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.
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.
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.
Connection Establishment & Flow and Congestion ControlAdeel Rasheed
On these slides i describe all the detail about Connection Establishment & Flow and Congestion Control. For more detail visit: https://chauhantricks.blogspot.com/
Analytical Research of TCP Variants in Terms of Maximum ThroughputIJLT EMAS
This paper is comparative, throughput analysis, for
the TCP variants as for New Reno, Westwood & High Speed,
and it analyzes the outcomes in simulated environment for NS -3
(version 3.25) simulator with reference to multiple varying
network parameters that includes network simulation time,
router bandwidth, varying traffic source counts to observe which
is one of the best TCP variant in different scenarios. Analysis
was done using dumbbell topology to figure out the comparative
maximum throughput of TCP variants. The analysis gives result
as TCP Variant “NewReno” is good when low bandwidth is used,
while TCP Variant “HighS peed” is good in terms of using large
bandwidths in comparison to Westwood. Network traffic flow
was observed in NetAnim tool.
UNIT IV TRANSPORT LAYER 9
Introduction – Transport Layer Protocols – Services – Port Numbers – User Datagram Protocol – Transmission Control Protocol – SCTP.
WIRELESS NETWORKS _ BABU M_ unit 3 ,4 & 5 PPT
EC 6802 WIRELESS NETWORKS PPT
POWER POINT PRESENTAION ON WIRELESS NETWORKS
BABU M
ASST PROFESSOR/ ELECTRONICS AND COMMUNICATION ENGINEERING,
RMK COLLEGE OF ENGINEERING AND TECHNOLOGY
CHENNAI, THIRUVALLUR DISTRICT
Connection Establishment & Flow and Congestion ControlAdeel Rasheed
On these slides i describe all the detail about Connection Establishment & Flow and Congestion Control. For more detail visit: https://chauhantricks.blogspot.com/
Analytical Research of TCP Variants in Terms of Maximum ThroughputIJLT EMAS
This paper is comparative, throughput analysis, for
the TCP variants as for New Reno, Westwood & High Speed,
and it analyzes the outcomes in simulated environment for NS -3
(version 3.25) simulator with reference to multiple varying
network parameters that includes network simulation time,
router bandwidth, varying traffic source counts to observe which
is one of the best TCP variant in different scenarios. Analysis
was done using dumbbell topology to figure out the comparative
maximum throughput of TCP variants. The analysis gives result
as TCP Variant “NewReno” is good when low bandwidth is used,
while TCP Variant “HighS peed” is good in terms of using large
bandwidths in comparison to Westwood. Network traffic flow
was observed in NetAnim tool.
UNIT IV TRANSPORT LAYER 9
Introduction – Transport Layer Protocols – Services – Port Numbers – User Datagram Protocol – Transmission Control Protocol – SCTP.
WIRELESS NETWORKS _ BABU M_ unit 3 ,4 & 5 PPT
EC 6802 WIRELESS NETWORKS PPT
POWER POINT PRESENTAION ON WIRELESS NETWORKS
BABU M
ASST PROFESSOR/ ELECTRONICS AND COMMUNICATION ENGINEERING,
RMK COLLEGE OF ENGINEERING AND TECHNOLOGY
CHENNAI, THIRUVALLUR DISTRICT
A throughput analysis of tcp in adhoc networkscsandit
Transmission Control Protocol (TCP) is a connection oriented end-end reliable byte stream
transport layer protocol. It is widely used in the Internet.TCP is fine tuned to perform well in
wired networks. However the performance degrades in mobile ad hoc networks. This is due to
the characteristics specific to wireless networks, such as signal fading, mobility, unavailability
of routes. This leads to loss of packets which may arise either from congestion or due to other
non-congestion events. However TCP assumes every loss as loss due to congestion and invokes
the congestion control procedures. TCP reduces congestion window in response, causing unnecessary
degradation in throughput. In mobile ad hoc networks multi-hop path forwarding further
worsens the packet loss and throughput. To understand the TCP behavior and improve the
TCP performance over mobile ad hoc networks considerable research has been carried out. As
the research is still active in this area a comprehensive and in-depth study on the TCP throughput
and the various parameters that degrade the performance of TCP have been analyzed. The
analysis is done using simulations in Qualnet 5.0
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NetWork Design Question2.) How does TCP prevent Congestion Dicuss.pdfoptokunal1
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
.
