In the seven-layer OSI model of computer networking, media access control (MAC) data communication protocol is a sublayer of the data link layer (layer 2). The MAC sublayer provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multiple access network that incorporates a shared medium, e.g. an Ethernet network. The hardware that implements the MAC is referred to as a media access controller.
The MAC sublayer acts as an interface between the logical link control (LLC) sublayer and the network's physical layer. The MAC layer emulates a full-duplex logical communication channel in a multi-point network. This channel may provide unicast, multicast or broadcast communication service.
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.
Motivation for a specialized MAC (Hidden and exposed terminals, Near and far terminals), SDMA, FDMA, TDMA, CDMA, Wireless LAN/(IEEE 802.11)
Mobile Network Layer: IP and Mobile IP Network Layers, Packet Delivery and Handover Management, Location Management, Registration, Tunneling and Encapsulation, Route Optimization, DHCP
In the seven-layer OSI model of computer networking, media access control (MAC) data communication protocol is a sublayer of the data link layer (layer 2). The MAC sublayer provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multiple access network that incorporates a shared medium, e.g. an Ethernet network. The hardware that implements the MAC is referred to as a media access controller.
The MAC sublayer acts as an interface between the logical link control (LLC) sublayer and the network's physical layer. The MAC layer emulates a full-duplex logical communication channel in a multi-point network. This channel may provide unicast, multicast or broadcast communication service.
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.
Motivation for a specialized MAC (Hidden and exposed terminals, Near and far terminals), SDMA, FDMA, TDMA, CDMA, Wireless LAN/(IEEE 802.11)
Mobile Network Layer: IP and Mobile IP Network Layers, Packet Delivery and Handover Management, Location Management, Registration, Tunneling and Encapsulation, Route Optimization, DHCP
Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.
The most common wireless technologies use radio
IT6601 MOBILE COMPUTING UNITI
INTRODUCTION
Mobile Computing – Mobile Computing Vs wireless Networking – Mobile Computing Applications – Characteristics of Mobile computing – Structure of Mobile Computing Application. MAC Protocols – Wireless MAC Issues – Fixed Assignment Schemes – Random Assignment Schemes – Reservation Based Schemes.
Medium Access Control :-
1.Distributed Operation
2.Synchronization
3.Hidden Terminals
4.Exposed terminals
5.Throughput
6.Access delay
7.Fairness
8.Real-time Traffic support
9.Resource reservation
10.Ability to measure resource availability
11.Capability for power control
Adaptive rate control
Use of directional antennas
Message and Stream Oriented CommunicationDilum Bandara
Message and Stream Oriented Communication in distributed systems. Persistent vs. Transient Communication. Event queues, Pub/sub networks, MPI, Stream-based communication, Multicast communication
Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.
The most common wireless technologies use radio
IT6601 MOBILE COMPUTING UNITI
INTRODUCTION
Mobile Computing – Mobile Computing Vs wireless Networking – Mobile Computing Applications – Characteristics of Mobile computing – Structure of Mobile Computing Application. MAC Protocols – Wireless MAC Issues – Fixed Assignment Schemes – Random Assignment Schemes – Reservation Based Schemes.
Medium Access Control :-
1.Distributed Operation
2.Synchronization
3.Hidden Terminals
4.Exposed terminals
5.Throughput
6.Access delay
7.Fairness
8.Real-time Traffic support
9.Resource reservation
10.Ability to measure resource availability
11.Capability for power control
Adaptive rate control
Use of directional antennas
Message and Stream Oriented CommunicationDilum Bandara
Message and Stream Oriented Communication in distributed systems. Persistent vs. Transient Communication. Event queues, Pub/sub networks, MPI, Stream-based communication, Multicast communication
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
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.
AN EXPLICIT LOSS AND HANDOFF NOTIFICATION SCHEME IN TCP FOR CELLULAR MOBILE S...IJCNCJournal
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.
This slides will provide viewers a complete understanding of all the different virtualization techniques.
The main reference for the presentation is taken from Mastering cloud computing By Rajkumar Buyya.
presentation will make you aware about the programming techniques in shell , and will help you to build more strong foundation into the world of shell programming.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
Removing Uninteresting Bytes in Software FuzzingAftab Hussain
Imagine a world where software fuzzing, the process of mutating bytes in test seeds to uncover hidden and erroneous program behaviors, becomes faster and more effective. A lot depends on the initial seeds, which can significantly dictate the trajectory of a fuzzing campaign, particularly in terms of how long it takes to uncover interesting behaviour in your code. We introduce DIAR, a technique designed to speedup fuzzing campaigns by pinpointing and eliminating those uninteresting bytes in the seeds. Picture this: instead of wasting valuable resources on meaningless mutations in large, bloated seeds, DIAR removes the unnecessary bytes, streamlining the entire process.
