Spelling suggestions: "subject:"antransmission eontrol aprotocol"" "subject:"antransmission eontrol 2protocol""
1 |
TCP/IP and ATM over LEO satellite networksChotikapong, Yotsapak January 2000 (has links)
No description available.
|
2 |
Improving TCP performance over heterogeneous networks : the investigation and design of End to End techniques for improving TCP performance for transmission errors over heterogeneous data networksAlnuem, M. A. January 2009 (has links)
Transmission Control Protocol (TCP) is considered one of the most important protocols in the Internet. An important mechanism in TCP is the congestion control mechanism which controls TCP sending rate and makes TCP react to congestion signals. Nowadays in heterogeneous networks, TCP may work in networks with some links that have lossy nature (wireless networks for example). TCP treats all packet loss as if they were due to congestion. Consequently, when used in networks that have lossy links, TCP reduces sending rate aggressively when there are transmission (non-congestion) errors in an uncongested network. One solution to the problem is to discriminate between errors; to deal with congestion errors by reducing TCP sending rate and use other actions for transmission errors. In this work we investigate the problem and propose a solution using an end-to-end error discriminator. The error discriminator will improve the current congestion window mechanism in TCP and decide when to cut and how much to cut the congestion window. We have identified three areas where TCP interacts with drops: congestion window update mechanism, retransmission mechanism and timeout mechanism. All of these mechanisms are part of the TCP congestion control mechanism. We propose changes to each of these mechanisms in order to allow TCP to cope with transmission errors. We propose a new TCP congestion window action (CWA) for transmission errors by delaying the window cut decision until TCP receives all duplicate acknowledgments for a given window of data (packets in flight). This will give TCP a clear image about the number of drops from this window. The congestion window size is then reduced only by number of dropped packets. Also, we propose a safety mechanism to prevent this algorithm from causing congestion to the network by using an extra congestion window threshold (tthresh) in order to save the safe area where there are no drops of any kind. The second algorithm is a new retransmission action to deal with multiple drops from the same window. This multiple drops action (MDA) will prevent TCP from falling into consecutive timeout events by resending all dropped packets from the same window. A third algorithm is used to calculate a new back-off policy for TCP retransmission timeout based on the network's available bandwidth. This new retransmission timeout action (RTA) helps relating the length of the timeout event with current network conditions, especially with heavy transmission error rates. The three algorithms have been combined and incorporated into a delay based error discriminator. The improvement of the new algorithm is measured along with the impact on the network in terms of congestion drop rate, end-to-end delay, average queue size and fairness of sharing the bottleneck bandwidth. The results show that the proposed error discriminator along with the new actions toward transmission errors has increased the performance of TCP. At the same time it has reduced the load on the network compared to existing error discriminators. Also, the proposed error discriminator has managed to deliver excellent fairness values for sharing the bottleneck bandwidth. Finally improvements to the basic error discriminator have been proposed by using the multiple drops action (MDA) for both transmission and congestion errors. The results showed improvements in the performance as well as decreases in the congestion loss rates when compared to a similar error discriminator.
|
3 |
Improving the performance of wireless networks using frame aggregation and rate adaptationKim, Won Soo, 1975- 09 February 2011 (has links)
As the data rates supported by the physical layer increase, overheads increasingly dominate the throughput of wireless networks. A promising approach for reducing overheads is to group a number of frames together into one transmission. This can reduce the
impact of overheads by sharing headers and the time spent waiting to gain access to the transmission floor. Traditional aggregation schemes require that frames that are aggregated all be destined to
the same receiver. These approaches neglect the fact that
transmissions are broadcast and a single transmission will potentially be received by many receivers. Thus, by taking advantage of the broadcast nature of wireless transmissions, overheads can be amortized over more data and achieve more performance gain.
To show this, we design a series of MAC-based aggregation protocols
that take advantage of rate adaptation and the broadcast nature of wireless transmissions. We first show the design of a system that can aggregate both unicast and broadcast frames. Further, the system can classify TCP ACK segments so that they can be aggregated with TCP data flowing in the opposite direction. Second, we develop a rate-adaptive frame aggregation scheme that allows us to find the best aggregation size by tracking the size based on received data frames and the data rate chosen by rate adaptation. Third, we develop a multi-destination frame aggregation scheme to aggregate
broadcast frames and unicast frames that are destined for different receivers using delayed ACKs. Using a delayed ACK scheme allows multiple receivers to control transmission time of the ACKs. Finally, we extend multi-destination rate-adaptive frame aggregation to allow piggybacking of various types of metadata with user packets. This promises to lower the impact of metadata-based control protocols on data transport.