IMPACT OF CONTENTION WINDOW ON CONGESTION CONTROL ALGORITHMS FOR WIRELESS ADH...cscpconf
TCP congestion control mechanism is highly dependent on MAC layer Backoff algorithms that
predict the optimal Contention Window size to increase the TCP performance in wireless adhoc
network. This paper critically examines the impact of Contention Window in TCP congestion
control approaches. The modified TCP congestion control method gives the stability of
congestion window which provides higher throughput and shorter delay than the traditional TCP. Various Backoff algorithms that are used to adjust Contention Window are simulatedusing NS2 along with modified TCP and their performance are analyzed to depict the influence of Contention Window in TCP performance considering the metrics such as throughput, delay, packet loss and end-to-end delay
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.
Abstract - The Transmission Control Protocol (TCP) is
connection oriented, reliable and end-to-end protocol that support
flow and congestion control, with the evolution and rapid growth
of the internet and emergence of internet of things IoT, flow and
congestion have clear impact in the network performance. In this
paper we study congestion control mechanisms Tahoe, Reno,
Newreno, SACK and Vegas, which are introduced to control
network utilization and increase throughput, in the performance
evaluation we evaluate the performance metrics such as
throughput, packets loss, delivery and reveals impact of the cwnd.
Showing that SACK had done better performance in terms of
numbers of packets sent, throughput and delivery ratio than
Newreno, Vegas shows the best performance of all of them.
Improving Performance of TCP in Wireless Environment using TCP-PIDES Editor
Improving the performance of the transmission
control protocol (TCP) in wireless environment has been an
active research area. Main reason behind performance
degradation of TCP is not having ability to detect actual reason
of packet losses in wireless environment. In this paper, we are
providing a simulation results for TCP-P (TCP-Performance).
TCP-P is intelligent protocol in wireless environment which
is able to distinguish actual reasons for packet losses and
applies an appropriate solution to packet loss.
TCP-P deals with main three issues, Congestion in
network, Disconnection in network and random packet losses.
TCP-P consists of Congestion avoidance algorithm and
Disconnection detection algorithm with some changes in TCP
header part. If congestion is occurring in network then
congestion avoidance algorithm is applied. In congestion
avoidance algorithm, TCP-P calculates number of sending
packets and receiving acknowledgements and accordingly set
a sending buffer value, so that it can prevent system from
happening congestion. In disconnection detection algorithm,
TCP-P senses medium continuously to detect a happening
disconnection in network. TCP-P modifies header of TCP
packet so that loss packet can itself notify sender that it is
lost.This paper describes the design of TCP-P, and presents
results from experiments using the NS-2 network simulator.
Results from simulations show that TCP-P is 4% more
efficient than TCP-Tahoe, 5% more efficient than TCP-Vegas,
7% more efficient than TCP-Sack and equally efficient in
performance as of TCP-Reno and TCP-New Reno. But we can
say TCP-P is more efficient than TCP-Reno and TCP-New
Reno since it is able to solve more issues of TCP in wireless
environment.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
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This will be used as part of your Personal Professional Portfolio once graded.
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Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
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The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
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2. Contents
Introduction
comparison between tcp and udp
Conjestion strategies
I –TCP
Snooping
Mobile tcp
2.5/3g ether networks
Points from journals
Conclusion
2
3. WHAT IS A TRANSPORT LAYER
• In computer networking, the transport layer is a conceptual
division of methods in the layered architecture of protocols in
the network stack in the Internet Protocol Suite and the Open
Systems Interconnection (OSI). The protocols of the layer
provides host-to-host communication services for
applications.[1] It provides services such as connection-
oriented data stream support, reliability, flow control,
and multiplexing.
(source wikipedia)
3
(
4. TCP UDP
It is a connection oriented
protocol
TCP is used in case of
applications in which fast
transmission of data is not
required
HTTP, FTP, SMTP Telnet etc
It rearranges data packets in the
order specified
Comparatively slow
Reliable (defines that data will
be definitely sent across)
It is a connection less protocol
It is preferred in case of the
applications which have the
priority of sending the data on
time and on faster rates
DHCP, TFTP, SNMP, RIP, VOIP
etc
No inherent ordering, the data
packets of same message may be
ordered differently
Comparatively faster
Unreliable 4
6. Con..
Data is read as a byte stream,
thus no distinguishing
indications are transmitted to
the signal message
It is heavier as it requires
three packets to set up a
socket connection, before any
user data can be sent. TCP
handles reliability and
congestion control.
TCP controls the flow of data
Packets are sent individually
and after the arrival the
packets are rearranged
UDP is lightweight due to no
ordering of messages,
no tracking connections, etc.
