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Networking FundamentalsKhurram Shahzad. Saudi Arabia +966 50 8654598http://www.facebook.com/khurramshahzad.goraya
Stand-alone computers were insufficient in a business context Hard-drive capacities were insufficientComputers required a local printerSharing documents via the sneakernet was
cumbersomeE-mail didn't exist
Networks addressed these problems
Networking FundamentalsComputer networks allow computers to link
to each other's resourcesNetworks can increase productivity as well as
decrease cash outlay for new hardware and software
Networking FundamentalsNetworking today is a a relatively simple
plug-and-play process Wireless network cards can automatically
detect and join networks Of course, not all networks are that simple
Networking FundamentalsBackground information needed to
understand how networks workLANs vs. WANsPrimary network componentsNetwork operating systems (NOSs)Network resource accessNetwork topologiesNetwork architecturesTransmitting data on a network
LANs vs. WANsLocal area networks (LANs) connect
computers in a single officeWide area networks (WANs) expand the
LANs to include networks outside the local environment
Think of a WAN as multiple, disbursed LANs connected together
LANs exist in many homes (wireless networks) and nearly all businesses
Local Area Networks (LANs)
Local Area Networks (LANs)
Local Area Networks (LANs)The earliest LANs could not cover large
distancesOnly a few software programs supported
themThe first software programs were constrained
by file lockingNowadays, multiple users can access a
program at one time
Wide Area Networks (WANs)
Primary Network ComponentsThree types of components available on a
network:ServersClients or workstationsResources
Blurring the LinesLANs and WANs were often differentiated by
their connection speeds in the 1980s and 90sLANs connected computers with a 10Mbps
connection or faster WANs often connected to each other by very
expensive T1 connections (a maximum bandwidth of 1.544Mbps)
Blurring the LinesToday, connections of 1Gbps are fairly
commonWAN, while still slower than LAN
connectivity, can be several times faster than the T1
Because of the speed increases, categorizing networks based on connection speed is outdated
Today, the most common way to classify a network is based on geographical distance
ServersCore component of the network
Provide a link to the resources needed to perform tasks
Direct client computers Centralize the control of resources and
securityBalance the load on computersCompartmentalize files
ServersPerform several different critical tasks
File serversPrint servers
Can be multipurpose or single-purposeCan be dedicated or nondedicated
Dedicated ServersAssigned to provide specific applications
or services for the network and nothing else
Requires fewer resources from the computer that is hosting it
Savings in overhead may translate to a certain efficiency
A web server is an example of a dedicated server
Nondedicated ServersAssigned to provide one or more network
services and local accessSlightly more flexible in its day-to-day use
than a dedicated serverOften serve as a front-end for the
administrator Can act as a workstation as well as a serverCan function well in a peer-to-peer
environment
Dedicated and NondedicatedMany networks use both dedicated and
nondedicated servers Offers improved network performance and
flexibility
WorkstationsThe computers on which the network users
do their workConnected to a network that offers additional
resourcesCan range from diskless computer systems to
desktop systemsAlso known as client computers
WorkstationsItems needed to make a workstation into a
network clientNetwork interface card (NIC)Special expansion card Cabling system Client software
WorkstationsTo users, being on a network changes a few
things:They can store more informationThey can share and receive information from
other usersThey can use programs that would be too large
or complex for their computerThey can use hardware not attached directly to
their computer
Network ResourcesA resource is any item that can be used on a
networkResources can include
Printers and other peripheralsDisk storage and file accessApplications
Network ResourcesNetworks give users more storage space to
store filesStoring files on a server allows the
administrator to back up user files
Network ResourcesFiles that all users need to access can also be
stored on a server Applications (programs) no longer need to be
on every computer in the office
Being on a Network Brings ResponsibilitiesWhen you are on a network, you need to take
responsibility for your actionsYou cannot randomly delete files or move
documents from server to serverYou do not own your e-mailPrinting does not mean that if you send
something to print it will print immediatelyIf your workstation has also been set up as a
nondedicated server, you cannot turn it off
Network Operating Systems (NOSs)Networks use a NOS to control the
communication with resources and the flow of data across the network
The NOS runs on the serverWith today's NOSs, servers are able to
monitor memory, CPU time, disk space, and peripherals without a babysitter
Network Operating Systems (NOSs)LANs and WANs allow for a wide range of
collaborationNOSs provide this functionality on a network
Network Resource AccessPeer-to-peer and client-serverQuestions to ask
What is the size of the organization?How much security does the company require?What software or hardware does the resource
require?How much administration does it need?How much will it cost?Will this resource meet the needs of the
organization today and in the future?Will additional training be needed?
