networking comptia

Networking Fundamentals

Stand-alone computers were insufficient in a business context

Hard-drive capacities were insufficient

Computers required a local printer

Sharing documents via the sneakernet was cumbersome

E-mail didn't exist

Networks addressed these problems


Computer networks allow computers to link to each other's resources

Networks can increase productivity as well as decrease cash outlay for new hardware and software


Networking 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


Background information needed to understand how networks work

LANs vs. WANsPrimary network componentsNetwork operating systems (NOSs)Network resource accessNetwork topologiesNetwork architecturesTransmitting data on a network

LANs vs. WANs

Local area networks (LANs) connect computers in a single office

Wide 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)

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 Components

Three types of components available on a network:

Servers

Clients or workstations

Resources

Blurring the Lines

LANs and WANs were often differentiated by their connection speeds in the 1980s and 90s

LANs 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 Lines

Today, connections of 1Gbps are fairly common

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Because of the speed increases, categorizing networks based on connection speed is outdated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

Servers

Core component of the networkProvide a link to the resources needed to perform tasks

Direct client computers

Centralize the control of resources and security

Balance the load on computers

Compartmentalize files

Servers

Perform several different critical tasksFile servers

Print servers

Can be multipurpose or single-purpose

Can be dedicated or nondedicated

Dedicated Servers

Assigned 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 Servers

Assigned to provide one or more network services and local access

Slightly more flexible in its day-to-day use than a dedicated server

Often serve as a front-end for the administrator

Can act as a workstation as well as a server

Can function well in a peer-to-peer environment

Dedicated and Nondedicated

Many networks use both dedicated and nondedicated servers

Offers improved network performance and flexibility

Workstations

The computers on which the network users do their work

Connected to a network that offers additional resources

Can range from diskless computer systems to desktop systems

Also known as client computers

Workstations

Items needed to make a workstation into a network client

Network interface card (NIC)

Special expansion card

Cabling system

Client software

Workstations

To 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 Resources

A resource is any item that can be used on a network

Resources can include Printers and other peripherals

Disk storage and file access

Applications

Network Resources

Networks give users more storage space to store files

Storing files on a server allows the administrator to back up user files

Network Resources

Files 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 Responsibilities

When you are on a network, you need to take responsibility for your actions

You 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 server

With 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 collaboration

NOSs provide this functionality on a network

Network Resource Access

Peer-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


No 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


The right choice for small companies that don't expect future growth

Setting 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


Server-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 securityIn a peer-to-peer model, users need a user account set up on each machineIn a domain, all user accounts are stored on the server


The desired model for companies that are continually growing or that need to initially support a large environmentServer-based networks offer flexibilityHardware costs may be more, but managing resources becomes less time consumingOnly a few administrators need to be trainedUsers are only responsible for their own work environment

Resource Access Model

Always take the time to plan your network before installing it

You don't want the type of network you chose to not meet the needs of the company

Network Topologies

A 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 Topology

Easy to install

Cheapest to install

Difficult to add a workstation

Expensive to maintain

Star Topology

Ring Topology

Mesh Topology

Mesh Topology

Expensive to install and maintain

The advantage you gain is high fault tolerance

Found in WANs to connect multiple sites across WAN links

Routers are used to search multiple routes through the mesh

Becomes inefficient with five or more entities

Hybrid Topology

A mix of the other topologies

Most 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 Architectures

Define 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

Ethernet

Original 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 Ring

Exactly 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 Network

To facilitate communication across a network, computers use a common language called a protocolProtocols are a language with rules that need to be followed so that both computers understand the right communication behaviorComputers need standards to follow to keep their communication

OSI modelIEEE 802 standards

OSI Model

The 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 Model

The OSI model layers from top to bottom 7. Application layer

6. Presentation layer

5. Session layer

4. Transport layer

3. Network layer

2. Data Link layer

1. Physical layer

OSI Model

Application layerAllows access to network services

The layer at which file and print services operate

Presentation layer Determines the format of the data

Performs protocol conversion and manages data compression, data translation, and encryption

Character set information is determined at this level

OSI Model

Session layerAllows applications on different computers to establish, maintain, and end a sessionEnables 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 datagramsProvides error checking and reliable, end-to-end communications

OSI Model

Network 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 data

Data Link layerArranges 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 Model

Physical layerDescribes 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 Standards

Designed primarily for enhancements to the bottom three layers of the OSI model

Breaks 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 10Mbps

Groups 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


The CSMA/CD acronym illustrates how it worksCarrier Sense (CS) means that computers on the network are listening to the wire at all times

Multiple 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


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 Ring

Specifies 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


A 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 ringThe token travels around the ring The destination computer takes the token and data off the wire and places the token back on the wireWhen 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


Main 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 Protocols

Computers use a protocol as a common language for communication

A protocol is a set of rules that govern communicationsProtocols detail what "language" the computers are speaking when they talk over a networkIf two computers are going to communicate, they both must be using the same protocol

Understanding Networking Protocols

The A+ exam objectives list two common protocols: TCP/IP and NetBIOS

Other common protocolsIPX/SPX

AppleTalk

TCP/IP

Most 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

IP Addresses

Each device needs to have a unique IP address

Any device with an IP address is referred to as a host

Configure manually or automatically from a DHCP server

IP Addresses

A 32-bit hierarchical address that identifies a host on the network

Typically written in dotted-decimal notation, such as 192.168.10.55

Each 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 Addresses

Addresses are said to be hierarchical

Numbers at the beginning of the address identify groups of computers that belong to the same network

Parts of the IP Address

Each IP address is made up of two components: the network ID and the host ID

Network portion comes before the host portion

Network portion does not have to be a specific fixed length


Computers differentiate where the network address ends and the host address begins through the subnet mask

