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Because of the speed increases, categorizing networks based on connection speed is outdated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