ITE PC v4.0 Chapter 1

Chapter 4:Network AccessIntroduction to Networks 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID#Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential1Cisco Networking Academy programIntroduction to NetworksChapter 4: Network Access 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrChapter 4: ObjectivesUpon completion of this chapter, you will be able to:Identify device connectivity options.Describe the purpose and functions of the physical layer in the network.Describe basic principles of the physical layer standards.Identify the basic characteristics of copper cabling.Build a UTP cable used in Ethernet networks.Describe fiber-optic cabling and its main advantages over other media.Describe wireless media.Select the appropriate media for a given requirement and connect devices.Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential2Chapter 4 Objectives 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrChapter 4: Objectives (cont.)Upon completion of this chapter, you will be able to:Describe the purpose and function of the data link layer in preparing communication for transmission on specific media.Describe the Layer 2 frame structure and identify generic fields.Identify several sources for the protocols and standards used by the data link layer.Compare the functions of logical topologies and physical topologies.Describe the basic characteristics of media control methods on WAN topologies.Describe the basic characteristics of media control methods on LAN topologies.Describe the characteristics and functions of the data link frame.

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential3Chapter 4 Objectives (cont.) 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr4.4 Media Access Control 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID#Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential4Cisco Networking Academy programIntroduction to NetworksChapter 4: Network Access 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrChapter 44.1 Physical Layer Protocols4.2 Network Media4.3 Data Link Layer Protocols4.4 Media Access Control4.5 SummaryPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential5Chapter 4 Sections 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr4.1 Physical Layer Protocols 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID#Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential6Cisco Networking Academy programIntroduction to NetworksChapter 4: Network Access 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrGetting it ConnectedConnecting to the Network (cont.)

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential84.1.1.1 Connecting to the Network (cont.) 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrGetting it ConnectedNetwork Interface CardsConnecting to the Wireless LAN with a Range Extender

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential94.1.1.2 Network Interface Cards 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrPurpose of the Physical LayerThe Physical Layer

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential104.1.2.1 The Physical Layer 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrPurpose of the Physical LayerPhysical Layer Media

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential114.1.2.2 Physical Layer Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrPurpose of the Physical LayerPhysical Layer StandardsStandard OrganizationNetworking Standards ISOISO 8877: Officially adopted the RJ connectors (e.g., RJ-11, RJ-45)ISO 11801: Network cabling standard similar to EIA/TIA 568.EIA/TIATIA-568-C: Telecommunications cabling standards, used by nearly all voice, video and data networks.TIA-569-B: Commercial Building Standards for Telecommunications Pathways and SpacesTIA-598-C: Fiber optic color codingTIA-942: Telecommunications Infrastructure Standard for Data CentersANSI568-C: RJ-45 pinouts. Co-developed with EIA/TIAITU-TG.992: ADSLIEEE802.3: Ethernet802.11: Wireless LAN (WLAN) & Mesh (Wi-Fi certification)802.15: BluetoothPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential124.1.2.3 Physical Layer Standards 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrFundamental Principles of Layer 1Physical Layer Fundamental PrinciplesMediaPhysical ComponentsFrame Encoding TechniqueSignalling MethodCopper CableUTPCoaxialConnectorsNICsPortsInterfacesManchester EncodingNon-Return to Zero (NRZ) techniques4B/5B codes are used with Multi-Level Transition Level 3 (MLT-3) signaling8B/10BPAM5Changes in the electromagnetic fieldIntensity of the electromagnetic field Phase of the electromagnetic waveFiber Optic CableSingle-mode FiberMultimode FiberConnectorsNICsInterfacesLasers and LEDsPhotoreceptorsPulses of lightWavelength multiplexing using different colorsA pulse equals 1.No pulse is 0. Wireless MediaAccess PointsNICsRadioAntennae DSSS (direct-sequence spread-spectrum)OFDM (orthogonal frequency division multiplexing)Radio wavesPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential134.1.3.1 Physical Layer Fundamental Principles 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrFundamental Principles of Layer 1Bandwidth

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential144.1.3.2 Bandwidth 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrFundamental Principles of Layer 1Throughput

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential154.1.3.3 Throughput 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Fundamental Principles of Layer 1Types of Physical Media

Gigabit Ethernet InterfacesSHDSLInterfaceManagementPortsFastEthernet Switch PortsUSB Mini-BConnectorUSB Type A ConnectorPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential164.1.3.4 Types of Physical Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr4.2 Network Media 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID#Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential17Cisco Networking Academy programIntroduction to NetworksChapter 4: Network Access 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Copper CablingCharacteristics of Copper Media

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential184.2.1.1 Characteristics of Copper Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Copper CablingCopper Media

Shielded Twisted Pair (STP) CableUnshielded Twisted Pair (UTP) CableCoaxial CablePresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential194.2.1.2 Copper Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Copper CablingUTP Cable

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential204.2.1.3 Unshielded Twisted-Pair Cable 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Copper CablingSTP Cable

Foil ShieldsBraided or Foil ShieldPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential214.2.1.4 Shielded Twisted-Pair (STP) Cable 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Copper CablingCoaxial Cable

