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Hands-on Networking Fundamentals. Chapter 4 Connecting Through a Cabled Network. Communications Media Types. OSI Layer 1: communication media and interfaces Five basic communication media types Coaxial cable: based on copper wire Twisted-pair cable: based on copper wire

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Hands on networking fundamentals

Hands-on Networking Fundamentals

Chapter 4

Connecting Through a Cabled Network

Communications media types
Communications Media Types

  • OSI Layer 1: communication media and interfaces

  • Five basic communication media types

    • Coaxial cable: based on copper wire

    • Twisted-pair cable: based on copper wire

    • Fiber-optic cable: glass or plastic cable

    • Hybrid fiber/coax: combines copper and fiber

    • Wireless technologies: radio or microwaves

  • Suitability of media varies with different networks

    • Example: uses of coaxial cable

      • Older LANs

      • LANs in areas with signal interference strong

      • Connecting wireless antenna to network device

Hands-on Networking Fundamentals

Communications media types continued
Communications Media Types (continued)

  • Consider capabilities and limitations of media

  • Factors affecting choice of LAN or WAN medium

    • Data transfer speed

    • Use in specific network topologies

    • Distance requirements

    • Cable and cable component costs

    • Additional network equipment that might be required

    • Flexibility and ease of installation

    • Immunity to interference from outside sources

    • Upgrade options

    • Security

Hands-on Networking Fundamentals

Coaxial cable
Coaxial Cable

  • Two types of coaxial cable (coax)

    • Thick: used in early networks, typically as backbone

      • Backbone: cabling between network equipment rooms, floors, and buildings

    • Thin: used to connect desktops to LANs

      • Has much smaller diameter than thick coax

  • Use of both thick and thin coaxial cables declining

Hands-on Networking Fundamentals

Twisted pair cable
Twisted Pair Cable

  • Twisted-pair cable

    • Contains pairs of insulated copper wires

    • Outer insulating jacket covers wires

  • Communication specific properties

    • Copper wires twisted to reduce EMI and RFI

    • Length: up to 100 meters

    • Transmission speed: up to 10 Gbps

  • RJ-45 plug-in connector attaches cable to device

    • Less expensive and more flexible than T-connectors

  • Two kinds of twisted pair cable: shielded and unshielded (preferred)

Hands-on Networking Fundamentals

Activity 4 4 building a utp cable
Activity 4-4: Building a UTP Cable

  • Time Required: Approximately 20–30 minutes

  • Objective: Experience building a UTP cable.

  • Description: In this activity, you attach 4-pair UTP cable to an RJ-45 connector. You need the cable, a crimper, a connector, and a wire stripper. These instructions and Figure 4-6 follow the EIA/TIA-568-B standard.

Hands-on Networking Fundamentals

Fiber optic cable
Fiber-Optic Cable

  • Fiber-optic cable

    • One or more glass or plastic fiber cores encased in glass tube (cladding)

    • Fiber cores and cladding are surrounded by PVC cover

    • Signal transmissions consist light (usually infrared)

  • Three commonly used fiber-optic cable sizes

    • 50/125 micron

      • Micron (μm): millionth of a meter

      • 50 represents core diameter

      • 125 represents cladding diameter

    • 62.5/125 micron

    • 100/140 micron

Hands-on Networking Fundamentals

Gigabit ethernet
Gigabit Ethernet

  • Gigabit Ethernet (1000BaseX)

    • Provides data transfer of up to 1 Gbps

    • Uses CSMA/CD access methods

    • Upgrade path for 100BaseX Ethernet networks

  • Uses of Gigabit Ethernet

    • Alternative for backbone LAN congestion

    • Attract token ring users with star-based topologies

  • Gigabit Ethernet target

    • Installations using Layer 3 routed communications

  • Separate standards for fiber-optic and twisted-pair cables

Hands-on Networking Fundamentals

The role of firmware and nic drivers
The Role of Firmware and NIC Drivers

  • Firmware and NIC driver support communications

    • Firmware: software stored on a chip, such as ROM

    • NIC Driver: manages how packets or frames sent

  • Firmware or driver may automatically detect media

  • Some NIC drivers can be signed

  • Driver signing: placing digital signature in driver

  • Functions of digital signature

    • Ensures driver compatible with operating system

    • Certifies that driver tested for defects or viruses

    • Ensures that driver cannot overwrite new driver

Hands-on Networking Fundamentals

Half and full duplex nic communications
Half- and Full-Duplex NIC Communications

  • Two transmission modes for NIC and network equipment

    • Half-duplex: send and receive, not at the same time

    • Full-duplex: parallel sending and receiving

      • Made possible by buffering at NIC

      • Buffering: temporarily storing information

  • Full-duplex is a good choice

    • Usually faster than half-duplex

Hands-on Networking Fundamentals

Hands on networking fundamentals1

Hands-on Networking Fundamentals

Chapter 5

Devices for Connecting Networks

Lan transmission devices
LAN Transmission Devices

  • Uses of LAN transmission equipment

    • Connecting devices on a single network

    • Creating and linking multiple networks or subnetworks

    • Setting up some enterprise networks

  • Connecting devices that will be discussed

    • Repeaters, MAUs, hubs, bridges, routers, brouters, switches, gateways

Hands-on Networking Fundamentals


  • Connects two or more cable segments

  • Retransmits incoming signal to all other segments

  • Cable segment is run within IEEE specifications

    • Example: Ethernet segment in star-bus network

  • Performs four Physical layer functions

    • Filter out signal disturbance caused by EMI and RFI

    • Amplify and reshape incoming signal

    • Retime the signal (in Ethernet applications)