UDP does not have an option
for flow control
6
7. Sliding window method
This window covers unacknowledged data and the data it
can send keeping in mind the window size advertised by
the receiver.
Following figure should give you an idea about how a
sliding window looks like :
7
8. Con..
The receiver can send acknowledgement even before its
window fills up completely.
The left edge of the window can move towards right.
Neither left edge should move towards left nor right edge
should move towards left.
8
9. CONJESTION STRATEGY
Slow-start is part of the congestion control strategy used by
TCP, the data transmission protocol used by
many Internet applications. Slow-start is used in conjunction
with other algorithms to avoid sending more data than the
network is capable of transmitting, that is, to avoid
causing network congestion. Slow-start begins initially with
a congestion window size (cwnd) of 1, 2 or 10. The value of the
Congestion Window will be increased by one with,
9
10. Con..
each acknowledgement (ACK) received effectively
doubling the window size each round-trip time . The
transmission rate will be increased with slow-start
algorithm until either a loss is detected, or the receiver's
advertised window (rwnd) is the limiting factor, or the slow
start threshold (ssthresh) is reached. If a loss event occurs,
TCP assumes that it is due to network congestion and takes
steps to reduce the offered load on the network. These
measurements depend on the used TCP congestion
avoidance algorithm.
10
11. Con..
Once ss thresh is reached, TCP changes from slow-start
algorithm to the linear growth (congestion avoidance)
algorithm. At this point, the window is increased by 1
segment for each RTT.
Although the strategy is referred to as "Slow-Start", its
congestion window growth is quite aggressive, more
aggressive than the congestion avoidance phase.[9] Before
slow-start was introduced in TCP, the initial pre-congestion
avoidance phase was even faster.
The behavior upon packet loss depends on the TCP
congestion avoidance algorithm that is used.
11
12. Fast retransmit
Fast Retransmit is an enhancement to TCP that reduces
the time a sender waits before retransmitting a
lost segment.
A TCP sender uses a timer to recognize lost segments. If an
acknowledgement is not received for a particular segment
within a specified time (a function of the estimated round-
trip delay time), the sender will assume the segment was
lost in the network, and will retransmit the segment.
Duplicate acknowledgement is the basis for the fast
retransmit mechanism which works as follows: after
receiving a packet (e.g. with sequence number 1), the
receiver sends an acknowledgement by adding 1 to the
sequence number (i.e., acknowledgement number 2) which
means that the receiver received the packet number 1 and it
expects packet number 2 from the sender 12
13. CON…
Let's assume that three subsequent packets have been lost. In
the meantime the receiver receives packet numbers 5 and
6. After receiving packet number 5, the receiver sends an
acknowledgement, but still only for sequence number 2.
When the receiver receives packet number 6, it sends yet
another acknowledgement value of 2. Because the sender
receives more than one acknowledgement with the same
sequence number (2 in this example) this is
called duplicate acknowledgement.
13
14. 14
The fast retransmit enhancement works as follows: if a
TCP sender receives a specified number of
acknowledgements which is usually set to three duplicate
acknowledgements with the same acknowledge number
(that is, a total of four acknowledgements with the same
acknowledgement number), the sender can be reasonably
confident that the segment with the next higher sequence
number was dropped, and will not arrive out of order. The
sender will then retransmit the packet that was presumed
dropped before waiting for its timeout.
15. I -TCP
Indirect TCP or I-TCP segments the connection (figure
1)
no changes to the TCP protocol for hosts connected to
the wired Internet, millions of computers use (variants
of) this protocol
optimized TCP protocol for mobile hosts
splitting of the TCP connection at, e.g., the foreign
agent into 2 TCP connections, no real end-to-end
connection any longer
hosts in the fixed part of the net do not notice the
characteristics of the wireless part
15
17. 17
If CN sends packet, FA acknowledges packet and forwards
packet to MN
If MN receives packet,it acknowledges
This acknowledgement only used by CN
Similarly if MN sends packet, FA acknowledges packet and
forwards it to CN
I-TCP requires several actions as soon a handover
takes place:
The packets have to be redirected using mobile IP
The access point acts as a proxy bufferring packets for
retransmission
After handover, the old proxy forwards data to new proxy
The sockets(current state of TCP) of old proxy also migrate
to new foreign agent
20. Snooping TCP
“Transparent” extension of TCP within the foreign agent
• buffering of packets sent to the mobile host
• lost packets on the wireless link (both directions!) will
be retransmitted immediately by the mobile host or
foreign agent, respectively (so called “local”
retransmission)
• the foreign agent therefore “snoops” the packet flow
and recognizes acknowledgements in both directions,
it also filters ACKs
• changes of TCP only within the foreign agent
20
21. Snooping TCP
Data transfer from the mobile host
FA detects packet loss on the wireless link via sequence
numbers, FA answers directly with a NACK to the MH
MH can now retransmit data with only a very short delay
Integration with MAC layer
MAC layer often has similar mechanisms to those of TCP
thus, the MAC layer can already detect duplicated packets
due to retransmissions and discard them
Problems
snooping TCP does not isolate the wireless link as good as
I-TCP
snooping might be tough if packets are encrypted
21
23. Mobile TCP
Mobile TCP:
The M-TCP splits up the connection into two parts:
An unmodified TCP is used on the Standard host-
Supervisory Host section
An optimised TCP is used on the Supervisory Host-
Mobile Host section.
