Mobile transportlayer
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Mobile Transport Layer protocols aim to address challenges with TCP over mobile networks. Traditional TCP uses congestion control like slow start and fast retransmit/recovery that can reduce performance over mobile. Indirect TCP splits the connection at the access point to avoid wireless errors affecting the wired segment. Snooping TCP buffers packets at the access point and performs local retransmissions on errors. Mobile TCP splits the connection and uses an optimized TCP between the supervisory host and mobile host, choking the sender when the mobile is disconnected to avoid buffering large amounts of undelivered data.
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Mobile Network Layer protocols and mechanisms allow nodes to change their point of attachment to different networks while maintaining ongoing communication. Key concepts include:
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-One device should be able to work anywhere.
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- Maximum 2048Kbps
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- Indirect TCP splits the connection and handles losses locally at the base station. Snoop caches packets at the base station for retransmission.
- Mobile TCP further splits the connection and has the base station defer acknowledgments. It can also inform the sender about handoffs versus interface switches.
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-Worldwide devices need to have multiple technologies inside of them, i.e. tri-band phones, dual-mode phones
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The routing algorithm must deal with the following issues:
Correctness and simplicity: networks are never taken down; individual parts (e.g., links, routers) may fail, but the whole network should not.
Stability: if a link or router fails, how much time elapses before the remaining routers recognize the topology change? (Some never do..)
Fairness and optimality: an inherently intractable problem. Definition of optimality usually doesn't consider fairness. Do we want to maximize channel usage? Minimize average delay?
When we look at routing in detail, we'll consider both adaptive--those that take current traffic and topology into consideration--and nonadaptive algorithms.
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Proactive routing protocol
Each node maintain a routing table.
Sequence number is used to update the topology information
Update can be done based on event driven or periodic
Observations
May be energy expensive due to high mobility of the nodes
Delay can be minimized, as path to destination is already known to all nodes.
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Mobile computing (Wireless) Medium Access Control (MAC)
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3.Medium Access Control
Medium access control (MAC) is the sublayer of the data link layer that coordinates use of a shared medium in wireless networks. It addresses problems like hidden and exposed terminals through techniques like carrier sense multiple access (CSMA) and time division multiple access (TDMA). TDMA divides time into slots and assigns slots to different users to avoid collisions. Early random access protocols like Aloha and slotted Aloha had low throughput due to many collisions, while later protocols use RTS/CTS handshaking and carrier sensing to reduce collisions and improve throughput.
Snooping TCP
This document describes three TCP-aware link layer protocols: Snooping TCP, Wireless TCP, and Delayed DACK. Snooping TCP uses an agent at the base station to snoop and buffer TCP connections, ensuring packets are delivered to the mobile node in order and retransmitting lost packets. Wireless TCP modifies timestamps to compensate for increased round-trip time. Delayed DACK delays acknowledgments to allow time for lost packets to be recovered before triggering retransmissions.
Lecture 6
Medium access control methods from fixed networks like CSMA/CD may not work well for wireless networks due to signal strength degradation over distance and hidden and exposed terminal problems. Various MAC protocols were developed for wireless including TDMA, FDMA, polling, and random access methods like Aloha and its variants. Later protocols use signaling messages to reserve channels and avoid collisions, like MACA which uses RTS/CTS messages.
Unit 4
The document discusses various transport layer protocols for mobile computing environments:
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- Indirect TCP segments the TCP connection and uses a specialized TCP for the wireless link, isolating wireless errors. But it loses end-to-end semantics.
- Snooping TCP buffers packets near the mobile host and performs local retransmissions transparently. But wireless errors can still propagate to the server.
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Unit 2
The document discusses various medium access control (MAC) protocols for wireless networks. It describes challenges with applying carrier sense multiple access with collision detection (CSMA/CD) to wireless networks due to problems like hidden and exposed terminals. It then covers different MAC schemes like space division multiple access (SDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA) that aim to address these challenges. Specific protocols discussed in more detail include Aloha, slotted Aloha, and how TDMA can be used for fixed or dynamic channel allocation.
Mobile network layer (mobile comm.)
