chapter4_network access.pdf
TRANSCRIPT
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2008 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 1
Chapter 4:
Network Access
Introduction to Networks
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Presentation_ID 2 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Chapter 4: Objectives
Upon completion of this chapter, you will be able to:
Identify device connectivity options.
Describe the purpose and functions of the physical layer in thenetwork.
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 othermedia.
Describe wireless media.
Select the appropriate media for a given requirement and connectdevices.
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Presentation_ID 3 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Chapter 4: Objectives (cont.)
Upon completion of this chapter, you will be able to:
Describe the purpose and function of the data link layer inpreparing 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 bythe data link layer.
Compare the functions of logical topologies and physicaltopologies.
Describe the basic characteristics of media control methods onWAN topologies.
Describe the basic characteristics of media control methods onLAN topologies.
Describe the characteristics and functions of the data link frame.
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2008 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 4
4.4 Media Access Control
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Presentation_ID 5 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Chapter 4
4.1 Physical Layer Protocols4.2 Network Media
4.3 Data Link Layer Protocols
4.4 Media Access Control
4.5 Summary
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4.1 Physical Layer Protocols
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Getting it Connected
Connecting to the Network
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Getting it Connected
Connecting to the Network (cont.)
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Getting it Connected
Network Interface Cards
Connecting to the Wireless LAN with a Range Extender
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Purpose of the Physical Layer
The Physical Layer
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Purpose of the Physical Layer
Physical Layer Media
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Purpose of the Physical Layer
Physical Layer Standards
Standard
OrganizationNetworking Standards
ISO ISO 8877: Officially adopted the RJ connectors (e.g., RJ-11, RJ-45)
ISO 11801: Network cabling standard similar to EIA/TIA 568.
EIA/TIA
TIA-568-C: Telecommunications cabling standards, used by nearly allvoice, video and data networks.
TIA-569-B: Commercial Building Standards for Telecommunications
Pathways and Spaces
TIA-598-C: Fiber optic color coding
TIA-942: Telecommunications Infrastructure Standard for Data Centers
ANSI 568-C: RJ-45 pinouts. Co-developed with EIA/TIA
ITU-T G.992: ADSL
IEEE 802.3: Ethernet
802.11: Wireless LAN (WLAN) & Mesh (Wi-Fi certification)
802.15: Bluetooth
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Fundamental Principles of Layer 1
Physical Layer Fundamental Principles
MediaPhysical
Components
Frame Encoding
TechniqueSignalling Method
Copper
Cable
UTP
Coaxial
Connectors
NICs
Ports
Interfaces
Manchester Encoding
Non-Return to Zero (NRZ)
techniques
4B/5B codes are used with
Multi-Level Transition Level 3(MLT-3) signaling
8B/10B
PAM5
Changes in the
electromagnetic field
Intensity of the
electromagnetic field
Phase of theelectromagnetic
wave
Fiber Optic
Cable
Single-mode Fiber
Multimode Fiber
Connectors
NICs Interfaces
Lasers and LEDs
Photoreceptors
Pulses of light
Wavelength multiplexing using
different colors
A pulse equals 1.
No pulse is 0.
Wireless
Media
Access Points
NICs
Radio
Antennae
DSSS (direct-sequence
spread-spectrum)
OFDM (orthogonal frequency
division multiplexing)
Radio waves
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Fundamental Principles of Layer 1
Bandwidth
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Fundamental Principles of Layer 1
Throughput
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Fundamental Principles of Layer 1
Types of Physical Media
Gigabit EthernetInterfaces
SHDSLInterface
ManagementPorts
FastEthernetSwitch Ports
USB Mini-BConnector
USB Type AConnector
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4.2 Network Media
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Copper Cabling
Characteristics of Copper Media
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Copper Cabling
Copper Media
Shielded TwistedPair (STP) Cable
Unshielded TwistedPair (UTP) Cable
Coaxial Cable
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Copper Cabling
UTP Cable
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Copper Cabling
STP Cable
Foil Shields
Braided or Foil Shield
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Copper Cabling
Coaxial Cable
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Copper Cabling
Cooper Media Safety
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UTP Cabling
Properties of UTP Cabling
UTP cable does not use shielding to counter the effects of EMI andRFI. Instead, cable designers have discovered that they can limit thenegative effect of crosstalk by:
Cancellation
Varying the number of twists per wire pair
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Presentation_ID 25 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
UTP Cabling
UTP Cabling Standards
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UTP Cabling
UTP Connectors
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UTP Cabling
Types of UTP Cable
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UTP Cabling
Testing UTP Cables
After installation, a UTP cable tester should be used to test for the followingparameters:
Wire map
Cable length
Signal loss due to attenuation Crosstalk
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Fiber Optic Cabling
Properties of Fiber Optic Cabling
Fiber-optic cabling is now being used in four types of industry: Enterprise Networks
Fiber-to-the-home (FTTH) and Access Networks
Long-Haul Networks
Submarine Networks
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Presentation_ID 30 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Fiber Optic Cabling
Fiber Media Cable Design
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Fiber Optic Cabling
Types of Fiber Media
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Fiber Optic Cabling
Network Fiber Connectors
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Fiber Optic Cabling
Testing Fiber Cables
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Fiber Optic Cabling
Fiber versus Copper
Implementation Issues Copper Media Fibre Optic
Bandwidth Supported 10 Mbps 10 Gbps 10 Mbps 100 Gbps
DistanceRelatively short
(1 100 meters)
Relatively High
(1 100,000 meters)
Immunity To EMI And RFI LowHigh
(Completely immune)
Immunity To Electrical Hazards LowHigh
(Completely immune)
Media And Connector Costs Lowest Highest
Installation Skills Required Lowest Highest
Safety Precautions Lowest Highest
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Wireless Media
Properties of Wireless Media
Wireless does have some areas of concern including: Coverage area
Interference
Security
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IEEE 802.11 standards
Commonly referred to as Wi-Fi.
Uses CSMA/CA
Variations include:
802.11a: 54 Mbps, 5 GHz
802.11b: 11 Mbps, 2.4 GHz
802.11g: 54 Mbps, 2.4 GHz
802.11n: 600 Mbps, 2.4 and 5 GHz 802.11ac: 1 Gbps, 5 GHz
802.11ad: 7 Gbps, 2.4 GHz, 5 GHz, and 60 GHz
IEEE 802.15 standard
Supports speeds up to 3 Mb/s
Provides device pairing over distances from 1 to 100
meters.
IEEE 802.16 standard
Provides speeds up to 1 Gbps
Uses a point-to-multipoint topology to provide
wireless broadband access.
Wireless Media
Types of Wireless Media
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Presentation_ID 37 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Wireless Media
Wireless LAN
Cisco Linksys EA6500 802.11ac Wireless Router
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Wireless Media
802.11 Wi-Fi Standards
StandardMaximum
SpeedFrequency
Backwards
Compatible
802.11a54 Mbps 5 GHz No
802.11b 11 Mbps 2.4 GHz No
802.11g 54 Mbps 2.4 GHz 802.11b
802.11n 600 Mbps 2.4 GHz or 5 GHz 802.11b/g
802.11ac1.3 Gbps
(1300 Mbps)
2.4 GHz and 5.5
GHz802.11b/g/n
802.11ad7 Gbps
(7000 Mbps)
2.4 GHz, 5 GHz and
60 GHz802.11b/g/n/ac
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4.3 Data Link Layer Protocols
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Purpose of the Data Link Layer
The Data Link Layer
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Purpose of the Data Link Layer
Data Link Sublayers
Network
Data Link
LLC Sublayer
MAC Sublayer
Physical
802
.3
Ethernet
802.1
1
Wi-Fi
802.1
5
Bluetooth
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Purpose of the Data Link Layer
Media Access Control
The Data Link Layer
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Purpose of the Data Link Layer
Providing Access to Media
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Data Link Layer
Formatting Data for Transmission
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Layer 2 Frame Structure
Creating a Frame
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Layer 2 Standards
Data Link Layer Standards
Standardorganization
Networking Standards
IEEE
802.2: Logical Link Control (LLC)
802.3: Ethernet
802.4: Token bus
802.5: Token passing
802.11: Wireless LAN (WLAN) & Mesh (Wi-Fi certification)
802.15: Bluetooth
802.16: WiMax
ITU-T
G.992: ADSL
G.8100 - G.8199: MPLS over Transport aspects
Q.921: ISDN
Q.922: Frame Relay
ISO HDLC (High Level Data Link Control)
ISO 9314: FDDI Media Access Control (MAC)
ANSI X3T9.5 and X3T12: Fiber Distributed Data Interface (FDDI)
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Topologies
Controlling Access to the Media
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Topologies
Physical and Logical Topologies
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Topologies
Physical and Logical Topologies (cont.)
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WAN Topologies
Common Physical WAN Topologies
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WAN Topologies
Physical Point-to-Point Topology
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WAN Topologies
Logical Point-to-Point Topology
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WAN Topologies
Half- and Full-Duplex
Half-Duplex
Full-Duplex
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LAN Topologies
Physical LAN Topologies
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LAN Topologies
Logical Topology for Shared Media
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LAN Topologies
Contention-Based Access
Characteristics Contention-Based Technologies
Stations can transmit at any time Collision exist
There are mechanisms to resolve
contention for the media
CSMA/CD for 802.3 Ethernet networks CSMA/CA for 802.11 wireless networks
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LAN Topologies
Multi-Access Topology
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LAN Topologies
Controlled Access
Characteristics Controlled Access Technologies
Only one station can transmit at a time Devices wanting to transmit must wait
their turn
No collisions
May use a token passing method
Token Ring (IEEE 802.5) FDDI
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LAN Topologies
Ring Topology
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Data Link Frame
The Frame
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Data Link Frame
The Header
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Data Link Frame
Layer 2 Address
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Data Link Frame
The Trailer
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Data Link Frame
LAN and WAN Frames
D Li k F
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Data Link Frame
Ethernet Frame
D t Li k F
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Data Link Frame
Point-to-Point Protocol Frame
D t Li k F
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Data Link Frame
802.11 Wireless Frame
N t k A
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Network Access
Summary
The TCP/IP network access layer is the equivalent of the OSI data linklayer (Layer 2) and the physical layer (Layer 1).
The OSI physical layer provides the means to transport the bits that makeup 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 coaxialcable. UTP cabling is the most common copper networking media.
N t k A
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Network Access
Summary (cont.)
Optical fiber cable has become very popular for interconnectinginfrastructure network devices. It permits the transmission of data overlonger distances and at higher bandwidths (data rates) than any othernetworking media.
Wireless media carry electromagnetic signals that represent the binarydigits of data communications using radio or microwave frequencies.
The data link layer is responsible for the exchange of frames betweennodes over a physical network media. It allows the upper layers to accessthe 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 mediaaccess control techniques define if and how the nodes share the media.
The actual media access control method used depends on the topologyand media sharing. LAN and WAN topologies can be physical or logical.
Network Access
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Network Access
Summary (cont.)
WANs are commonly interconnected using the point-to-point, hub andspoke, 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 fieldscontained in the header and trailer vary according to the protocol.
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