Peer-to-Peer Networks
Peer-to-Peer NetworksNo centralized administration or control Every station has unique control over the
resources the computer ownsLack of centralized control can make it
difficult to administer the network The network isn't very secureMay not be easy to locate resourcesUsers need more training
Peer-to-Peer NetworksThe right choice for small companies that
don't expect future growthSetting up a peer-to-peer resource model
simply because it is cheap and easy to install could be a costly mistake
Client-Server Resource Model
Client-Server Resource ModelServer-based networks are also known as
domainsThe key characteristic of a domain is that
security is centrally administeredWhen you log in to the network, the login
request is passed to the server responsible for security
In a peer-to-peer model, users need a user account set up on each machine
In a domain, all user accounts are stored on the server
Client-Server Resource ModelThe desired model for companies that are
continually growing or that need to initially support a large environment
Server-based networks offer flexibilityHardware costs may be more, but
managing resources becomes less time consuming
Only a few administrators need to be trained
Users are only responsible for their own work environment
Resource Access ModelAlways take the time to plan your network
before installing itYou don't want the type of network you chose
to not meet the needs of the company
Network TopologiesA way of laying out the networkCan be physical or logicalFive primary topologies
Bus (can be both logical and physical)Star (physical only)Ring (can be both logical and physical)Mesh (can be both logical and physical)Hybrid (usually physical)
Bus Topology
Bus TopologyEasy to install Cheapest to installDifficult to add a workstationExpensive to maintain
Star Topology
Ring Topology
Mesh Topology
Mesh TopologyExpensive to install and maintainThe advantage you gain is high fault
toleranceFound in WANs to connect multiple sites
across WAN linksRouters are used to search multiple
routes through the mesh Becomes inefficient with five or more
entities
Hybrid TopologyA mix of the other topologiesMost networks today are not only hybrid but
heterogeneous May be more expensive, but it exploits the
best features of all the other topologies
Network Topologies
Network ArchitecturesDefine the structure of the network,
including hardware, software, and physical layout
Performance is usually discussed in terms of bandwidth
Major architectures used today are Ethernet and Token Ring
EthernetOriginal definition of the IEEE 802.3 model
included a bus topology using coaxial cable and baseband signaling
From this model came the first Ethernet architecture
Has several specifications, each one specifying the speed, communication method, and cable
Original Ethernet was given a designation of 10Base5
Token RingExactly like the IEEE 802.5 specification Uses a physical star, logical ring topologyWorkstations are cabled to a central device
called a multistation access unit (MAU)Can use shielded or unshielded cable and can
transmit data at either 4Mbps or 16Mbps
Transmitting Data on a NetworkTo facilitate communication across a
network, computers use a common language called a protocol
Protocols are a language with rules that need to be followed so that both computers understand the right communication behavior
Computers need standards to follow to keep their communication OSI modelIEEE 802 standards
OSI ModelThe International Organization for
Standardization (ISO) introduced the Open Systems Interconnection (OSI) model
The ISO put together a seven-layer model providing a relationship between the stages of communication
As transmission takes place data passes through the layers
OSI ModelThe OSI model layers from top to bottom
7. Application layer6. Presentation layer5. Session layer4. Transport layer3. Network layer2. Data Link layer1. Physical layer
OSI ModelApplication layer
Allows access to network servicesThe layer at which file and print services operate
Presentation layer Determines the format of the dataPerforms protocol conversion and manages data
compression, data translation, and encryptionCharacter set information is determined at this
level
OSI ModelSession layer
Allows applications on different computers to establish, maintain, and end a session
Enables network procedures, such as identifying passwords, logons, and network monitoring
Transport layerVerifies that all packets were received by the
destination host on a TCP/IP networkControls the data flow and troubleshoots any
problems with transmitting or receiving datagrams
Provides error checking and reliable, end-to-end communications
OSI ModelNetwork layer
Responsible for logical addressing of messagesAt this layer, the data is organized into chunks
called packetsManages traffic through packet switching,
routing, and controlling congestion of dataData Link layer
Arranges data into chunks called framesDescribes the unique physical address (MAC
address) Subdivided into two sections: Media Access
Control (MAC) and Logical Link Control (LLC)
OSI ModelPhysical layer
Describes how the data gets transmitted over a physical medium
Defines how long each piece of data is and the translation of each into the electrical pulses that are sent over the wires
Decides whether data travels unidirectionally or bidirectionally across the hardware
Relates electrical, optical, mechanical, and functional interfaces to the cable
OSI Model
IEEE 802 StandardsDesigned primarily for enhancements to the