In this work, we equipped AFL, a popular fuzzer, with DIAR and examined two critical Linux libraries -- Libxml's xmllint, a tool for parsing xml documents, and Binutil's readelf, an essential debugging and security analysis command-line tool used to display detailed information about ELF (Executable and Linkable Format). Our preliminary results show that AFL+DIAR does not only discover new paths more quickly but also achieves higher coverage overall. This work thus showcases how starting with lean and optimized seeds can lead to faster, more comprehensive fuzzing campaigns -- and DIAR helps you find such seeds.
- These are slides of the talk given at IEEE International Conference on Software Testing Verification and Validation Workshop, ICSTW 2022.
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
Communications Mining Series - Zero to Hero - Session 1DianaGray10
This session provides introduction to UiPath Communication Mining, importance and platform overview. You will acquire a good understand of the phases in Communication Mining as we go over the platform with you. Topics covered:
• Communication Mining Overview
• Why is it important?
• How can it help today’s business and the benefits
• Phases in Communication Mining
• Demo on Platform overview
• Q/A
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024Neo4j
Neha Bajwa, Vice President of Product Marketing, Neo4j
Join us as we explore breakthrough innovations enabled by interconnected data and AI. Discover firsthand how organizations use relationships in data to uncover contextual insights and solve our most pressing challenges – from optimizing supply chains, detecting fraud, and improving customer experiences to accelerating drug discoveries.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
Unlocking Productivity: Leveraging the Potential of Copilot in Microsoft 365, a presentation by Christoforos Vlachos, Senior Solutions Manager – Modern Workplace, Uni Systems
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...Neo4j
Leonard Jayamohan, Partner & Generative AI Lead, Deloitte
This keynote will reveal how Deloitte leverages Neo4j’s graph power for groundbreaking digital twin solutions, achieving a staggering 100x performance boost. Discover the essential role knowledge graphs play in successful generative AI implementations. Plus, get an exclusive look at an innovative Neo4j + Generative AI solution Deloitte is developing in-house.
Enchancing adoption of Open Source Libraries. A case study on Albumentations.AIVladimir Iglovikov, Ph.D.
Presented by Vladimir Iglovikov:
- https://www.linkedin.com/in/iglovikov/
- https://x.com/viglovikov
- https://www.instagram.com/ternaus/
This presentation delves into the journey of Albumentations.ai, a highly successful open-source library for data augmentation.
Created out of a necessity for superior performance in Kaggle competitions, Albumentations has grown to become a widely used tool among data scientists and machine learning practitioners.
This case study covers various aspects, including:
People: The contributors and community that have supported Albumentations.
Metrics: The success indicators such as downloads, daily active users, GitHub stars, and financial contributions.
Challenges: The hurdles in monetizing open-source projects and measuring user engagement.
Development Practices: Best practices for creating, maintaining, and scaling open-source libraries, including code hygiene, CI/CD, and fast iteration.
Community Building: Strategies for making adoption easy, iterating quickly, and fostering a vibrant, engaged community.
Marketing: Both online and offline marketing tactics, focusing on real, impactful interactions and collaborations.
Mental Health: Maintaining balance and not feeling pressured by user demands.
Key insights include the importance of automation, making the adoption process seamless, and leveraging offline interactions for marketing. The presentation also emphasizes the need for continuous small improvements and building a friendly, inclusive community that contributes to the project's growth.
Vladimir Iglovikov brings his extensive experience as a Kaggle Grandmaster, ex-Staff ML Engineer at Lyft, sharing valuable lessons and practical advice for anyone looking to enhance the adoption of their open-source projects.
Explore more about Albumentations and join the community at:
GitHub: https://github.com/albumentations-team/albumentations
Website: https://albumentations.ai/
LinkedIn: https://www.linkedin.com/company/100504475
Twitter: https://x.com/albumentations
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
In his public lecture, Christian Timmerer provides insights into the fascinating history of video streaming, starting from its humble beginnings before YouTube to the groundbreaking technologies that now dominate platforms like Netflix and ORF ON. Timmerer also presents provocative contributions of his own that have significantly influenced the industry. He concludes by looking at future challenges and invites the audience to join in a discussion.
Sudheer Mechineni, Head of Application Frameworks, Standard Chartered Bank
Discover how Standard Chartered Bank harnessed the power of Neo4j to transform complex data access challenges into a dynamic, scalable graph database solution. This keynote will cover their journey from initial adoption to deploying a fully automated, enterprise-grade causal cluster, highlighting key strategies for modelling organisational changes and ensuring robust disaster recovery. Learn how these innovations have not only enhanced Standard Chartered Bank’s data infrastructure but also positioned them as pioneers in the banking sector’s adoption of graph technology.
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.