The Supervisory Host (SH) adorns the same role as the
proxy (Foreign Agent) in I-TCP.
The SH is responsible for exchanging data to both the
Standard host and the Mobile host.
.
23
24. Con..
Here in this approach, we assume that the error bit rate is less as
compared to other wireless links.
So if any packet is lost, the retransmission has to occur from the
original sender and not by the SH. (This also maintains the end-
to-end TCP semantic)
The SH monitors the ACKs (ACK means acknowledgement)
being sent by the MH. If for a long period ACKs have not been
received, then the SH assumes that the MH has been
disconnected (maybe due to failure or moved out of range, etc...).
If so the SH chokes the sender by setting its window size to 0.
Because of this the sender goes into persistent mode i.e. the
sender’s state will not change no matter how long the receiver is
disconnected.
This means that the sender will not try to retransmit the data
24
25. Con..
Now when the SH detects a connectivity established again
with the MH (the old SH or new SH if handover), the
window of the sender is restored to original value.
25
26. 2.5/3g ethernetworks
Tcp over 2.5g/3g ethernetworks
Learn to live with:
• Data rates: 64 kbit/s up, 115-384 kbit/s down
asymmetry: 3-6, but also up to 1000 (broadcast
systems), periodic allocation/release of channels
• High latency, high jitter, packet loss
– Suggestions:
• Large (initial) sending windows, large maximum transfer unit, selective
acknowledgement, explicit congestion notification (ECN), time stamp, no
header compression
– Already in use:
• i-mode running over FOMA
• WAP 2.0 (“TCP with wireless profile)
26
27. Points from journals
[1]The mobile TCP will dramatically improve the
throughput performance under error condition due to
wireless transmission. The mobile TCP solution introduces
a three key technologies, these are, header
conversion,selective retransmission and no slow start
mechanism, while keeping a compatibility against user
interface and inside of the Internet.Thus these network
and transport layers solution in this paper will provide a
chance to create a new type ofcommunication life based on
mobile computing.
27
28. Con..
[2] TIAP for achieving interoperability between TCP and
ATP. TAIP can be implemented as a thin layer between the
network layer and transport layer in the TCP/IP stack and
it is transparen
[3] The employment of DTLS to secure CoAP
communications raises various issues, as addressed
throughout the article, that are also recognized and the
focus of research to both the sender and the receiver
28
29. Con..
[4]
29
LS-SCTP includes path monitoring and
packet assignment mechanisms. These mechanisms monitor
the paths and stripe the packets according to their condition.
Simulation results demonstrated the effectiveness of our
proposed mechanism in providing throughput and
reliability
to mobile applications.
30. Con..
[5] A special code class, which is used for erasure decoding,
are LDPC codes, which can be described via its sparse parity
check matrix H.
30
31. REFERENCES
[1] A NETWORK AND TRANSPORT LAYERS FOR MOBILE
COMPUTING OVER INTERNET byT. OHSAWA*, K OKANOUE and
K.TAKEDA
[2] A Transport Layer Interoperability Model For Mobile
Ad-hoc Environment by Haidar Safa, Marcel Karam, Rawad
Abou
[3] End-to-end transparent transport-layer security for
Internet integrated mobile sensing devices by Jorge Granjal
and Edmundo Monteiro
[4] A Transport Layer Load Sharing Mechanism for Mobile
Wireless Hosts by Ahmed Abd El Al, Tarek Saadawi,
Myung Lee
31
32. Con…
[5] Transport Layer Coding for the Land Mobile Satellite
Channel by Harald Emst, Luca Sartorello and Sandro
Scalise
[6]wikipedia
[7] Raj Kamal, Mobile Computing, Oxford University Press,
2007
32