bottom three layers of the OSI modelBreaks the Data Link layer into two sublayers
The LLC sublayer manages data link communications
The MAC sublayer watches out for data collisions and assigns physical addresses
IEEE 802.3 CSMA/CD (Ethernet)Ethernet is the most well-known example
of the IEEE 802.3 CSMA/CD standardThe original 802.3 CSMA/CD standard
Defines a bus topology network that uses a 50 ohm coaxial baseband cable
Carries transmissions at 10MbpsGroups data bits into frames and uses the
CSMA/CD cable access method Currently, the 802.3 standard has been
amended to include speeds up to 10Gbps
IEEE 802.3 CSMA/CD (Ethernet)The CSMA/CD acronym illustrates how it
worksCarrier Sense (CS) means that computers on the
network are listening to the wire at all timesMultiple Access (MA) means that multiple
computers have access to the line at the same time
Collision Detection (CD) detects collisions and senders send again
CSMA/CD technology is considered a contention-based access method
IEEE 802.3 CSMA/CD (Ethernet)The only major downside to 802.3 is that with
large networks (more than 100 computers on the same cable), the number of collisions increases to the point where more collisions than transmissions are taking place
IEEE 802.5 Token RingSpecifies a physical star, logical ring topology
that uses a token-passing technology to put the data on the cable
IBM developed this technology for its mainframe and minicomputer networks
IEEE 802.5 Token RingA chunk of data called a token circulates the
ring A computer with data to transmit takes a
free token off the ring, modifies it, places the token (along with the data) back on the ring
The token travels around the ring The destination computer takes the token
and data off the wire and places the token back on the wire
When the original sender receives the token back, it modifies the token to make it free for use and sends the token back on the ring
IEEE 802.5 Token RingMain advantage of the token-passing access
method is that it eliminates collisionsWhole procedure takes place in a few
millisecondsScales very well
Not uncommon for Token Ring networks based on the IEEE 802.5 standard to reach hundreds of workstations on a single ring
Understanding Networking ProtocolsComputers use a protocol as a common
language for communicationA protocol is a set of rules that govern
communicationsProtocols detail what "language" the
computers are speaking when they talk over a network
If two computers are going to communicate, they both must be using the same protocol
Understanding Networking ProtocolsThe A+ exam objectives list two common
protocols: TCP/IP and NetBIOSOther common protocols
IPX/SPXAppleTalk
TCP/IPMost popular network protocol in use
todayNamed after two of its hardest-working
protocols, Transmission Control Protocol (TCP) and Internet Protocol (IP), but contains dozens of protocols
Protocol of the InternetRobust and flexible Works on disparate operating systems
such as Unix, Linux, and WindowsFlexibility comes from its modular nature
TCP/IP
TCP/IP
TCP/IP
IP AddressesEach device needs to have a unique IP
addressAny device with an IP address is referred to
as a hostConfigure manually or automatically from a
DHCP server
IP AddressesA 32-bit hierarchical address that
identifies a host on the networkTypically written in dotted-decimal
notation, such as 192.168.10.55Each of the numbers represents eight bits (or
one byte) of the address, also known as an octet
The same address written in binary would be 11000000 10101000 00001010 00110111
Numbers will be between 0 and 255
IP AddressesAddresses are said to be hierarchicalNumbers at the beginning of the address
identify groups of computers that belong to the same network
Parts of the IP AddressEach IP address is made up of two
components: the network ID and the host IDNetwork portion comes before the host
portionNetwork portion does not have to be a
specific fixed length
Parts of the IP AddressComputers differentiate where the network
address ends and the host address begins through the subnet maskA value written just like an IP address and may
look something like 255.255.255.0Any bit that is set to a 1 in the subnet mask
makes the corresponding bit in the IP address part of the network address
The number 255 is the highest number you will ever see in IP addressing, and it means that all bits in the octet are set to 1
Parts of the IP AddressAn example
The subnet mask of 255.255.255.0 indicates that the first three octets are the network portion of the address, and the last octet is the host portion
In the IP address of 192.168.10.55, the network portion is 192.168.10 and the host portion is 55
IP Address ClassesClasses of networks are based on their
sizeClass A - huge companies with thousands of
computersClass C - companies with few computersClass B - medium-sized companiesClass D and E - reserved
The class of address can be identified by the first octet of the IP address
Class A
Designed for very large networks Default network portion for Class A
networks is the first 8 bitsOnly 126 Class A network addresses
availableRemaining 24 bits of the address allow
each Class A network to hold as many as 16,777,214 hosts
All possible Class A networks are in use; no more are available
Class BDesigned for medium-sized networksDefault network portion for Class B networks
is the first 16 bitsAllows for 16,384 networks, each with as
many as 65,534 hosts attachedClass B networks are generally regarded as
unavailable
Class CDesigned for smaller networksDefault network portion for Class C
networks is the first 24 bitsAllows for 2,097,152 networks, but each
network can have a maximum of only 254 hosts
Most companies have Class C network addresses
Class C networks are still available
IP Address Classes
Common PortsEach protocol in the TCP/IP suite that
operates at the Process/Application layer uses a port number to identify information it sends or receives
The port number, when combined with the host's IP address, is called a socket
Common Ports65,536 ports numbered from 0 to 65535Ports 0 through 1023 are called the well-
known ports1024 through 49151 are called the registered
portsAnything from 49152 to 65535 is free to be
used by application vendors
Common Ports
DHCP and DNSBoth are run off a server and provide key
services to network clientsA DHCP server can be configured to
automatically provide IP configuration information to clientsIP addressSubnet maskDefault gateway (the "door" to the outside
world)DNS server address
DHCP and DNSDNS resolves hostnames to IP addresses
Allows your computer to get the address of the website you want and traverse the Internet to find it
DHCP and DNSDNS works the same way on an intranetInstead of helping you find google.com, it
may help you find Jenny's print server or Joe's file server
Other ProtocolsThere probably aren't any reasons why you
would want to use a different protocolOnly knock on TCP/IP is that it can be more
difficult to configure than other protocolsOnly other protocol called out on the A+
Essentials exam objectives is NetBIOS
NetBEUI/NetBIOSNetBIOS is an acronym formed from network
basic input/output systemIs a Session layer network protocol Provides an interface with a consistent set of
commands for requesting lower-level network services to transmit information from node to node
NetBEUI/NetBIOSNetBEUI is an acronym formed from
NetBIOS Extended User InterfaceAn implementation and extension of IBM's
NetBIOS transport protocol from MicrosoftShipped with all versions of Microsoft's
operating systems and is generally considered to have a lot of overhead
Has no networking layer and therefore no routing capability
NetBEUI/NetBIOSThese protocols make up a very fast
protocol suite that most people call NetBEUI/NetBIOS
Good for small LANs Allows users to find and use the network
services they need easilyBecause it contains no Network layer
protocol, it cannot be routed and thus cannot be used on a WAN
IPX/SPXDefault communication protocol for versions
of the Novell NetWare operating system before NetWare 5
A communication protocol similar to TCP/IPUsed primarily in LANsTwo main protocols in IPX/SPX are IPX and
SPXSPX provides similar functions to TCPIPX provides functions similar to the TCP/IP suite
protocols IP and UDP
IPX/SPX
AppleTalkNot just a protocol - it is a proprietary
network architecture for Macintosh computers
Uses a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) technology to put data on the cable
Unlike Ethernet, which uses a CSMA/CD method (where the CD stands for Collision Detection), it uses smart interface cards to detect traffic before it tries to send data
A CSMA/CA card listens to the wire
AppleTalkBig selling point of AppleTalk
Simple and cheapCame installed on Macintosh computersAssigned itself an address
ProblemsSlowLimited in capacity Had to license it from Apple
Today, TCP/IP is the default networking protocol on Macs
Network Interface Cards (NICs)Physical interface between computer and
cablingPrepares, sends, and controls flow of dataConsiderations when choosing a NIC
Preparing dataSending and controlling dataConfigurationDriversCompatibilityPerformance
Preparing DataIn the computer, data moves along buses in
parallelThe NIC translates the data from the
computer into signals that can flow easily along the cable
It translates digital signals into electrical signals (and in the case of fiber-optic NICs, to optical signals)
Sending and Controlling DataFor two computers to send and receive
data, the cards must agree on several thingsMaximum size of the data framesAmount of data sent before giving confirmationTime needed between transmissionsAmount of time to wait before sending
confirmationAmount of data a card can holdSpeed at which data transmits
Sending and Controlling DataTo successfully send data on the network, all
NICs need to use the same media access method
If you try to use cards of different types neither of them would be able to communicate with the other unless you had a separate hardware device between them that could translate
Sending and Controlling DataNICs can send data using either full-
duplex or half-duplex modeHalf-duplex means that between the sender
and receiver, only one can transmit at any one time
In full-duplex communication, a computer can send and receive data simultaneously
Main advantage of full-duplex over half-duplex communication is performance
NICs can operate twice as fast (200Mbps) in full-duplex mode as they do normally in half-duplex mode (100Mbps)
NIC ConfigurationThe NIC's configuration may include
Manufacturer's hardware addressIRQ addressBase I/O port addressBase memory address
Each card must have a unique MAC address
If two cards on the same network have the same MAC address, neither one will be able to communicate
IEEE has established a standard for hardware addresses
NIC DriversFor the computer to use the NIC, it is very
important to install the proper device driversDrivers communicate directly with the
network redirector and adapterOperate in the Media Access Control
sublayer of the Data Link layer of the OSI model