A novel aspect of our work is that we implement and validate the designs not through simulation, but rather using our wireless node
prototype, Hydra, which supports a high performance PHY based on
802.11n. To validate our designs, we conduct extensive experiments
both on real and emulator-based channels and measure system
performance. / text
|
4 |
Improving TCP performance over heterogeneous networks : The investigation and design of End to End techniques for improving TCP performance for transmission errors over heterogeneous data networks.Alnuem, M.A. January 2009 (has links)
Transmission Control Protocol (TCP) is considered one of the most important protocols
in the Internet. An important mechanism in TCP is the congestion control
mechanism which controls TCP sending rate and makes TCP react to congestion
signals. Nowadays in heterogeneous networks, TCP may work in networks with some
links that have lossy nature (wireless networks for example). TCP treats all packet
loss as if they were due to congestion. Consequently, when used in networks that
have lossy links, TCP reduces sending rate aggressively when there are transmission
(non-congestion) errors in an uncongested network.
One solution to the problem is to discriminate between errors; to deal with congestion
errors by reducing TCP sending rate and use other actions for transmission
errors. In this work we investigate the problem and propose a solution using an
end-to-end error discriminator. The error discriminator will improve the current
congestion window mechanism in TCP and decide when to cut and how much to
cut the congestion window.
We have identified three areas where TCP interacts with drops: congestion window
update mechanism, retransmission mechanism and timeout mechanism. All of
these mechanisms are part of the TCP congestion control mechanism. We propose
changes to each of these mechanisms in order to allow TCP to cope with transmission
errors. We propose a new TCP congestion window action (CWA) for transmission
errors by delaying the window cut decision until TCP receives all duplicate acknowledgments
for a given window of data (packets in flight). This will give TCP a clear
image about the number of drops from this window. The congestion window size is
then reduced only by number of dropped packets. Also, we propose a safety mechanism
to prevent this algorithm from causing congestion to the network by using
an extra congestion window threshold (tthresh) in order to save the safe area where
there are no drops of any kind. The second algorithm is a new retransmission action
to deal with multiple drops from the same window. This multiple drops action
(MDA) will prevent TCP from falling into consecutive timeout events by resending
all dropped packets from the same window. A third algorithm is used to calculate
a new back-off policy for TCP retransmission timeout based on the network¿s available
bandwidth. This new retransmission timeout action (RTA) helps relating the
length of the timeout event with current network conditions, especially with heavy
transmission error rates.
The three algorithms have been combined and incorporated into a delay based
error discriminator. The improvement of the new algorithm is measured along with
the impact on the network in terms of congestion drop rate, end-to-end delay, average
queue size and fairness of sharing the bottleneck bandwidth. The results show that
the proposed error discriminator along with the new actions toward transmission
errors has increased the performance of TCP. At the same time it has reduced the
load on the network compared to existing error discriminators. Also, the proposed
error discriminator has managed to deliver excellent fairness values for sharing the
bottleneck bandwidth.
Finally improvements to the basic error discriminator have been proposed by
using the multiple drops action (MDA) for both transmission and congestion errors.
The results showed improvements in the performance as well as decreases in the
congestion loss rates when compared to a similar error discriminator. / Ministry of Higher Education and
King Saud University in Saudi Arabia.
|
5 |
Improving TCP performance over satellite channelsAllman, Mark January 1997 (has links)
No description available.
|
6 |
PROTOCOL LAYERINGGrebe, David L. 10 1900 (has links)
International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / The advent of COTS based network-centric data systems brings a whole new vocabulary into the realm of instrumentation. The Communications and computer industries have developed networks to a high level and they continue to evolve. One of the basic techniques that has proven itself useful with this technology is the use of a “layered architecture.” This paper is an attempt to discuss the basic ideas behind this concept and to give some understanding of the vocabulary that has grown up with it.
|
7 |
Design and Analysis of a Novel Split and Aggregated Transmission Control Protocol for Smart Metering InfrastructureKhalifa, Tarek 21 May 2013 (has links)
Utility companies (electricity, gas, and water suppliers), governments, and
researchers recognize an urgent need to deploy communication-based systems to
automate data collection from smart meters and sensors, known as Smart Metering
Infrastructure (SMI) or Automatic Meter Reading (AMR). A smart metering system
is envisaged to bring tremendous benefits to customers, utilities, and
governments. The advantages include reducing peak demand for energy, supporting
the time-of-use concept for billing, enabling customers to make informed
decisions, and performing effective load management, to name a few.
A key element in an SMI is communications between meters and utility servers.