    • Reproduce the signal on all cable runs

Hands-on Networking Fundamentals

Multistation access unit
Multistation Access Unit

  • Multistation access unit (MAU or MSAU)

    • Central hub on a token ring network

    • May have intelligence built-in to detect problems

      • Smart multistation access unit (SMAU)

  • Tasks performed by MAU

    • Connect nodes in a logical ring upon a physical star

    • Move the token and frames around the ring

    • Amplify data signals

    • Expand token ring network by daisy-chain connections

    • Provide for orderly movement of data

    • Shut down ports to malfunctioning nodes

Hands-on Networking Fundamentals


  • Central network device connecting nodes in star

  • Functions of a hub

    • Centrally connect multiple nodes into one network

    • Permit connections on single or multiple LANs

    • Provide multi-protocol services

    • Consolidate the network backbone

    • Provide connections for several different media types

    • Enable centralized network management and design

  • Unmanaged hub (simplest)

    • Logical bus or token ring physically connected as star

    • May be active or passive

Hands-on Networking Fundamentals


  • Network device connecting LAN segments

  • Functions of a bridge

    • Extend LAN when maximum connection limit reached

      • Example: the 30-node limit on an Ethernet bus

    • Extend a LAN beyond the length limit

      • Example: beyond 185 meters for thinnet segment

    • Segment LANs to reduce data traffic bottlenecks

    • Prevent unauthorized access to a LAN

  • Operates in promiscuous mode

    • Examine frame's physical destination address

    • Occurs at MAC sublayer of OSI Data Link layer

Hands-on Networking Fundamentals

Bridge continued
Bridge (continued)

  • Translational bridge

    • Converts frame to new access method and media type

    • Example: from token ring to Ethernet

      • Discards addressing information not used in Ethernet

  • Three primary bridge functions

    • Learning: learn network topology and device addresses

      • Information stored in a bridging table

    • Filtering: do not flood certain frames, discard others

      • Enables bridge to used for security purposes

    • Forwarding: transmit frames to destination

      • Based on data built-in to bridging table

  • Some bridges are used to cascade network segments

Hands-on Networking Fundamentals

Spanning tree algorithm
Spanning Tree Algorithm

  • Defined by the IEEE 802.1d standard

    • Bridges frames in networks with more than two bridges

    • Sets up a system of checks performed by bridges

  • Two motivations for using spanning tree algorithm

    • Ensure a frame does not enter infinite loop

      • Causes congestion that may intensify to broadcast storm

    • Forward frames along the most efficient route

      • Efficiency based on distance and utilization of resources

  • Services for frames performed by algorithm

    • Create one-way path around network (use bridge data)

    • Establish maximum number of hops for maximum route

    • Enable bridges to send frames along best route

Hands-on Networking Fundamentals


  • Learns, filters, and forwards like a bridge

  • Differs from a bridge in significant ways

    • Connect LANs at the Network layer of the OSI model

    • Add intelligence to bridge capabilities

    • Receive regular communications from nodes

  • General functions of a router

    • Reduce traffic by efficiently directing packets

    • Join neighboring or distant networks

    • Connect dissimilar networks

    • Prevent bottlenecks by isolating portions of a network

    • Secure portions of a network by acting as a firewall

Hands-on Networking Fundamentals

Router continued
Router (continued)

  • Uses a metric to determine optimal routes

  • Components which may inform metric calculation

    • Number of incoming packets waiting at a particular router port

    • Number of hops between sending and receiving segments

    • Number of packets that can be handled in time frame

    • Size of the packet (large packet may be subdivided)

    • Bandwidth (speed) between two communicating nodes

    • Whether a particular network segment is available

  • May isolate segments to avert congestion

Hands-on Networking Fundamentals

Static and dynamic routing
Static and Dynamic Routing

  • Static routing requires routing tables

    • Routing tables specify paths between routers

    • Tables set up and maintained by network administrator

  • Dynamic routing independent of network administrator

  • Functions automatically performed in dynamic routing

    • Determine which other routers can be reached

    • Determine shortest paths to other networks with metrics

    • Determine when path to a router is down or unusable

    • Use metrics to reconfigure alternative routes

    • Rediscover router and network path after restoration

Hands-on Networking Fundamentals

Routing tables and protocols
Routing Tables and Protocols

  • Routers maintain two important databases

    • Routing table: contains addresses of other routers

    • Network status: contains information about traffic, topology, and status of links