PC Bus TypeChoose NIC that fits the bus type of your PCIf you have more than one type of bus in your
PC use a NIC that fits into the fastest type More and more computers are using network
cards that have either PC Card or USB interfaces
Network Interface Card PerformanceMost important goal of the network adapter
card is to optimize network performance and minimize the amount of time needed to transfer data packets across the network
Ensure you get the fastest card you can for the type of network you're on
Cabling and ConnectorsCable properly moves the data to its intended
destinationFour main types of cabling methods
Coaxial cableTwisted-pair cableFiber-optic cableWireless
Coaxial
CoaxialAvailable in various specifications that are
rated according to the RG Type systemDistance and cost are considerations when
selecting coax cableThe thicker the copper, the farther a signal can
travel -- and with that comes a higher cost and a less-flexible cable
Coaxial
Coax Connector Types
Coax Connector Types
Twisted Pair
Twisted PairCategory 1: voice-only transmissions, two twisted
pairsCategory 2: 4Mbps, four twisted pairsCategory 3: 10Mbps, four twisted pairs Category 4: 16Mbps, four twisted pairs Category 5: 100Mbps, four twisted pairs of
copper wire Category 5e: up to 1Gbps, four twisted pairs of
copper wire, but they are physically separated and contain more twists per foot than Category 5
Category 6: up to 1Gbps and beyond, four twisted pairs of copper wire, and they are oriented differently than in Category 5 or 5e
Twisted-Pair Connector Types
Twisted-Pair Connector Types
Fiber-Optic
Fiber-OpticReferred to as either single-mode or
multimode fiberMode refers to the bundles of light that
enter the fiber-optic cableSingle-mode
Uses only a single mode of light to propagateMultimode
Allows multiple modes of light to propagateLight bounces off the cable walls as it travels
through the cable, which causes the signal to weaken more quickly
Fiber-OpticMultimode
Most often used as horizontal cablePermits multiple modes of light to propagate
through the cable, which shortens cable distances and delivers a less available bandwidth
Devices that use multimode fiber-optic cable typically use light-emitting diodes (LEDs)
Higher bandwidth network devices such as Gigabit Ethernet are now using lasers with multimode fiber-optic cable
ANSI/TIA/EIA-568-B recognizes two-fiber (duplex) 62.5/125 micron multimode fiber; ANSI/TIA/EIA-568-B also recognizes 50/125 micron multimode fiber-optic cable
Fiber-OpticSingle-mode
Used as backbone cabling and in phone systemsLight travels straight down the fiber and does not
bounce off the cable wallsSupports higher bandwidth and longer distances Devices that use single-mode typically use lasers to
generate the light that travels through the cableANSI/TIA/EIA-568-B recognizes 62.5/125 micron,
50/125 micron, 8.3/125 micron single-mode optical fiber cables
Maximum backbone distance using single-mode is 3,000 meters; maximum backbone distance using multimode is 2,000 meters
Fiber-Optic Connector Types
Fiber-Optic Connector Types
Wireless NetworksOffer the ability to extend a LAN without the
use of traditional cabling methodsTransmissions are made through the air by
infrared light, laser light, narrow-band radio, microwave, or spread-spectrum radio
Most often in environments where standard cabling methods are not possible or wanted
Not as fast or efficient as standard cabling methods
More susceptible to eavesdropping and interference than standard cabling methods
Networking ComponentsConnectivity devices
Allow communications to break the boundaries of local networks
Let your computers talk to other computers in the next building, the next city, or the next country
Networking ComponentsThere are several categories of
connectivity devicesRepeatersHubsSwitchesBridgesRouters
Make it possible to lengthen networks to almost unlimited distances
RepeatersAllow a cabling system to extend beyond its
maximum allowed length by amplifying the network voltages
Very inexpensiveOperate at the Physical layer of the OSI
modelOnly used to regenerate signals between
similar network segmentsMain disadvantage is that they just amplify
signalsNot only network signals but any noise on the wireUsed only as a temporary fix
HubsUsed to link several computers togetherMost often used on Ethernet networksJust multiport repeaters and work at Layer 1
of the OSI model just as repeaters doRepeat any signal that comes in on one port
and copy it to the other ports (a process that is also called broadcasting)
HubsTwo types of hubs
Passive Hubs Connect all ports together electrically Do not have their own power source
Active hubs Use electronics to amplify and clean up the signal
before it is broadcast to the other ports Includes a class called intelligent hubs, which can
be remotely managed on the network
SwitchesProvide centralized connectivity just as
hubs do (usually on twisted-pair Ethernet networks); often look similar, so it's easy to confuse them
Switches examine the Layer 2 header of the incoming packet and forward it properly to the right port and only that port
Greatly reduces overhead and thus performance as there is essentially a virtual connection between sender and receiver
Indicator LightsNearly every hub or switch has one or
more status indicator lightsIf there is a connection to that port of the
switch, a light will light upIf traffic is crossing the port, the light may
flash, or there may be a secondary lightMany devices can also detect a problem in
the connectionBridges and routers will also have similar
status lights on them, as do network cards