However, the mass deployment of metering devices in the grid calls for studying
the scalability of communication protocols. SMI is characterized by the
deployment of a large number of small Internet Protocol (IP) devices sending
small packets at a low rate to a central server. Although the individual
devices generate data at a low rate, the collective traffic produced is
significant and is disruptive to network communication functionality. This
research work focuses on the scalability of the transport layer
functionalities. The TCP congestion control mechanism, in particular, would be
ineffective for the traffic of smart meters because a large volume of data
comes from a large number of individual sources. This situation makes the TCP
congestion control mechanism unable to lower the transmission rate even when
congestion occurs. The consequences are a high loss rate for metered data and
degraded throughput for competing traffic in the smart metering network.
To enhance the performance of TCP in a smart metering infrastructure (SMI), we
introduce a novel TCP-based scheme, called Split- and Aggregated-TCP (SA-TCP).
This scheme is based on the idea of upgrading intermediate devices in SMI
(known in the industry as regional collectors) to offer the service of
aggregating the TCP connections. An SA-TCP aggregator collects data packets
from the smart meters of its region over separate TCP connections; then it
reliably forwards the data over another TCP connection to the utility server.
The proposed split and aggregated scheme provides a better response to traffic
conditions and, most importantly, makes the TCP congestion control and flow
control mechanisms effective. Supported by extensive ns-2 simulations, we show
the effectiveness of the SA-TCP approach to mitigating the problems in terms of
the throughput and packet loss rate performance metrics.
A full mathematical model of SA-TCP is provided. The model is highly accurate
and flexible in predicting the behaviour of the two stages, separately and
combined, of the SA-TCP scheme in terms of throughput, packet loss rate and
end-to-end delay. Considering the two stages of the scheme, the modelling
approach uses Markovian models to represent smart meters in the first stage and
SA-TCP aggregators in the second. Then, the approach studies the interaction of
smart meters and SA-TCP aggregators with the network by means of standard
queuing models. The ns-2 simulations validate the math model results.
A comprehensive performance analysis of the SA-TCP scheme is performed. It
studies the impact of varying various parameters on the scheme, including the
impact of network link capacity, buffering capacity of those RCs that act as
SA-TCP aggregators, propagation delay between the meters and the utility
server, and finally, the number of SA-TCP aggregators. The performance results
show that adjusting those parameters makes it possible to further enhance
congestion control in SMI. Therefore, this thesis also formulates an
optimization model to achieve better TCP performance and ensures satisfactory
performance results, such as a minimal loss rate and acceptable end-to-end
delay. The optimization model also considers minimizing the SA-TCP scheme
deployment cost by balancing the number of SA-TCP aggregators and the link
bandwidth, while still satisfying performance requirements.
|
8 |
Throughput Enhancement of TCP over Wireless LinksGupta, Pawan Kumar 01 1900 (has links)
The congestion control mechanisms of Transmission Control Protocol (TCP) are very effective in providing best effort service in wired networks, where packet losses are mainly due to congestion in the network. In wireless mobile networks, more often than not, loss of packets is because of corruption of data on the wireless link. The TCP sender responds to these losses as if they are due to congestion, by reducing its congestion window, thereby reducing the rate of flow of packets. The reduction in congestion window is a necessity when network is experiencing congestion to avoid congestion collapse but it is not required if packet losses occur due to corruption of data on the wireless link. This unnecessary reduction in congestion window for corruption losses is the main reason for poor throughput of data transfer in wireless networks. The reduction in congestion window for corruption losses can be avoided if TCP can successfully differentiate between packet losses due to congestion and corruption.
We suggest enhancements to TCP that, if implemented, will help the TCP receiver in separately identifying corruption losses and congestion losses. The enhancements are suggested over and above standard TCP NewReno and we call this new scheme as "NewRenoEln (NewReno with Explicit Loss Notification)". We suggest that the TCP sender attach a separate checksum for the TCP header with the packet. Since the length of the TCP header is much smaller as compared to the length of the TCP packet, there is a large probability that the TCP receiver will receive the header portion of the TCP packet without error even if the data portion of the packet is corrupted. Once the header information is found to be correct for a corrupted packet, the receiver can generate reliable Explicit 5oss Notification (ELN) for the sender.
We derive an expression for the probability of a receiver generating successful Explicit
Loss Notification, assuming a generic link layer protocol that is used for data transfer over wireless link. With this analysis, we show that there is large probability that receiver will generate successful ELN for various channel conditions We also suggest modifications to the sender behavior on receiving successful Explicit Loss Notification from the receiver. With these modifications, the TCP sender will recover from corruption losses without any reduction in congestion window.
There is also a need to develop a unified analytical approach for the evaluation of
TCP performance. We develop an analytical approach for the performance evaluation of
NewRenoEln scheme. We compare the throughput results obtained by analytical calculations with results obtained by simulation and find them to be very close to each other.
