© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Data Link Layer Dr. Muazzam A. Khan.

Slides:



Advertisements
Similar presentations
1 Data Link Protocols Relates to Lab 2. This module covers data link layer issues, such as local area networks (LANs) and point-to-point links, Ethernet,
Advertisements

Network Fundamentals – Chapter 7 Sandra Coleman, CCNA, CCAI
Layer 1 of the TCP/IP protocol stack: Network Access Layer (NAL). Functions, performed on the layer. МАС address in Ethernet networks. Layer 1 of the TCP/IP.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 OSI Data Link Layer Network Fundamentals – Chapter 7.
Chapter 7 Data Link Layer
© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE I Chapter 6 1 Data Link Layer Network Fundamentals – Chapter 7 Modified by Tony Chen 01/30/2009.
Network Fundamentals – Chapter 7
© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 Chapter 5: Ethernet Introduction to Networks.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Communicating over the Network Network Fundamentals – Chapter 2.
Chapter 7- Data Link Layer
1 Chapter 9 Computer Networks. 2 Chapter Topics OSI network layers Network Topology Media access control Addressing and routing Network hardware Network.
CCNA 1 v3.1 Module 6 Review. 2 What 3 things happen on an Ethernet network after a collision occurs? A backoff algorithm is invoked and transmission is.
TDC /502, Summer II Unit 2: Underlying Technologies Transmission media (Section 3.1. Read on your own) Local Area Networks (LANs) –Ethernet.
OSI Model.
Understanding Networks. Objectives Compare client and network operating systems Learn about local area network technologies, including Ethernet, Token.
OSI Data Link Layer Network Fundamentals Chapter 7.
Module 6 Chapter 5. Ethernet Ethernet is now the dominant LAN technology in the world. Ethernet is not one technology but a family of LAN technologies.
The Saigon CTT Semester 1 CHAPTER 6. The Saigon CTT  Content LAN Standards. Hexadecimal Numbers. MAC Addressing. Framing. Media Access Control (MAC).
COMPUTER NETWORKS.
The OSI Model A layered framework for the design of network systems that allows communication across all types of computer systems regardless of their.
 The Open Systems Interconnection model (OSI model) is a product of the Open Systems Interconnection effort at the International Organization for Standardization.
Presentation_ID 1 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Chapter 4: Network Access.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Communicating over the Network Network Fundamentals – Chapter 2.
© Wiley Inc All Rights Reserved. CCNA: Cisco Certified Network Associate Study Guide CHAPTER 1: Internetworking.
1 Computer Networks Course: CIS 3003 Fundamental of Information Technology.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 OSI Data Link Layer Network Fundamentals – Chapter 7.
Chapter Five Network Architecture. Chapter Objectives  Describe the basic and hybrid LAN technologies  Describe a variety of enterprise-wide and WAN.
Chapter 2 The Infrastructure. Copyright © 2003, Addison Wesley Understand the structure & elements As a business student, it is important that you understand.
Lecture 2 TCP/IP Protocol Suite Reference: TCP/IP Protocol Suite, 4 th Edition (chapter 2) 1.
Wired LANs: Ethernet In Chapter 1, we learned that a local area network (LAN) is a computer network that is designed for a limited geographic area such.
ACM 511 Chapter 2. Communication Communicating the Messages The best approach is to divide the data into smaller, more manageable pieces to send over.
© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 Chapter 5: Ethernet Introduction to Networks.
Copyright CCNA 1 Chapter 5 Ethernet Fundamentals By Your Name.
1 Layer 2: Concepts Honolulu Community College Cisco Academy Training Center Semester 1 Version
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 OSI Data Link Layer Network Fundamentals – Chapter 7.
Ethernet Fundamentals. The success of Ethernet is due to the following factors: Simplicity and ease of maintenance Ability to incorporate new technologies.
Access to Shared Media - Media Access Control protocols RD-CSY10171.
Local Area Networks: Ethernet. IEEE Background Institution of Electrical and Electronic Engineering (IEEE) A professional non-profit organization Project.
Jaringan Komputer Dasar Data Link Layer (2) Aurelio Rahmadian.
 LANs – A Definition - A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings,
Objectives  Explain the role of Data Link layer protocols in data transmission.  Describe how the Data Link layer prepares data for transmission on.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Ethernet Network Fundamentals – Chapter 9.
Chapter Six The Data Link Layer. Objectives Learn about physical addressing on the network. Explore the MAC and LLC sublayers of Data Link. Get introduced.
Chapter 6 – Layer 2 MAC, Frames, Hex, etc.. Layer 1 / Layer 2 Layer 1 Signals, media, bit streams Layer 2 –Communicates with upper layers using Logical.
The Saigon CTT Semester 1 CHAPTER 6 Le Chi Trung.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 OSI Data Link Layer Network Fundamentals – Chapter 7.
Open System Interconnection Describe how information from a software application in one computer moves through a network medium to a software application.
Ethernet Overview it the IEEE standard for Ethernet.
Data Link Layer and Ethernet COM211 Communications and Networks CDA College Theodoros Christophides
IEEE 802.X Standards The Institute of Electrical and Electronics Engineers (IEEE) has developed a series of networking standards to ensure that networking.
01_NF_Ch07 - Data Link Layer ( 資料鏈結層 ) Modified from KC Khor, Multimedia Univ. Cyberjaya (KT Lo)
Chapter 7 OSI Data Link Layer.
CCNA3 Module 4 Brierley Module 4. CCNA3 Module 4 Brierley Topics LAN congestion and its effect on network performance Advantages of LAN segmentation in.
2016/3/11 1 Data Link Layer. 2016/3/11 2 Two basic services of Data Link Allows the upper layers to access the media using techniques such as framing.
+ Lecture#2: Ethernet Asma ALOsaimi. + Objectives In this chapter, you will learn to: Describe the operation of the Ethernet sublayers. Identify the major.
Data Link Protocols Relates to Lab 2.
Welcome Back Cisco Semester 1 & 2 Review. Why are Networks Complex Environments?? They involve: They involve: –Interconnections to networks outside an.
© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 1 OSI data link layer CCNA Exploration Semester 1 Chapter 7.
Cisco I Introduction to Networks Semester 1 Chapter 4 JEOPADY.
Jaringan Komputer_D3 TT
Introduction to Networks v6.0
Data Link Layer Dr. Muazzam A. Khan.
Ct1403 Lecture#2: DATA LINK LAYER
Ethernet and Token Ring LAN Networks
Chapter 3: Open Systems Interconnection (OSI) Model
Network Fundamentals – Chapter 7
CCNA 1 Chapter 5 Ethernet Fundamentals
Data Link Layer 2019/2/19.
Ethernet and Token Ring LAN Networks
LEARNING COMPUTER NETWORKS OSI Model (layers). Why a layered model?  Easier to teach communication process.  Speeds development, changes in one layer.
Presentation transcript:

© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Data Link Layer Dr. Muazzam A. Khan

2 Objectives  Explain the role of Data Link layer protocols in data transmission.  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  Explain the role of key frame header and trailer fields

3 Review of OSI Layers…  Application Layer: Provides the interface to the user  Transport Layer: Responsible for dividing and managing communications between the processes running in the two end systems  Network Layer: Protocols organize communication data so that it can travel across internetworks from the originating host to a destination host  Data Link Layer: Prepares Network layer packets for transmission and controls access to the physical media (focus of this chapter)

4 Data Link Layer Terms

5 Data Link Layer Services Two basic services:  Allows the upper layers to access the media using techniques such as framing  Controls how data is placed onto the media and is received from the media using techniques such as media access control and error detection

6 Data Link Layer Protocols  Data Link layer protocols are required to control access to the media

7 Media Access Control  The technique used for getting the frame on and off media is called the media access control method.

8 The Data-Link PDU - Frames  The Data Link layer prepares a packet for transport across the local media by encapsulating it with a header and a trailer to create a frame  The Data Link layer frame includes: Data - The packet from the Network layer Header - Contains control information, such as addressing, and is located at the beginning of the PDU Trailer - Contains control information added to the end of the PDU

9 Formatting Data for Transmission More on frame fields later…

10 Data Link Layer – Hardware & Software Layers  The Data Link layer connects upper layer services to the media The NIC (Network Interface Card) connects the PC to the media

11 Data Link Sublayers- LLC & MAC

12 Data Link Layer – Protocols & Standards  Protocols and standards used by the Data Link layer… International Organization for Standardization Institute of Electrical and Electronics Engineers American National Standards Institute International Telecommunication Union

13 More on Media Access Control - Regulating the placement of data frames onto the media

14 Controlled Access in a Shared Media Environment A closer look at this later… AKA deterministic

15 Contention-based Access in a Shared Media Environment  Allow any device to try to access the medium whenever it has data to send  Use a Carrier Sense Multiple Access (CSMA) process to first detect if the media is carrying a signal  Two CSMA methods: CSMA/Collision Detection (CSMA/CD) - the device monitors the media for the presence of a data signal. If no signal is present, the device transmits (could result in collisions with other data) CSMA/Collision Avoidance (CSMA/CA) - the device examines the media for the presence of a data signal. If the media is free, the device sends a notification across the media of its intent to use it. The device then sends the data.  AKA first come, first serve and non-deterministic

16 Contention-based Access in a Shared Media Environment A closer look at this later…

17  In point-to-point connections, the Data Link layer has to determine whether the communication is half-duplex or full-duplex.  Half Duplex – a station cannot transmit and receive simultaneously Media Access Control For Non-Shared Media

18 Media Access Control For Non-Shared Media Full Duplex – a station can transmit and receive simultaneously

19 The Topology of a Network  The topology of a network is the arrangement/relationship of the network devices and the interconnections between them  Network topologies can be viewed at the physical level and the logical level.  Physical Topology -the arrangement of the nodes and the physical connections between them.  Logical Topology - the way a network transfers frames from one node to the next. The logical signal paths defined by Data Link layer protocols. The logical topology influences the type of network framing and media access control used.  NOTE: The physical or cabled topology of a network will most likely not be the same as the logical topology.

20 A Look at Logical Topologies

21 Logical Point-to-Point Topology  A point-to-point topology connects two nodes directly together  Can operate in either Half-Duplex or Full Duplex

22 Logical Point-to-Point Topology  The logical connection between nodes is sometimes referred to as a virtual circuit

23 Logical Point-to-Point Topologies  Regardless of the number of physical devices within the network cloud, the two nodes act as if they are physically connected to each other.

24  Enables a number of nodes to communicate by using the same shared media (AKA logical bus topology)  Data from only one node can be placed on the medium at a time  Every node sees all the frames that are on the medium, but only the node to which the frame is addressed processes the contents of the frame  Requires a method to regulate the transmission of data and thereby reduce collisions between different signals  Media access control methods used by logical multi-access topologies are: CSMA/CD CSMA/CA Token Passing Logical Multi-Access Topology

25 Logical Multi-Access Topology  A frame sent from source A to destination D will be seen by all devices, including B, C, D, & E.  Only D, the destination, will process the frame.

26 Logical Ring Topology  In a logical ring, all nodes around the ring between the source and destination node examine the frame –If the frame is not addressed to the node, the node passes the frame to the next node  This allows a ring to use a media access control technique called token passing  In token passing, when there is no data being transmitted, a signal (known as a token) may be placed on the media and a node can only place a data frame on the media when it has the token.

27 Logical Ring Topology Node A can transmit once it has the electronic token

28 Addressing and Framing Data  Packets are encapsulated into frames at the Data Link Layer to facilitate the entry and exit of data on media

29 Generic Frame Format Question: What is contained within this field? Answer:

30 Typical Frame Header Fields  Start Frame field - Indicates the beginning of the frame  Source and Destination address fields - Indicates the source and destination nodes on the media  Priority/Quality of Service field - Indicates a particular type of communication service for processing  Type field - Indicates the upper layer service contained in the frame  Logical connection control field - Used to establish a logical connection between nodes  Physical link control field - Used to establish the media link  Flow control field - Used to start and stop traffic over the media  Congestion control field - Indicates congestion in the media