BridgesOperate in the Data Link layer of the OSI modelJoin similar topologies and used to divide network
segmentsKeep traffic on one side from crossing to the
otherOften used to increase performance on a high-
traffic segmentNot able to distinguish one protocol from
another, because higher levels of the OSI model are not available to them
If a bridge is aware of the destination MAC address, it can forward packets; otherwise, it forwards the packets to all segments
BridgesMore intelligent than repeatersUnable to move data across multiple
networks simultaneouslyMain disadvantage is that they forward
broadcast packetsBroadcasts are addressed to all computers, so
the bridge just does its job and forwards the packets
Cannot perform intelligent path selection
RoutersHighly intelligent devices that connect multiple
network types Route packets across multiple networksUse routing tables to store network addresses Operate at the Network layer of the OSI modelCan determine the best path for data to take to
get to its destinationLike bridges, they can segment large networksSlower than bridges because they analyze every
packetMore expensive
RoutersNormally used to connect one LAN to
anotherTypically, when a WAN is set up, at least two
routers are usedWireless routers have become all the rage for
small and home networksPossess all of the functionality of routers
historically associated with networking, but they are relatively inexpensive
Wired NetworksA network where you are using a cable to
plug into a socket in the wall or a connectivity device on your table
Historically, using wires was the only way to connect several machines together
Today, wired options are becoming few and far between
Two broad categories of choices to get onlineDial-upBroadband
Dial-upOne of the oldest ways of communicating
with ISPs and remote networks Not used much anymore due to limitations
on modem speed, which top out at 56KbpsCannot compare to speeds possible with
DSL and cable modemsDial-up Internet connections dropped
from 74 percent in 2000 to 15 percent in 2008Most of the people who still use dial-up do it
because it's cheaper than broadband or high-speed isn't available where they live
Dial-upBiggest advantage to dial-up is that it's cheap
and relatively easy to configureCompanies can grant users dial-up access to
their networksISPs and RAS servers would use the Data
Link layer Point-to-Point Protocol (PPP) to establish and maintain the connection
BroadbandA connection that is capable of transmitting
multiple pieces of data simultaneously in order to achieve higher data rates
The opposite of broadband is basebandSeveral different types of broadband Internet
access are available, including DSL, Cable, fiber-optic, and satellite
DSL
DSLThere are several different forms of DSL,
includingHigh bit-rate DSL (HDSL)Symmetric DSL (SDSL)Very high bit-rate DSL (VDSL)Rate-adaptive DSL (RADSL)Asymmetric DSL (ADSL)
The most popular in home use is ADSLIt's asymmetrical because it supports faster
download speeds than upload speeds
DSL
DSLFirst ADSL standard was approved in 1998
and offered maximum download speeds of 8Mbps and upload speeds of 1Mbps
The newest standard supports speeds up to 24Mbps download and 3.5Mbps upload
Most ADSL communications are full-duplex
One major advantage that ADSL providers tout is that with DSL you do not share bandwidth with other customers
Cable ModemProvides high-speed Internet access
through your cable serviceYou plug your computer into the cable
modem using a standard Ethernet cableIn theory, cable Internet connections are
faster than DSL connectionsDownload speeds up to 30Mbps or 50Mbps and
uploads of 5MbpsA caveat to these speeds is that they are not
guaranteed and they can vary
Cable ModemSpeeds vary because you are sharing
available bandwidth within your distribution network
Size of the network is usually between 100 and 2,000 customers
Access can be slower during peak usage times
Cable ModemA simplified example
Two users are sharing a connection that has a maximum capacity of 40Mbps
Each person gets 20Mbps of bandwidthOne user gets a boost that allows her to
download 30MbpsThe other user is left with 10Mbps of available
bandwidth
Cable ModemIn practice, the speeds of a cable modem
are pretty comparable to those of DSLBoth have pros and cons when it comes to
reliability and speed of serviceA lot varies by service provider and isn't
necessarily reflective of the technologyThe choice you make between DSL and
cable may depend on which company you get the best package deal from
Fiber-Optic CableUsed mostly for high-speed
telecommunications and network backbonesMuch more expensive than copper to install
and operateSome phone and media companies are now
offering fiber-optic Internet connections for home subscribers
Fiber-Optic CableFiber-to-the-Home (FTTH) service
As of the time of this writing, the fastest speeds offered are 50Mbps download and 20Mbps upload
FTTH is capable of reaching speeds of 100Mbps, and 400Mbps implementations are being planned
Fiber-to-the-Node (FTTN)Runs fiber to the phone or cable company's utility
box near the street and then runs copper from there to your house
Maximum speeds for this type of service are around 25Mbps
SatelliteTransmits signals through the air to you as
opposed to using a cableService provider beams a microwave signal from
a dish on the ground to an orbiting satellite, which in turn sends the signal back down to your receiver
Receivers are typically small satellite dishes but can also be portable satellite modems or portable satellite phones