We also compare the performance of the proposed scheme NewRenoEln and the standard NewReno TCP via simulation as well as analytical approach, and find considerable improvement in throughput over wireless links.
|
9 |
Design and Analysis of a Novel Split and Aggregated Transmission Control Protocol for Smart Metering InfrastructureKhalifa, Tarek 21 May 2013 (has links)
Utility companies (electricity, gas, and water suppliers), governments, and
researchers recognize an urgent need to deploy communication-based systems to
automate data collection from smart meters and sensors, known as Smart Metering
Infrastructure (SMI) or Automatic Meter Reading (AMR). A smart metering system
is envisaged to bring tremendous benefits to customers, utilities, and
governments. The advantages include reducing peak demand for energy, supporting
the time-of-use concept for billing, enabling customers to make informed
decisions, and performing effective load management, to name a few.
A key element in an SMI is communications between meters and utility servers.
However, the mass deployment of metering devices in the grid calls for studying
the scalability of communication protocols. SMI is characterized by the
deployment of a large number of small Internet Protocol (IP) devices sending
small packets at a low rate to a central server. Although the individual
devices generate data at a low rate, the collective traffic produced is
significant and is disruptive to network communication functionality. This
research work focuses on the scalability of the transport layer
functionalities. The TCP congestion control mechanism, in particular, would be
ineffective for the traffic of smart meters because a large volume of data
comes from a large number of individual sources. This situation makes the TCP
congestion control mechanism unable to lower the transmission rate even when
congestion occurs. The consequences are a high loss rate for metered data and
degraded throughput for competing traffic in the smart metering network.
To enhance the performance of TCP in a smart metering infrastructure (SMI), we
introduce a novel TCP-based scheme, called Split- and Aggregated-TCP (SA-TCP).
This scheme is based on the idea of upgrading intermediate devices in SMI
(known in the industry as regional collectors) to offer the service of
aggregating the TCP connections. An SA-TCP aggregator collects data packets
from the smart meters of its region over separate TCP connections; then it
reliably forwards the data over another TCP connection to the utility server.
The proposed split and aggregated scheme provides a better response to traffic
conditions and, most importantly, makes the TCP congestion control and flow
control mechanisms effective. Supported by extensive ns-2 simulations, we show
the effectiveness of the SA-TCP approach to mitigating the problems in terms of
the throughput and packet loss rate performance metrics.
A full mathematical model of SA-TCP is provided. The model is highly accurate
and flexible in predicting the behaviour of the two stages, separately and
combined, of the SA-TCP scheme in terms of throughput, packet loss rate and
end-to-end delay. Considering the two stages of the scheme, the modelling
approach uses Markovian models to represent smart meters in the first stage and
SA-TCP aggregators in the second. Then, the approach studies the interaction of
smart meters and SA-TCP aggregators with the network by means of standard
queuing models. The ns-2 simulations validate the math model results.
A comprehensive performance analysis of the SA-TCP scheme is performed. It
studies the impact of varying various parameters on the scheme, including the
impact of network link capacity, buffering capacity of those RCs that act as
SA-TCP aggregators, propagation delay between the meters and the utility
server, and finally, the number of SA-TCP aggregators. The performance results
show that adjusting those parameters makes it possible to further enhance
congestion control in SMI. Therefore, this thesis also formulates an
optimization model to achieve better TCP performance and ensures satisfactory
performance results, such as a minimal loss rate and acceptable end-to-end
delay. The optimization model also considers minimizing the SA-TCP scheme
deployment cost by balancing the number of SA-TCP aggregators and the link
bandwidth, while still satisfying performance requirements.
|
10 |
Astronomy Software Integration with OpenSpaceBihi, Aniisa, Granström, Johanna January 2020 (has links)
This thesis aimed to create a messaging protocol for OpenSpace to interoperate with other astronomy software. The goal was to create a messaging standard that was not language-dependent and could be implemented by any astronomy software. To establish an asynchronous communication between OpenSpace and connected software, the Transmission Control Protocol (TCP), threading, and Peer-To-Peer (P2P) were the techniques mainly used. TCP was used to achieve reliable communication between software connected to the network. The enabling of two-way communication was solved by threading. P2P was used as a network communication architecture to share resources between the connected software. By using Unicode characters expressed through UTF-8, the Unicode Standard was used to encode messages sent. The messages are structured by combinations of different sizes of bytes and are sent and received as binary strings. All messages contain a header and the data being sent. Different message types were created to specify which type of data is sent. The protocol works primarily between OpenSpace and Glue but is not limited to these software. The implementation serves as the basis of the messaging protocol for OpenSpace, where Glue represents future software integrations.
|
Page generated in 0.0748 seconds