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential224.2.1.5 Coaxial Cable 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Copper CablingCooper Media Safety

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential234.2.1.6 Copper Media Safety 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

UTP CablingProperties of UTP CablingUTP cable does not use shielding to counter the effects of EMI and RFI. Instead, cable designers have discovered that they can limit the negative effect of crosstalk by:CancellationVarying the number of twists per wire pair

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential244.2.2.1 Properties of UTP Cabling 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

UTP CablingUTP Cabling Standards

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential254.2.2.2 UTP Cabling Standards 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

UTP CablingUTP Connectors

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential264.2.2.3 UTP Connectors 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

UTP CablingTypes of UTP Cable

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential274.2.2.4 Types of UTP Cable 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

UTP CablingTesting UTP CablesAfter installation, a UTP cable tester should be used to test for the following parameters:Wire mapCable lengthSignal loss due to attenuationCrosstalk

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential284.2.2.5 Testing UTP Cables 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Fiber Optic CablingProperties of Fiber Optic CablingFiber-optic cabling is now being used in four types of industry:Enterprise NetworksFiber-to-the-home (FTTH) and Access NetworksLong-Haul NetworksSubmarine Networks

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential294.2.3.1 Properties of Fiber Optic Cabling 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Fiber Optic CablingFiber Media Cable Design

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential304.2.3.2 Fiber Media Cable Design 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Fiber Optic CablingTypes of Fiber Media

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential314.2.3.3 Types of Fiber Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Fiber Optic CablingNetwork Fiber Connectors

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential324.2.3.4 Network Fiber Connectors 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Fiber Optic CablingTesting Fiber Cables

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential334.2.3.5 Testing Fiber Cables 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Fiber Optic CablingFiber versus CopperImplementation IssuesCopper MediaFibre OpticBandwidth Supported10 Mbps 10 Gbps10 Mbps 100 GbpsDistanceRelatively short(1 100 meters)Relatively High(1 100,000 meters)Immunity To EMI And RFILowHigh(Completely immune)Immunity To Electrical HazardsLowHigh(Completely immune)Media And Connector CostsLowestHighestInstallation Skills RequiredLowestHighestSafety PrecautionsLowestHighestPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential344.2.3.6 Fiber versus Copper 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Wireless MediaProperties of Wireless MediaWireless does have some areas of concern including:Coverage areaInterferenceSecurity

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential354.2.4.1 Properties of Wireless Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrIEEE 802.11 standardsCommonly referred to as Wi-Fi.Uses CSMA/CAVariations include:802.11a: 54 Mbps, 5 GHz802.11b: 11 Mbps, 2.4 GHz802.11g: 54 Mbps, 2.4 GHz802.11n: 600 Mbps, 2.4 and 5 GHz802.11ac: 1 Gbps, 5 GHz802.11ad: 7 Gbps, 2.4 GHz, 5 GHz, and 60 GHzIEEE 802.15 standardSupports speeds up to 3 Mb/sProvides device pairing over distances from 1 to 100 meters.IEEE 802.16 standardProvides speeds up to 1 GbpsUses a point-to-multipoint topology to provide wireless broadband access.

Wireless MediaTypes of Wireless Media

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential364.2.4.2 Types of Wireless Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Wireless MediaWireless LANCisco Linksys EA6500 802.11ac Wireless Router

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential374.2.4.3 Wireless LAN 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Wireless Media802.11 Wi-Fi StandardsStandardMaximum SpeedFrequencyBackwards Compatible802.11a54 Mbps5 GHzNo802.11b11 Mbps2.4 GHzNo802.11g54 Mbps2.4 GHz802.11b802.11n600 Mbps2.4 GHz or 5 GHz802.11b/g802.11ac 1.3 Gbps(1300 Mbps)2.4 GHz and 5.5 GHz 802.11b/g/n802.11ad7 Gbps(7000 Mbps)2.4 GHz, 5 GHz and 60 GHz 802.11b/g/n/acPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential384.2.4.4 802.11 Wi-Fi Standards 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr4.3 Data Link Layer Protocols 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID#Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential39Cisco Networking Academy programIntroduction to NetworksChapter 4: Network Access 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrPurpose of the Data Link LayerThe Data Link Layer

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential404.3.1.1 The Data Link Layer 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrPurpose of the Data Link LayerData Link SublayersNetworkData LinkLLC SublayerMAC SublayerPhysical802.3 Ethernet802.11 Wi-Fi802.15 BluetoothPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential414.3.1.2 Data Link Sublayers 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrPurpose of the Data Link LayerMedia Access Control

The Data Link LayerPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential424.3.1.3 Media Access Control 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrPurpose of the Data Link LayerProviding Access to Media

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential434.3.1.4 Providing Access to Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link LayerFormatting Data for Transmission

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential444.3.2.1 Formatting Data for Transmission 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrLayer 2 Frame StructureCreating a Frame

