing the MAC
- 53. In case of rerouting and ambiguity, two “Delay_Resp” are required (extra network load) 10/09/09
- 56. The figure compares native random scheduling with token scheduling
- 57. The model considers a full mesh overlay
- 58. Colliding events are discarded 10/09/09
- 60. The deviation is due to bounded degree approximation of the network 10/09/09
- 62. We use the power of broadcast (the reason of the problem) to reduce the risk of collision
- 63. Timing of Delay_Req is bounded (as required)
- 64. No network overhead (as required)
- 65. No change in message format (as required) 10/09/09