Download Hands-on Networking Fundamentals

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
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
2
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
3
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
4
Hands-on Networking Fundamentals
5
Hands-on Networking Fundamentals
6
Hands-on Networking Fundamentals
7
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
8
Hands-on Networking Fundamentals
9
Hands-on Networking Fundamentals
10
Hands-on Networking Fundamentals
11
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-568B standard.
Hands-on Networking Fundamentals
12
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
13
Hands-on Networking Fundamentals
14
Hands-on Networking Fundamentals
15
Hands-on Networking Fundamentals
16
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
17
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
18
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
19
Hands-on Networking Fundamentals
20
Hands-on Networking
Fundamentals
Chapter 5
Devices for Connecting Networks
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
22
Repeater
• 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
23
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
24
Hands-on Networking Fundamentals
25
Hub
• 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
26
Hands-on Networking Fundamentals
27
Hands-on Networking Fundamentals
28
Bridge
• 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
29
Hands-on Networking Fundamentals
30
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
31
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
32
Router
• 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
33
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
34
Hands-on Networking Fundamentals
35
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
36
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
37
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
38
Switch
• 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
39
Gateway
• 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
40
Hands-on Networking Fundamentals
41
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
42
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
43
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
44
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
45
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
46
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
47