Mobile IP allows mobile nodes to change their point of attachment between IP networks while maintaining ongoing connections. It defines entities like mobile nodes, home agents, and foreign agents to facilitate IP packet delivery to the mobile node's current location. The key operations in Mobile IP are agent discovery, registration of the mobile node's new location with its home agent, and tunneling of packets from the home agent to the foreign agent or mobile node's care-of address.
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Similar to Mobile transportlayer
Mobile transport layer .
The document discusses several mechanisms used in TCP for mobile computing. It describes:
1) TCP congestion control mechanisms like slow-start and fast retransmit/fast recovery which are designed to address packet loss. However, these can be inappropriate for wireless networks where packet loss is often due to errors rather than congestion.
2) Approaches like Indirect TCP, Snooping TCP, and Mobile TCP which modify TCP for mobile networks by splitting connections or having a supervisory host monitor the connection to enable local retransmissions and avoid unnecessary window reductions when the mobile host disconnects.
3) Other TCP optimizations for mobile like forced fast retransmit after handovers and transmission timeout freezing to avoid slow-start
Cs8601 4
UNIT IV MOBILE TRANSPORT AND APPLICATION LAYER
Mobile TCP– WAP – Architecture – WDP – WTLS – WTP –WSP – WAE – WTA Architecture – WML
transport protocols
This document discusses challenges with TCP in mobile networks and various approaches to address them. It introduces indirect TCP, which splits the TCP connection to isolate the wireless link. Snooping TCP has the foreign agent snoop packets and acknowledgements to enable local retransmissions. Mobile TCP uses a supervisory host and window size adjustments to handle disconnections. Other optimizations discussed include forced fast retransmit after handovers, freezing TCP timers during disconnects, and selective retransmissions. The document compares the advantages and disadvantages of these different "mobile TCP" approaches.
Ch7-Transport_Protocols.ppt
This document discusses several proposals to modify TCP for use in mobile environments:
1. Indirect TCP splits the TCP connection to isolate the wireless link but loses end-to-end semantics.
2. Snooping TCP allows local retransmissions through buffering and "snooping" but does not fully isolate the wireless link.
3. Mobile TCP handles disconnections through a supervisory host but does not isolate wireless link losses.
4. Fast retransmit/recovery avoids the slow start algorithm after handovers but mixes network layers.
The approaches vary in their ability to isolate the wireless link, efficiency, and amount of modification required to TCP.
Mobile Transport layer
This document discusses various approaches to improving TCP performance over mobile networks. It describes Indirect TCP, Snooping TCP, Mobile TCP, optimizations like fast retransmit/recovery and transmission freezing, and transaction-oriented TCP. Each approach is summarized in terms of its key mechanisms, advantages, and disadvantages. Overall, the document evaluates different ways TCP has been adapted to better support mobility and address challenges like frequent disconnections, packet losses during handovers, and high bit error rates over wireless links.
Unit 4
This document discusses several approaches to improving TCP performance over mobile networks:
Traditional TCP uses slow start and congestion control mechanisms that reduce efficiency over mobile networks. Indirect TCP segments connections and uses a proxy to improve performance. Snooping TCP buffers packets to enable fast retransmissions without changing endpoints. Mobile TCP freezes the sender's window on disconnection to avoid unnecessary retransmissions. These methods aim to isolate wireless losses from congestion responses and enable fast recovery from errors and handovers.
Mobile transport layer
The document discusses various approaches to modifying TCP for use in mobile networks. Indirect TCP splits the TCP connection at the foreign agent, keeping the fixed network unchanged but losing end-to-end semantics. Snooping TCP has the foreign agent snoop packets and retransmit lost packets locally without changing TCP. Mobile TCP uses a supervisory host to monitor disconnections and choke senders. Other approaches include forced fast retransmit after handovers, freezing TCP timers during disconnects, selective retransmission of only lost packets, and transaction-oriented TCP to combine connection setup in fewer packets. Each approach has advantages like efficiency or compatibility but also disadvantages like overhead or non-transparency.
EC 6802 WIRELESS NETWORK_ BABU M_ unit 3 ,4 & 5 PPT
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
mobile_transport_layer (1).pptx
1) Standard TCP performs poorly over wireless networks due to packet loss from errors and mobility rather than congestion. This causes unnecessary slow starts and window reductions.