Called point-to-multipoint because one satellite can provide a signal to a number of receivers
Used in a variety of applications from telecommunications to handheld GPSs to television and radio broadcasts
SatelliteConsiderations to keep in mind regarding
satelliteInstallation can be trickyLine of sight is required
SatelliteMore considerations
Latency can be a problemConnections are pretty slow
Wireless NetworksAs a technician, you must make sure that
their computers can connect Four methods of wireless communication
802.11xBluetoothCellularInfrared
802.11xWLAN standards are created and managed
by the IEEEMost commonly used WLAN standards used
today are in the IEEE 802.11x familyIEEE 802.11 was ratified in 1997, and was
the first standardized WLAN implementationOver twenty 802.11 standards defined, but
you will only see a few in common operation: 802.11a, b, and g
Among all of the wireless technologies covered, 802.11 is the one best suited for WLANs
802.11x NetworksJust like an Ethernet network, only wirelessAt the center of the network is a connectivity
device such as a hub or a router, and all computers connect to it
In order to connect to the wireless hub or router, the client needs to know the SSID of the device
Wireless access points eventually connect back to a wired connection with the rest of the network
802.11x Technical Specifications802.11x networks use the CSMA/CA access
methodSimilar to that of shared EthernetPacket collisions are generally avoidedIf they do happen, the sender waits a random
period of time (called a back-off time) before transmitting again
802.11x Technical Specifications802.11
Defines WLANs transmitting at 1Mbps or 2Mbps bandwidths using the 2.4GHz frequency spectrum
Uses FHSS or DSSS for data encoding802.11a
Provides WLAN bandwidth of up to 54Mbps in the 5GHz frequency spectrum
Uses OFDM, rather than FHSS or DSSSNever gained widespread popularity because
802.11b devices were significantly cheaper and it's highly susceptible to external interference
802.11x Technical Specifications802.11b
Provides for bandwidths of up to 11Mbps in the 2.4GHz frequency spectrum
Also called WiFi or 802.11 high rateUses DSSS for data
802.11gProvides for bandwidths of 54Mbps+ in the 2.4GHz
frequency spectrumUses OFDM encodingIs backward compatible with 802.11b
Some devices marked as 802.11b/g that can run on either network, and can be commingled on the same network
802.11x Technical SpecificationsInteroperability concerns
Not capable of understanding OFDM transmissions
To counteract this problem, uses an additional signaling mechanism RTS/CTS to provide backward compatibility The client must first send an RTS signal to the access
point Once the access point sends a CTS back to the client,
the client can transmit Other clients interpret the CTS signal, they interpret it
as a "do not send" message and wait for an all-clear to send
802.11x Technical SpecificationsMore interoperability concernsWhen operating in mixed mode, 802.11g will
use the less-efficient 802.11b back-off timingSlows down the throughput of the 802.11g
access pointThe pros of 802.11g/b backward
compatibility still far outweigh the cons
802.11x Technical Specifications802.11n
At the time of this writing, still in development Provides bandwidths from 54Mbps to
600Mbps, but more realistic to expect maximum throughput in the 300Mbps range
Achieves faster throughput a couple of ways MIMO Channel bonding SDM technologies
802.11x Technical Specifications802.11n is backward compatible with
802.11a/b/g802.11n hardware is on the market today,
but as the standard is still not official these devices are called "pre-N" devices May have compatibility issues between
different vendors' pre-N products
802.11x Technical Specifications
802.11x Technical SpecificationsSignal modulation techniques used in the
802.11 standardsDirect-Sequence Spread Spectrum (DSSS) Frequency-Hopping Spread Spectrum (FHSS) Orthogonal Frequency Division Multiplexing
(OFDM)
802.11x Devices
802.11x SecurityThe growth of wireless systems has created
several opportunities for attackersUsing SSID configurations doesn't
necessarily prevent wireless networks from being compromised
WEPA security standard for wireless devicesEncrypts data to provide data securityHas always been under scrutiny for not being
as secure as initially intended
WEPVulnerable due to weaknesses in the
encryption algorithmsThis makes WEP one of the more vulnerable
protocols available for security
WPAAn improvement on WEP that was developed
in 2003Implements some of the standards defined in
the IEEE 802.11i specificationImprovement over WPA is WPA2, which
implements the full 802.11i standard
MAC FilteringCan be used on a wireless network to prevent
certain clients from accessing the networkYou tell your wireless router to only allow
access to certain MAC addressesYour router will allow you to deny service to a
set list of MAC addresses (and allow all others) or allow service only to a set of MAC addresses (and deny all others)
BluetoothMakers of Bluetooth were trying to unite
disparate technology industriesFirst Bluetooth device arrived on the
scene in 2000By 2002, there were over 500 Bluetooth
certified productsAs of 2005 over 5 million Bluetooth
chipsets shipped each weekCurrent Bluetooth specification is Version
2.1+ Enhanced Data Rate
Bluetooth Networks"Bluetooth wireless technology is a short-range
communications technology intended to replace the cables connecting portable and/or fixed devices while maintaining high levels of security."