31 The Role of the Frame Trailer- FCS Field  The calculated value placed in the FCS field is called the CRC (cyclic redundancy check)

32 The Role of the Frame Trailer – Stop Frame

33 Layer 2 Protocols Covered in CCNA  Ethernet  Point-to-Point Protocol (PPP)  High-Level Data Link Control (HDLC)  Frame Relay  Asynchronous Transfer Mode (ATM)

34 Selecting a Layer 2 Protocol  When implementing a Layer 2 protocol in a network, the following factors should be considered: –Geographic scope of the network –The physical layer implementation –The number of hosts to be connected  Note: Layer 2 protocols are independent of the upper layer protocols used

35 Ethernet Protocol for LANs  Ethernet is a family of networking technologies that are defined in the IEEE and standards  Ethernet is the most widely used LAN technology and supports data bandwidths of 10, 100, 1000, or 10,000 Mbps.  Ethernet standards define both the Layer 2 protocols and the Layer 1 technologies  The basic frame format remains consistent across all forms of Ethernet  Ethernet provides unacknowledged connectionless service over a shared media using CSMA/CD as the media access methods.  Shared media requires that the Ethernet packet header use a Data Link layer address to identify the source and destination nodes.  As with most LAN protocols, this address is referred to as the MAC address of the node  An Ethernet MAC address is 48 bits and is generally represented in hexadecimal format.

36 The Ethernet II Frame

37 Point-to-Point Protocol (PPP) for WANs  Point-to-Point Protocol (PPP) is a WAN protocol used to deliver frames between two nodes  PPP remains the protocol of choice to implement many serial WANs  PPP can be used on various physical media, including twisted pair, fiber optic lines, and satellite transmission, as well as for virtual connections  PPP also allows the two nodes to negotiate options within the PPP session including: authentication, compression, and multilink (the use of multiple physical connections)

38 PPP Frame WHY?

39 Wireless Protocol for LANs  The Standard IEEE is commonly referred to as Wi-Fi  Uses a 48-bit addressing scheme as other 802 LANs, however there are many differences at the MAC sublayer and Physical layer  A wireless environment requires special considerations since external factors may interfere with data transfer and it is difficult to control access  networks use a contention-based system with the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) media access process.  CSMA/CA specifies a random backoff procedure for all nodes that are waiting to transmit  networks also use Data Link acknowledgements to confirm that a frame is received successfully  If the sending station does not detect the acknowledgement frame, the data frame is retransmitted.

Wireless Frame Fields  Protocol Version field - Version of frame in use  Type and Subtype fields - Identifies one of three functions and sub functions of the frame: control, data, and management  To DS field - Set to 1 in data frames destined for the distribution system (devices in the wireless structure)  From DS field - Set to 1 in data frames exiting the distribution system  More Fragments field - Set to 1 for frames that have another fragment  Retry field - Set to 1 if the frame is a retransmission of an earlier frame  Power Management field - Set to 1 to indicate that a node will be in power-save mode  More Data field - Set to 1 to indicate to a node in power-save mode that more frames are buffered for that node  Wired Equivalent Privacy (WEP) field - Set to 1 if the frame contains WEP encrypted information for security

41  Order field - Set to 1 in a data type frame that uses Strictly Ordered service class (does not need reordering)  Duration/ID field - Depending on the type of frame, represents either the time, in microseconds, required to transmit the frame or an association identity (AID) for the station that transmitted the frame  Destination Address (DA) field - MAC address of the final destination node in the network  Source Address (SA) field - MAC address of the node the initiated the frame  Receiver Address (RA) field - MAC address that identifies the wireless device that is the immediate recipient of the frame  Transmitter Address (TA) field - MAC address that identifies the wireless device that transmitted the frame  Sequence Number field - Indicates the sequence number assigned to the frame; retransmitted frames are identified by duplicate sequence numbers  Fragment Number field - Indicates the number for each fragment of a frame  Frame Body field - Contains the information being transported; for data frames, typically an IP packet  FCS field - Contains a 32-bit cyclic redundancy check (CRC) of the frame Wireless Frame Fields Cont’d…

Wireless Frame