2) Early approaches like Indirect TCP, Snooping TCP, and Mobile TCP split or modify the TCP connection to isolate the wireless link but lose end-to-end semantics or require changes.
3) Later techniques like forced fast retransmit and selective acknowledgements improve efficiency without changing TCP but require cooperation between layers. Overall no single solution is optimal due to the need to maintain compatibility with fixed networks.
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.
Mc unit 4-jwfiles
The document discusses various approaches to improving TCP for mobile networks. It begins by describing traditional TCP and its mechanisms for congestion control and reliable data transmission. However, TCP was designed for fixed networks and faces challenges in mobile environments due to higher error rates, mobility-induced packet loss, and inefficient slow start behavior after losses. Several TCP improvements are then outlined, including Indirect TCP which segments connections and uses a proxy at the access point to isolate the wireless portion. This allows specialized TCP variants to be used for the wireless link without changing the fixed network. Finally, socket migration during handover is discussed to maintain connections as the mobile host moves.
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.
C10 transport protocols
The document discusses various approaches to improving TCP performance over mobile networks. Indirect TCP splits the TCP connection at the foreign agent to isolate the wireless link. Snooping TCP has the foreign agent buffer packets and retransmit lost packets locally. Mobile TCP uses a supervisory host to monitor connections and choke the sender window during disconnections. Other techniques discussed include fast retransmit/recovery after handovers, freezing TCP states during interruptions, selective retransmission of only lost packets, and transaction-oriented TCP to reduce overhead of short messages. Each approach has advantages but also disadvantages related to compatibility, transparency, and complexity.
Transport protocols
The document discusses various approaches to improving TCP performance over mobile networks, including:
1. Indirect TCP which splits the TCP connection to isolate errors on the wireless link. This requires no changes to fixed network hosts but loses end-to-end semantics.
2. Snooping TCP where the foreign agent buffers packets and retransmits lost packets transparently. This maintains end-to-end semantics but does not fully isolate the wireless link.
3. Mobile TCP which splits the connection and supports lengthy disconnections by freezing transmission at disconnected base stations. However, it propagates wireless losses into the fixed network.
Improving Performance of TCP in Wireless Environment using TCP-P
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.
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.
Raj
This document discusses transport layer protocols for ad hoc wireless networks. It first outlines the objectives of transport layer protocols, which include setting up end-to-end connections, delivering data packets reliably, and controlling flow and congestion. It then describes how traditional protocols like UDP and TCP are not suitable for wireless networks due to issues like frequent path breaks, network partitioning, and interference. The document proposes several approaches to improve transport layer performance in wireless networks, including splitting transport layer functions, using end-to-end approaches, and employing explicit link failure notification to handle breaks more efficiently. Key challenges for transport protocols in wireless ad hoc networks involve addressing mobility, interference and unreliable links.
AN EXPLICIT LOSS AND HANDOFF NOTIFICATION SCHEME IN TCP FOR CELLULAR MOBILE S...
With the proliferation of mobile and wireless computing devices, the demand for continuous network connectivity exits for various wired-and-wireless integrated networks. Since Transmission Control Protocol (TCP) is the standard network protocol for communication on the Interne, any wireless network with Internet service need to be compatible with TCP. TCP is tuned to perform well in traditional wired
networks, where packet losses occur mostly because of congestion. However cellular wireless network
suffers from significant losses due to high bit errors and mobile handoff. TCP responds to all losses by
invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance. This
paper presents an improved Explicit Loss Notification algorithm to distinguish between packet loss due to congestion and packet loss due to wireless errors and handoffs. Simulation results show that the proposed protocol significantly improves the performance of TCP over cellular wireless network in terms of throughput and congestion window dynamics.
unit-2 mc.pdf
This document summarizes key aspects of mobile computing and transport layer protocols for mobile networks. It begins with an overview of Mobile IP, including its components and how it works. Key mechanisms like agent discovery, registration, and tunneling are described. Improvements to TCP performance in mobile networks are also discussed, such as indirect TCP, snooping TCP, and selective retransmission. The document provides high-level explanations of these topics in under 3 sentences.