Operates at low power and low cost and can handle simultaneous voice and data transmissions
One of the unusual features of Bluetooth networks is their temporary natureThis dynamically created network is called a piconetA Bluetooth-enabled device can communicate with up to
seven other devices in one piconet
Bluetooth NetworksWithin the piconet, one device is the master
and the other seven devices are slavesCommunication can occur only between the
master and a slaveRole of master rotates quickly among the devices
in a round-robin fashionAll devices in a piconet can communicate with
each other directlyCurrent Bluetooth specifications allow for
connecting two or more piconets together in a scatternet
Bluetooth Technical Specifications Version 1.2
Adopted in November 2003Supports data transmissions of up to 1Mbps
Version 2.0+ Enhanced Data Rate (EDR)Adopted in November 2004Supports data rates up to 3Mbps
Version 2.1+EDRAdopted in July 2007Supports data rates up to 3Mbps
All standards transmit in the 2.4-2.485GHz range
Bluetooth Technical Specifications
Bluetooth DevicesThe first device was a wireless headset for
a cell phoneBluetooth-enabled computer peripherals
includeKeyboards and micePrintersDigital camerasMP3 playersPDAs and handheld computersCars
Bluetooth Devices
Bluetooth Devices
InfraredLonger than light waves but shorter than
microwavesMost common use of infrared technology is
the television remote control"Walk-up" and "point-to-point"
You need to be at very close range Designed for one-to-one communicationRequires line of sight
Infrared
Infrared NetworksA point-to-point network between two devicesNo master or slaveNo hub-type device requiredPoint one infrared-enabled device at another
and transmit
Infrared Technical SpecificationsCurrent IrDA specifications allow
transmission of data up to 16Mbps and IrDA claims that 100Mbps and 500Mbps standards are on the horizon
No concerns of interference or signal conflicts
Atmospheric conditions can play a role in disrupting infrared waves
Security is not an issue Data is directional, and you choose when and
where to send it
Infrared DevicesMiceKeyboardsPrintersKeyboards for PDAsPDAsCell phonesRemote control
Cellular (Cellular WAN)Industry has revolutionized the way we
communicatePrimarily been developing in the realm of
small handheld communications devices (phones and the BlackBerrys)
Converging technologies -- cell phones and computers
Cellular NetworksVery complex behind the scenesCell communications require the use of a
central access point, generally a cell tower, which is connected to a main hub
Very large mesh networks with extensive range
Cellular Technical SpecificationsTwo major cell standards in the United
States: GSM and CDMANot compatible with each other
GSM uses a variety of bands to transmitMost popular are 900MHz and 1800MHz400, 450, and 850MHz are also used
GSM splits up its channels by time division, in a process called Time Division Multiple Access (TDMA)
Cellular Technical SpecificationsMaximum rate for GSM is about 270
kilobits per second (Kbps) Maximum functional distance of GSM is
about 22 miles (35 kilometers)For security, GSM uses the A5/1 and A5/2
stream ciphersNewer enhancement to GSM is called
General Packet Radio Service (GPRS)Designed to provide data transmissions over a
GSM network at up to 171Kbps
Cellular Technical SpecificationsCDMA is considered a superior technology to GSMDoesn't break up its channels by time but rather by
a code inserted into the communicated messageTransmissions to occur at the same time without
interferenceUsed in GPSsCDMA supports download rates of over 3Mbps,
with upload speeds of nearly 2MbpsWorks in ranges up to 100 kilometersNewer takeoffs of the CDMA technology include W-
CDMA, CDMA2000, and EVDO
Cellular DevicesFurther developed in the phone industry than
the computer industryCell phones and BlackBerrys are the most
common cellular-equipped devices Cellular modems are widely available for
laptops, most of them with a PC Card interface
Virtual Private Networks (VPNs)Not necessarily wired or wirelessNot a LAN or a WAN but rather something in
betweenMakes computers that are on opposite sides
of a WAN link think they are on the same safe and secure LAN with each other
The key word for VPNs really is security
Virtual Private Networks (VPNs)Device that provides VPN service is called a
VPN concentratorCreate virtual private networks for users
logging in using remote access or for a large site-to-site VPN
VPNs provide higher data throughput and authentication and encryption options