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential454.3.2.2 Creating a Frame 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrLayer 2 StandardsData Link Layer StandardsStandard organizationNetworking Standards IEEE802.2: Logical Link Control (LLC)802.3: Ethernet802.4: Token bus802.5: Token passing802.11: Wireless LAN (WLAN) & Mesh (Wi-Fi certification)802.15: Bluetooth802.16: WiMaxITU-TG.992: ADSLG.8100 - G.8199: MPLS over Transport aspectsQ.921: ISDN Q.922: Frame RelayISOHDLC (High Level Data Link Control)ISO 9314: FDDI Media Access Control (MAC)ANSIX3T9.5 and X3T12: Fiber Distributed Data Interface (FDDI) Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential464.3.3.1 Data Link Layer Standards 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrTopologiesControlling Access to the Media

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential474.4.1.1 Controlling Access to the Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

TopologiesPhysical and Logical TopologiesPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential484.4.1.2 Physical and Logical Topologies 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

TopologiesPhysical and Logical Topologies (cont.)Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential494.4.1.2 Physical and Logical Topologies (cont.) 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrWAN TopologiesCommon Physical WAN Topologies

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential504.4.2.1 Common Physical WAN Topologies 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrWAN TopologiesPhysical Point-to-Point Topology

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential514.4.2.2 Physical Point-to-Point Topology 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrWAN TopologiesLogical Point-to-Point Topology

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential524.4.2.3 Logical Point-to-Point Topology 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrWAN TopologiesHalf- and Full-Duplex

Half-DuplexFull-DuplexPresentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential534.4.2.4 Half and Full Duplex 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrLAN TopologiesPhysical LAN Topologies

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential544.4.3.1 Physical LAN Topologies 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrLAN TopologiesLogical Topology for Shared Media

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential554.4.3.2 Logical Topology for Shared Media 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrLAN TopologiesContention-Based AccessCharacteristicsContention-Based TechnologiesStations can transmit at any timeCollision existThere are mechanisms to resolve contention for the mediaCSMA/CD for 802.3 Ethernet networksCSMA/CA for 802.11 wireless networks

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential564.4.3.3 Contention-Based Access 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrLAN TopologiesMulti-Access Topology

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential574.4.3.4 Multi-Access Topology 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrLAN TopologiesControlled AccessCharacteristicsControlled Access TechnologiesOnly one station can transmit at a timeDevices wanting to transmit must wait their turnNo collisionsMay use a token passing methodToken Ring (IEEE 802.5)FDDI

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential584.4.3.5 Controlled Access 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrLAN TopologiesRing Topology

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential594.4.3.6 Ring Topology 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link FrameThe Frame

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential604.4.4.1 The Frame 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link FrameThe Header

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential614.4.4.2 The Header 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link FrameLayer 2 Address

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential624.4.4.3 Layer 2 Address 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link FrameThe Trailer

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential634.4.4.4 The Trailer 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link FrameLAN and WAN Frames

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential644.4.4.5 LAN and WAN Frames 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link FrameEthernet Frame

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential654.4.4.6 Ethernet Frame 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link FramePoint-to-Point Protocol Frame

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential664.4.4.7 PPP Frame 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrData Link Frame802.11 Wireless Frame

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential674.4.4.8 802.11 Wireless Frame 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrNetwork AccessSummaryThe TCP/IP network access layer is the equivalent of the OSI data link layer (Layer 2) and the physical layer (Layer 1).The OSI physical layer provides the means to transport the bits that make up a data link layer frame across the network media. The physical layer standards address three functional areas: physical components, frame encoding technique, and signaling method.Using the proper media is an important part of network communications. Without the proper physical connection, either wired or wireless, communications between any two devices will not occur.Wired communication consists of copper media and fiber cable.There are three main types of copper media used in networking: unshielded-twisted pair (UTP), shielded-twisted pair (STP), and coaxial cable. UTP cabling is the most common copper networking media.Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential68Chapter 4 Summary 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrNetwork AccessSummary (cont.)Optical fiber cable has become very popular for interconnecting infrastructure network devices. It permits the transmission of data over longer distances and at higher bandwidths (data rates) than any other networking media. Wireless media carry electromagnetic signals that represent the binary digits of data communications using radio or microwave frequencies.The data link layer is responsible for the exchange of frames between nodes over a physical network media. It allows the upper layers to access the media and controls how data is placed and received on the media.Among the different implementations of the data link layer protocols, there are different methods of controlling access to the media. These media access control techniques define if and how the nodes share the media. The actual media access control method used depends on the topology and media sharing. LAN and WAN topologies can be physical or logical.Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential69Chapter 4 Summary (cont.) 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scrNetwork AccessSummary (cont.)WANs are commonly interconnected using the point-to-point, hub and spoke, or mesh physical topologies. In shared media LANs, end devices can be interconnected using the star, bus, ring, or extended star (hybrid) physical topologies.All data link layer protocols encapsulate the Layer 3 PDU within the data field of the frame. However, the structure of the frame and the fields contained in the header and trailer vary according to the protocol.Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential70Chapter 4 Summary (cont.) 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr

Presentation_ID# 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential