UNIT II DATA-LINK LAYER & MEDIA ACCESS Introduction – Link-Layer
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Data Communication and Computer Network Unit 1
Department of Collegiate Education GOVERNMENT FIRST GRADE COLLEGE RAIBAG-591317 Department of Computer Science Lecture Notes SUBJECT : DATA COMMUNICATIONS AND COMPUTER NETWORKS SUBJECT CODE : 17BScCST61 CLASS : BSC VI Sem Paper-1 Subject In charge Smt Bhagirathi Halalli Assistant Professor 2019-20 Data Communication and Computer Network Unit 1 Unit 1: Introduction Content: 1.1. Data communications, 1.2. Networks, 1.3. The internet, 1.4. Protocols and standards, 1.5. Network models – OSI model, 1.6. TCP/IP protocol suite, 1.7. Addressing. 1.1.Data Communications, Data refers to the raw facts that are collected while information refers to processed data that enables us to take decisions. Ex. When result of a particular test is declared it contains data of all students, when you find the marks you have scored you have the information that lets you know whether you have passed or failed. The word data refers to any information which is presented in a form that is agreed and accepted upon by is creators and users. Data Communication Data Communication is a process of exchanging data or information In case of computer networks this exchange is done between two devices over a transmission medium. This process involves a communication system which is made up of hardware and software. The hardware part involves the sender and receiver devices and the intermediate devices through which the data passes. The software part involves certain rules which specify what is to be communicated, how it is to be communicated and when. It is also called as a Protocol. The following sections describe the fundamental characteristics that are important for the effective working of data communication process and are followed by the components that make up a data communications system. -
The OSI Model
Data Encapsulation & OSI & TCP/IP Models Week 2 Lecturer: Lucy White [email protected] Office : 324 1 Network Protocols • A protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate. Protocols determine the format, timing, sequencing, flow control and error control in data communication. Without protocols, the computer cannot make or rebuild the stream of incoming bits from another computer into the original format. • Protocols control all aspects of data communication, which include the following: - How the physical network is built - How computers connect to the network - How the data is formatted for transmission - The setting up and termination of data transfer sessions - How that data is sent - How to deal with errors 2 Protocol Suites & Industry Standard • Many of the protocols that comprise a protocol suite reference other widely utilized protocols or industry standards • Institute of Electrical and Electronics Engineers (IEEE) or the Internet Engineering Task Force (IETF) • The use of standards in developing and implementing protocols ensures that products from different manufacturers can work together for efficient communications 3 Function of Protocol in Network Communication A standard is a process or protocol that has been endorsed by the networking industry and ratified by a standards organization 4 Protocol Suites TCP/IP Protocol Suite and Communication Function of Protocol in Network Communication 6 Function of Protocol in Network Communication • Technology independent Protocols -Many diverse types of devices can communicate using the same sets of protocols. This is because protocols specify network functionality, not the underlying technology to support this functionality. -
Solutions to Chapter 2
CS413 Computer Networks ASN 4 Solutions Solutions to Assignment #4 3. What difference does it make to the network layer if the underlying data link layer provides a connection-oriented service versus a connectionless service? [4 marks] Solution: If the data link layer provides a connection-oriented service to the network layer, then the network layer must precede all transfer of information with a connection setup procedure (2). If the connection-oriented service includes assurances that frames of information are transferred correctly and in sequence by the data link layer, the network layer can then assume that the packets it sends to its neighbor traverse an error-free pipe. On the other hand, if the data link layer is connectionless, then each frame is sent independently through the data link, probably in unconfirmed manner (without acknowledgments or retransmissions). In this case the network layer cannot make assumptions about the sequencing or correctness of the packets it exchanges with its neighbors (2). The Ethernet local area network provides an example of connectionless transfer of data link frames. The transfer of frames using "Type 2" service in Logical Link Control (discussed in Chapter 6) provides a connection-oriented data link control example. 4. Suppose transmission channels become virtually error-free. Is the data link layer still needed? [2 marks – 1 for the answer and 1 for explanation] Solution: The data link layer is still needed(1) for framing the data and for flow control over the transmission channel. In a multiple access medium such as a LAN, the data link layer is required to coordinate access to the shared medium among the multiple users (1). -
Logical Link Control and Channel Scheduling for Multichannel Underwater Sensor Networks
ICST Transactions on Mobile Communications and Applications Research Article Logical Link Control and Channel Scheduling for Multichannel Underwater Sensor Networks Jun Li ∗, Mylene` Toulgoat, Yifeng Zhou, and Louise Lamont Communications Research Centre Canada, 3701 Carling Avenue, Ottawa, ON. K2H 8S2 Canada Abstract With recent developments in terrestrial wireless networks and advances in acoustic communications, multichannel technologies have been proposed to be used in underwater networks to increase data transmission rate over bandwidth-limited underwater channels. Due to high bit error rates in underwater networks, an efficient error control technique is critical in the logical link control (LLC) sublayer to establish reliable data communications over intrinsically unreliable underwater channels. In this paper, we propose a novel protocol stack architecture featuring cross-layer design of LLC sublayer and more efficient packet- to-channel scheduling for multichannel underwater sensor networks. In the proposed stack architecture, a selective-repeat automatic repeat request (SR-ARQ) based error control protocol is combined with a dynamic channel scheduling policy at the LLC sublayer. The dynamic channel scheduling policy uses the channel state information provided via cross-layer design. It is demonstrated that the proposed protocol stack architecture leads to more efficient transmission of multiple packets over parallel channels. Simulation studies are conducted to evaluate the packet delay performance of the proposed cross-layer protocol stack architecture with two different scheduling policies: the proposed dynamic channel scheduling and a static channel scheduling. Simulation results show that the dynamic channel scheduling used in the cross-layer protocol stack outperforms the static channel scheduling. It is observed that, when the dynamic channel scheduling is used, the number of parallel channels has only an insignificant impact on the average packet delay. -
Communications
The Essentials of Datalink Communications The origins and course of Air-to-Ground Messaging The Essentials of Datalink Communications Contents international Trip Support | international Trip The Technology that HR Created 02 Inmarsat Satellite 06 Growing into an Operational Necessity 03 Iridium Satellite 07 UAS Communications Mechanisms 04 Upcoming Regulations 10 VHF Radio 05 The Future of ACARS 11 © Copyright 2016 Page 1/12 The Technology that HR Created t one time in the not-so-distant past, pilots and other ARINC’s solution was an automated system, called the A flight crew members were paid different rates for the ARINC Communications Addressing and Reporting System, time they were airborne versus the time they were performing or ACARS for short, which sent short text data from the ground operations. Events like aircraft pushback, taxi, takeoff, avionics of the aircraft directly to the ground-based entities landing, and gate arrival were transmitted via voice over radio through Very High Frequency (VHF) radio frequencies frequencies to operators who would relay this information back without any crewmember involvement. The aircraft was to the airlines. The pilots were responsible for self-reporting programmed to take advantage of switches and automation their own times and movements. Understanding that people points on the aircraft, resulting in the creation of a set of can sometimes be forgetful, or worse, willfully manipulative, messages referred to as the OOOI report. An OOOI report is the major airlines began searching for a solution that tracked any of four messages: Out, Off, On and In. Still in wide-scale crewmember pay in a more structured and accurate way. -
Data Networks
Second Ed ition Data Networks DIMITRI BERTSEKAS Massachusetts Institute of Technology ROBERT GALLAGER Massachusetts Institute ofTechnology PRENTICE HALL, Englewood Cliffs, New Jersey 07632 2 Node A Node B Time at B --------- Packet 0 Point-to-Point Protocols and Links 2.1 INTRODUCTION This chapter first provides an introduction to the physical communication links that constitute the building blocks of data networks. The major focus of the chapter is then data link control (i.e., the point-to-point protocols needed to control the passage of data over a communication link). Finally, a number of point-to-point protocols at the network, transport, and physical layers are discussed. There are many similarities between the point-to-point protocols at these different layers, and it is desirable to discuss them together before addressing the more complex network-wide protocols for routing, flow control, and multiaccess control. The treatment of physical links in Section 2.2 is a brief introduction to a very large topic. The reason for the brevity is not that the subject lacks importance or inherent interest, but rather, that a thorough understanding requires a background in linear system theory, random processes, and modem communication theory. In this section we pro vide a sufficient overview for those lacking this background and provide a review and perspective for those with more background. 37 38 Point-to-Point Protocols and Links Chap. 2 In dealing with the physical layer in Section 2.2, we discuss both the actual com munication channels used by the network and whatever interface modules are required at the ends of the channels to transmit and receive digital data (see Fig 2.1). -
Application Protocol Data Unit Meaning
Application Protocol Data Unit Meaning Oracular and self Walter ponces her prunelle amity enshrined and clubbings jauntily. Uniformed and flattering Wait often uniting some instinct up-country or allows injuriously. Pixilated and trichitic Stanleigh always strum hurtlessly and unstepping his extensity. NXP SE05x T1 Over I2C Specification NXP Semiconductors. The session layer provides the mechanism for opening closing and managing a session between end-user application processes ie a semi-permanent dialogue. Uses MAC addresses to connect devices and define permissions to leather and commit data 1. What are Layer 7 in networking? What eating the application protocols? Application Level Protocols Department of Computer Science. The present invention pertains to the convert of Protocol Data Unit PDU session. Network protocols often stay to transport large chunks of physician which are layer in. The term packet denotes an information unit whose box and tranquil is remote network-layer entity. What is application level security? What does APDU stand or Hop sound to rot the meaning of APDU The Acronym AbbreviationSlang APDU means application-layer protocol data system by. In the context of smart cards an application protocol data unit APDU is the communication unit or a bin card reader and a smart all The structure of the APDU is defined by ISOIEC 716-4 Organization. Application level security is also known target end-to-end security or message level security. PDU Protocol Data Unit Definition TechTerms. TCPIP vs OSI What's the Difference Between his Two Models. The OSI Model Cengage. As an APDU Application Protocol Data Unit which omit the communication unit advance a. -
Radio Communications in the Digital Age
Radio Communications In the Digital Age Volume 1 HF TECHNOLOGY Edition 2 First Edition: September 1996 Second Edition: October 2005 © Harris Corporation 2005 All rights reserved Library of Congress Catalog Card Number: 96-94476 Harris Corporation, RF Communications Division Radio Communications in the Digital Age Volume One: HF Technology, Edition 2 Printed in USA © 10/05 R.O. 10K B1006A All Harris RF Communications products and systems included herein are registered trademarks of the Harris Corporation. TABLE OF CONTENTS INTRODUCTION...............................................................................1 CHAPTER 1 PRINCIPLES OF RADIO COMMUNICATIONS .....................................6 CHAPTER 2 THE IONOSPHERE AND HF RADIO PROPAGATION..........................16 CHAPTER 3 ELEMENTS IN AN HF RADIO ..........................................................24 CHAPTER 4 NOISE AND INTERFERENCE............................................................36 CHAPTER 5 HF MODEMS .................................................................................40 CHAPTER 6 AUTOMATIC LINK ESTABLISHMENT (ALE) TECHNOLOGY...............48 CHAPTER 7 DIGITAL VOICE ..............................................................................55 CHAPTER 8 DATA SYSTEMS .............................................................................59 CHAPTER 9 SECURING COMMUNICATIONS.....................................................71 CHAPTER 10 FUTURE DIRECTIONS .....................................................................77 APPENDIX A STANDARDS -
Data Link Layer
Data link layer Goals: ❒ Principles behind data link layer services ❍ Error detection, correction ❍ Sharing a broadcast channel: Multiple access ❍ Link layer addressing ❍ Reliable data transfer, flow control: Done! ❒ Example link layer technology: Ethernet Link layer services Framing and link access ❍ Encapsulate datagram: Frame adds header, trailer ❍ Channel access – if shared medium ❍ Frame headers use ‘physical addresses’ = “MAC” to identify source and destination • Different from IP address! Reliable delivery (between adjacent nodes) ❍ Seldom used on low bit error links (fiber optic, co-axial cable and some twisted pairs) ❍ Sometimes used on high error rate links (e.g., wireless links) Link layer services (2.) Flow Control ❍ Pacing between sending and receiving nodes Error Detection ❍ Errors are caused by signal attenuation and noise. ❍ Receiver detects presence of errors signals sender for retrans. or drops frame Error Correction ❍ Receiver identifies and corrects bit error(s) without resorting to retransmission Half-duplex and full-duplex ❍ With half duplex, nodes at both ends of link can transmit, but not at same time Multiple access links / protocols Two types of “links”: ❒ Point-to-point ❍ PPP for dial-up access ❍ Point-to-point link between Ethernet switch and host ❒ Broadcast (shared wire or medium) ❍ Traditional Ethernet ❍ Upstream HFC ❍ 802.11 wireless LAN MAC protocols: Three broad classes ❒ Channel Partitioning ❍ Divide channel into smaller “pieces” (time slots, frequency) ❍ Allocate piece to node for exclusive use ❒ Random -
Draft Stable Implementation Agreement for Open
NBS PUBLICATIONS U.S. DEPARTMENT OF COMMERCE National Bureau of Standards Institute for Computer Sciences and Technology A 11 IDE 7 E T M NBSIR 87-3674 Draft Stable Implementation Agreements for Open Systems Interconnection Protocols NBS Workshop for Implementors of Open Systems Interconnection Version 1 Edition 0 October 1987 DRAFT STABLE IMPLEMENTATION AGREEMENTS Based on the Proceeding of the NBS/OSI Implementor’s Workshop Plenary Assembly Held October 9, 1987 National Bureau of Standards Gaithersburg, MD 20899 U.S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS — QC 100 - U 5 6 87-3674 1987 C • 2 U.S. DEPARTMENT OF COMMERCE National Bureau of Standards Institute for Computer Sciences and Technology Research Information Center NBSIR 87-3674 National r>ureau of Standards Gaithersburg, Maryland 20899 A) BSc DRAFT STABLE IMPLEMENTATION QCtoo AGREEMENTS FOR OPEN SYSTEMS < USy INTERCONNECTION PROTOCOLS m., 1921 c.> NBS Workshop for Implementors of Open Systems Interconnection Version 1 Edition 0 October 1987 DRAFT STABLE IMPLEMENTATION AGREEMENTS Based on the Proceeding of the NBS/OSI Implementor’s Workshop Plenary Assembly Held October 9, 1987 National Bureau of Standards Gaithersburg, MD 20899 U.S. DEPARTMENT OF COMMERCE, C. William Verity, Acting Secretary NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director 21 Table of Contents 1. GENERAL INFORMATION 1 1.1 PURPOSE OF THIS DOCUMENT * 1 1.2 PURPOSE OF THE WORKSHOP 1 1.3 WORKSHOP ORGANIZATION 1 2. SUB NETWORKS 1 2.1 LOCAL AREA NETWORKS 1 2.1.1 IEEE 802.2 LOGICAL LINK CONTROL 1 2.1.2 IEEE 802.3 CSMA/CD ACCESS METHOD 1 2.1.3 IEEE 802.4 TOKEN BUS ACCESS METHOD 1 2.1.4 IEEE 802.5 Token Ring Access Method 3 2.2 WIDE AREA NETWORKS 4 2.2.1 CCITT RECOMMENDATION X.25 4 2.3 PRIVATE SUBNETWORKS 4 2.3.1 PRIVATE SUBNETWORKS' 4 3. -
OSI Data Link Layer
OSI Data Link Layer Network Fundamentals – Chapter 7 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 1 Objectives Explain the role of Data Link layer protocols in data transmission. Describe how the Data Link layer prepares data for transmission on network media. Describe the different types of media access control methods. Identify several common logical network topologies and describe how the logical topology determines the media access control method for that network. Explain the purpose of encapsulating packets into frames to facilitate media access. Describe the Layer 2 frame structure and identify generic fields. Explain the role of key frame header and trailer fields including addressing, QoS, type of protocol and Frame Check Sequence. © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 2 Data Link Layer – Accessing the Media Describe the service the Data Link Layer provides as it prepares communication for transmission on specific media © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 3 Data Link Layer – Accessing the Media Describe why Data Link layer protocols are required to control media access © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 4 Data Link Layer – Accessing the Media Describe the role of framing in preparing a packet for transmission on a given media © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 5 Data Link Layer – Accessing the Media Describe the role the Data Link layer plays in linking the software and hardware layers © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 6 Data Link Layer – Accessing the Media Identify several sources for the protocols and standards used by the Data Link layer © 2007 Cisco Systems, Inc. -
Introduction to Spanning Tree Protocol by George Thomas, Contemporary Controls
Volume6•Issue5 SEPTEMBER–OCTOBER 2005 © 2005 Contemporary Control Systems, Inc. Introduction to Spanning Tree Protocol By George Thomas, Contemporary Controls Introduction powered and its memory cleared (Bridge 2 will be added later). In an industrial automation application that relies heavily Station 1 sends a message to on the health of the Ethernet network that attaches all the station 11 followed by Station 2 controllers and computers together, a concern exists about sending a message to Station 11. what would happen if the network fails? Since cable failure is These messages will traverse the the most likely mishap, cable redundancy is suggested by bridge from one LAN to the configuring the network in either a ring or by carrying parallel other. This process is called branches. If one of the segments is lost, then communication “relaying” or “forwarding.” The will continue down a parallel path or around the unbroken database in the bridge will note portion of the ring. The problem with these approaches is the source addresses of Stations that Ethernet supports neither of these topologies without 1 and 2 as arriving on Port A. This special equipment. However, this issue is addressed in an process is called “learning.” When IEEE standard numbered 802.1D that covers bridges, and in Station 11 responds to either this standard the concept of the Spanning Tree Protocol Station 1 or 2, the database will (STP) is introduced. note that Station 11 is on Port B. IEEE 802.1D If Station 1 sends a message to Figure 1. The addition of Station 2, the bridge will do ANSI/IEEE Std 802.1D, 1998 edition addresses the Bridge 2 creates a loop.