  • Databases updated by regular exchange of data

  • Router forwards packet on basis of metrics

  • Routers use one or more protocols

    • Multiprotocol type: each protocol has address database

  • Two common communication protocols: RIP and OSPF

Hands-on Networking Fundamentals

Routing tables and protocols continued
Routing Tables and Protocols (continued)

  • Routing Information Protocol (RIP)

    • Determines shortest number of hops to other routers

    • Information added to each router's table

    • Disadvantages

      • Updates containing entire routing table create traffic

      • Only uses hop count as a metric

  • Open Shortest Path First (OSPF) protocol

    • Sends only portion of table related to immediate links

    • Packages routing information in compact form

  • Local routers: LAN-based

    • Join LANs; segment traffic; act as firewalls

Hands-on Networking Fundamentals


  • Dual purpose

    • To provide bridging capacity

    • To increase bandwidth

  • Bridge-like characteristics of switch

    • Operates at Data Link MAC sublayer

    • Uses table information to filter and forward traffic

  • LAN uses two switching techniques (fabric)

    • Cut-through: forward portions of frame

    • Store-and-forward: frame buffered until link available

Hands-on Networking Fundamentals


  • Software or hardware interface

    • Enables two networked or software systems to link

  • Functions of a gateway

    • Convert common protocols to specialized type

    • Convert message formats from one format to another

    • Translate different addressing schemes

    • Link a host computer to a LAN

    • Provide terminal emulation for connections to host

    • Direct electronic mail to the right network destination

    • Connect networks with different architectures

  • Can function at any OSI layer

Hands-on Networking Fundamentals

Wan transmission devices
WAN Transmission Devices

  • WAN transmission over two network types

    • PSTN (public switched telephone networks)

    • Leased telephone lines such as T-carrier or ISDN

  • Characteristics of WAN transmission equipment

    • May have analog component or be completely digital

    • Converts signal for long distance communications

    • Creates multiple channels in medium (grow bandwidth)

  • Frequently used WAN transmission devices

    • Telephone modems, ISDN adapters, cable TV modems, DSL modems/routers, access servers, routers

Hands-on Networking Fundamentals

Telephone modems
Telephone Modems

  • Modem (modulator/demodulator)

    • Converts outgoing binary (computer) signal to analog

    • Converts incoming analog signal to a binary signal

  • Two ways to attach a modem to a computer

    • Internal: installed in computer using expansion slot

    • External: attached to serial port connector via cable

  • Three common types of connectors

    • DB-25 connector, DB-9 connector, USB

  • Modem data transfer rate measured in two ways

    • Baud rate: number of signal events per second

    • Bits per second (bps): bits per second

Hands-on Networking Fundamentals

Telephone modems continued
Telephone Modems (continued)

  • Data terminal equipment (DTE)

    • Device that prepares data for transmission

    • Data transfer speed of PC is DTE communications rate

  • Data communications equipment (DCE)

    • Device (modem) that converts data from DTE

    • Speed of modem is DCE communications rate

  • Modems use two communication formats

    • Synchronous: continuous data bursts controlled by clock

    • Asynchronous: discrete signals delimited by start and stop bits

Hands-on Networking Fundamentals

Cable tv modems
Cable TV Modems

  • Uses two channels to communicate

    • Upstream: transmit outgoing data, sound, TV signals

    • Downstream: receive and blend incoming signals

  • Factors affecting transmission speed

    • Modem speeds may differ upstream and downstream

      • Example: 30 Mbps upstream, 15 Mbps downstream

    • Maximum bandwidth reduced by other subscribers

      • Cable hub handles maximum of 30 Mbps

      • Cable service may impose policy limits

  • Data Over Cable Service Interface Spec (DOCSIS)

    • Also called Certified Cable Modem Project

    • Provides standards and certifications

Hands-on Networking Fundamentals

Dsl modems and routers
DSL Modems and Routers

  • Digital Subscriber Line (DSL)

    • Works over copper wire likes ISDN

    • Requires intelligent adapter in connecting computer

      • Intelligent adapter: sends digital signal over copper wire

  • Simplex communication over copper wire

    • Dedicated lines for incoming and outgoing signals

  • Transfer 2.3 Mbps upstream, 52 Mbps downstream

  • Advantages of DSL over cable

    • Dedicated DSL line more secure

    • Dedicated DSL provides full bandwidth

  • DSL networks utilize combined DSL adapter/router

Hands-on Networking Fundamentals

Remote routers
Remote Routers

  • Operate over long distances

    • Connect ATM, ISDN, frame relay, high-speed serial, and X.25 networks

    • Example: connect networks from NY to LA into WAN

  • Similarities with local routers

    • Can support multiple protocols

    • Can be set up as a firewall

  • Most routers connect to WAN through serial interface

    • CSU/DSU for T-carrier communications

      • Channel service unit (CSU): interface to T-carrier line

      • Data service unit (DSU): digital interface to CSU

    • Modular adapter for other high-speed connections

Hands-on Networking Fundamentals