Similar to Mobile transportlayer (20)
Mobile Computing - Mobile Transport Layer.pptx.pdf
Mobile Computing - Mobile Transport Layer.pptx.pdf
EC 6802 WIRELESS NETWORK_ BABU M_ unit 3 ,4 & 5 PPT
EC 6802 WIRELESS NETWORK_ BABU M_ unit 3 ,4 & 5 PPT
Improving Performance of TCP in Wireless Environment using TCP-P
Improving Performance of TCP in Wireless Environment using TCP-P
AN EXPLICIT LOSS AND HANDOFF NOTIFICATION SCHEME IN TCP FOR CELLULAR MOBILE S...
AN EXPLICIT LOSS AND HANDOFF NOTIFICATION SCHEME IN TCP FOR CELLULAR MOBILE S...
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P4 foundation
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Navigating Post-Quantum Blockchain: Resilient Cryptography in Quantum Threats
In the rapidly evolving landscape of blockchain technology, the advent of quantum computing poses unprecedented challenges to traditional cryptographic methods. As quantum computing capabilities advance, the vulnerabilities of current cryptographic standards become increasingly apparent.
This presentation, "Navigating Post-Quantum Blockchain: Resilient Cryptography in Quantum Threats," explores the intersection of blockchain technology and quantum computing. It delves into the urgent need for resilient cryptographic solutions that can withstand the computational power of quantum adversaries.
Key topics covered include:
An overview of quantum computing and its implications for blockchain security.
Current cryptographic standards and their vulnerabilities in the face of quantum threats.
Emerging post-quantum cryptographic algorithms and their applicability to blockchain systems.
Case studies and real-world implications of quantum-resistant blockchain implementations.
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Join us as we navigate the complexities of securing blockchain networks in a quantum-enabled future. Gain insights into the latest advancements and best practices for safeguarding data integrity and privacy in the era of quantum threats.
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校名:学校英文全称
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毕业生姓名：这是最重要的信息之一，标志着该证书是由特定人员获得的。
颁发日期：这是毕业正式生效的时间，也代表着毕业生学业的结束。
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Have you noticed the OpenSSF Scorecard badges on the official Dart and Flutter repos? It's Google's way of showing that they care about security. Practices such as pinning dependencies, branch protection, required reviews, continuous integration tests etc. are measured to provide a score and accompanying badge.
You can do the same for your projects, and this presentation will show you how, with an emphasis on the unique challenges that come up when working with Dart and Flutter.
The session will provide a walkthrough of the steps involved in securing a first repository, and then what it takes to repeat that process across an organization with multiple repos. It will also look at the ongoing maintenance involved once scorecards have been implemented, and how aspects of that maintenance can be better automated to minimize toil.
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Triaging Issues with Automation:
This segment addresses how automation can be leveraged to intelligently triage and prioritize security issues. It will cover technologies and methodologies for automatically assessing the context and potential impact of vulnerabilities, facilitating quicker and more accurate decision-making. The use of automated alerting and reporting mechanisms to ensure the right stakeholders are informed in a timely manner will also be discussed.
Identifying Ownership Automatically:
Automating the process of identifying who owns the responsibility for fixing specific security issues is critical for efficient remediation. This part of the lecture will explore tools and practices for mapping vulnerabilities to code owners, leveraging version control and project management tools.
Three Tips to Scale the Shift Left Program:
Finally, the lecture will offer three practical tips for organizations looking to scale their Shift Left security programs. These will include recommendations on fostering a security culture within development teams, employing DevSecOps principles to integrate security throughout the development
Interaction Latency: Square's User-Centric Mobile Performance Metric
Mobile performance metrics often take inspiration from the backend world and measure resource usage (CPU usage, memory usage, etc) and workload durations (how long a piece of code takes to run).
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At Square, our customers spend most of their time in the app long after it's launched, and they don't scroll much, so app launch time and smoothness aren't critical metrics. What should we track instead?
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Mobile transportlayer
- 2. Introduction ● ● Mobility support on only lower layer is not enough to provide mobility support for applications. As application is directly communicates with transport Layer only.
- 3. Traditional TCP Congestion Control ● ● ● ● ● TCP designed for fixed n/w with fixed end-systems. Congestion may appear from time to time even in carefully designed networks. Sender notices the missing ACK for the lost packet and assumes a packet loss due to congestion. Retransmitting the missing packets , might only increase the congestion. Solution – TCP show down the transmission rate dramatically.
- 4. Traditional TCP Slow start ● ● Sender always calculates a congestion window for a receiver. The start size of the congestion window is one segment. ● Double the window size after receiving ACK. ● Maintain the congestion threshold.
- 5. Traditional TCP Fast retransmit/fast recovery ● Two things lead to a reduction of the congestion threshold :– Fast retransmit – continious receving of ACK for the same packet. – Fast recovery – receipt of ACK shows that there is no congestion to justify slow start. The sender perform fast recovery from the packet loss.
- 6. Implication on mobility ● Slow start is not a solution in case of mobility ● The reason for this is of using wrong assumptions. ● ● ● ● Error rate on wireless links are higher as compare to wired links. Retransmittion may increase duplicates at layer 2 and more connection are end-to-end encryption. Mobility itself cause packet loss. TCP detects missing ACK via time-outs and concluding packet loss due to congestion control only.
- 7. Classical TCP improvements Indirect TCP ● ● I-TCP segments a TCP connection into a fixed part and a wireless part. Standard TCP is used between the fixed computer and the access point/FA. ● Now access point/FA terminates the standard TCP connection. ● It means access point/FA now seen as the mobile host for the fixed host. ● Access point/FA work as a proxy. ● ● If the packet is lost on the wireless link, the mobile hosts notice this much faster due to much lower RTT. In case of handover , AP/FA act as a proxy buffering packets for retransmission after the handover to the new AP/FA.
- 8. Advantages of I-TCP ● ● ● ● Does not require any change in the TCP protocol. Due to strict partitioning into two connections, transmission error on wireless link cannot propogate into the fixed network. Short delay between mobile node and AP/FA, independent of other traffice streams. Partitioning of two connection allow us to use different TCP.
- 9. Disadvantages of I-TCP ● ● ● Loss of end-to-end functionality of TCP. If sender receive the ACK it means AP/FA receive the packet. Foreign agent must be a trusted entity
- 10. Snooping TCP ● ● ● ● ● This method based on end-to-end TCP semantic. Objective – is to buffer data close to the mobile host to perform fast local retransmission in cse of packet loss. FA/AP buffers all packets with destination mobile host and additionally 'snoop' the packet flow in both directions. FA not ACK data to the corresponent host. FA/AP will retransmits the packet to mobile host directly form the buffer.
- 11. Snooping TCP ● Data transfer from the mobile host with destination correspondent host – FA snoops into packet stream to detect gaps in the seq. no. of TCP. – If FA detect missing packet, – then , it return a NACK to the mobile host. – Now mobile host retransmit the missing packet immediately.
- 12. Advantage/Disadvantage of Snooping TCP ● Advantage – – ● End-to-End TCP semantic is preserved. Need no modification on FA/AP and correspondent node Disadvantage – It takes some time until the FA/AP can successfully retransmit a packet from its buffer due to problem in wireless link. – Have to manage time-out at FA/AP and correspondent Node – If sender using end-to-end encryption scheme then TCP protocol header will be encrypted – this approach will not work.
- 13. Mobile TCP ● ● ● Dropping of packets due to a handover or higher bit error rate is not the only problem occurs. The occurence of lengthy and/or frequent disconnections in another problem. I-TCP when mobile disconnected:– ● Has to buffer more and more data – need more buffer. Snooping TCP when mobile disconnected:– Mobile will not able to send ACK.
- 14. Working of Mobile TCP ● ● ● ● It splits the TCP connection into two parts as ITCP An unchanged TCP is used between HostSupervisory Host while an optimized TCP is used on the SH-MH connection. Assumption – M-TCP assumes low bit error rate on wireless link. M-TCP does not perform caching/retransmission of data.
- 15. Working of Mobile TCP (Cont.) ● ● ● ● SH monitors all packets sent to the MH and ACKs returned from the MH. If the SH does not receive an ACK for some time , it assumes that the MH is disconnected. It chokes the sender by setting the sender's windows size 0. It means sender will not retrasmit data.