A 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 addressThe 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


An exampleThe 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 portionIn the IP address of 192.168.10.55, the network portion is 192.168.10 and the host portion is 55

IP Address Classes

Classes 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 hostsAll possible Class A networks are in use; no more are available

Class B

Designed for medium-sized networks

Default network portion for Class B networks is the first 16 bits

Allows for 16,384 networks, each with as many as 65,534 hosts attached

Class B networks are generally regarded as unavailable

Class C

Designed for smaller networks

Default network portion for Class C networks is the first 24 bits

Allows 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 Ports

Each 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 Ports

65,536 ports numbered from 0 to 65535

Ports 0 through 1023 are called the well-known ports

1024 through 49151 are called the registered ports

Anything from 49152 to 65535 is free to be used by application vendors

Common Ports

DHCP and DNS

Both are run off a server and provide key services to network clients

A DHCP server can be configured to automatically provide IP configuration information to clients

IP address

Subnet mask

Default gateway (the "door" to the outside world)

DNS server address

DHCP and DNS

DNS 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 DNS

DNS works the same way on an intranet

Instead of helping you find google.com, it may help you find Jenny's print server or Joe's file server

Other Protocols

There probably aren't any reasons why you would want to use a different protocol

Only knock on TCP/IP is that it can be more difficult to configure than other protocols

Only other protocol called out on the A+ Essentials exam objectives is NetBIOS

NetBEUI/NetBIOS

NetBIOS is an acronym formed from network basic input/output system

Is 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/NetBIOS

NetBEUI is an acronym formed from NetBIOS Extended User Interface

An implementation and extension of IBM's NetBIOS transport protocol from Microsoft

Shipped 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/NetBIOS

These 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 easily

Because it contains no Network layer protocol, it cannot be routed and thus cannot be used on a WAN

IPX/SPX

Default communication protocol for versions of the Novell NetWare operating system before NetWare 5

A communication protocol similar to TCP/IP

Used primarily in LANs

Two main protocols in IPX/SPX are IPX and SPXSPX provides similar functions to TCP

IPX provides functions similar to the TCP/IP suite protocols IP and UDP

IPX/SPX

AppleTalk

Not just a protocol - it is a proprietary network architecture for Macintosh computersUses a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) technology to put data on the cableUnlike 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 dataA CSMA/CA card listens to the wire

AppleTalk

Big 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 Data

In the computer, data moves along buses in parallel

The 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 Data

For two computers to send and receive data, the cards must agree on several things

Maximum size of the data frames

Amount of data sent before giving confirmation

Time needed between transmissions

Amount of time to wait before sending confirmation

Amount of data a card can hold

Speed at which data transmits


To 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


NICs can send data using either full-duplex or half-duplex mode

Half-duplex means that between the sender and receiver, only one can transmit at any one timeIn full-duplex communication, a computer can send and receive data simultaneouslyMain advantage of full-duplex over half-duplex communication is performanceNICs can operate twice as fast (200Mbps) in full-duplex mode as they do normally in half-duplex mode (100Mbps)

NIC Configuration

The NIC's configuration may includeManufacturer's hardware addressIRQ addressBase I/O port addressBase memory address

Each card must have a unique MAC addressIf two cards on the same network have the same MAC address, neither one will be able to communicateIEEE has established a standard for hardware addresses

NIC Drivers

For the computer to use the NIC, it is very important to install the proper device drivers

Drivers communicate directly with the network redirector and adapter

Operate in the Media Access Control sublayer of the Data Link layer of the OSI model

PC Bus Type

Choose NIC that fits the bus type of your PC

If 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 Performance

Most 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 Connectors

Cable properly moves the data to its intended destination

Four main types of cabling methodsCoaxial cable

Twisted-pair cable

Fiber-optic cable

Wireless

Coaxial

Coaxial

Available in various specifications that are rated according to the RG Type system

Distance and cost are considerations when selecting coax cable

The 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

Twisted Pair

Twisted Pair

Category 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 5Category 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

Fiber-Optic

Fiber-Optic

Referred 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-Optic

MultimodeMost often used as horizontal cablePermits multiple modes of light to propagate through the cable, which shortens cable distances and delivers a less available bandwidthDevices 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 cableANSI/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-Optic

Single-modeUsed 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

Wireless Networks

Offer 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 radioMost often in environments where standard cabling methods are not possible or wantedNot as fast or efficient as standard cabling methodsMore susceptible to eavesdropping and interference than standard cabling methods

Networking Components

Connectivity devicesAllow 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 Components

There are several categories of connectivity devices

Repeaters

Hubs

Switches

Bridges

Routers

Make it possible to lengthen networks to almost unlimited distances

Repeaters

Allow 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 signals

Not only network signals but any noise on the wireUsed only as a temporary fix

Hubs

Used to link several computers together

Most often used on Ethernet networks

Just multiport repeaters and work at Layer 1 of the OSI model just as repeaters do

Repeat any signal that comes in on one port and copy it to the other ports (a process that is also called broadcasting)

Hubs

Two types of hubsPassive 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

Switches

Provide 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 Lights

Nearly every hub or switch has one or more status indicator lights

If 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 light

Many devices can also detect a problem in the connectionBridges and routers will also have similar status lights on them, as do network cards

Bridges

Operate 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 themIf a bridge is aware of the destination MAC address, it can forward packets; otherwise, it forwards the packets to all segments

Bridges

More intelligent than repeatersUnable to move data across multiple networks simultaneouslyMain disadvantage is that they forward broadcast packets

Broadcasts are addressed to all computers, so the bridge just does its job and forwards the packetsCannot perform intelligent path selection

Routers

Highly 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

Routers

Normally 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 networks

Possess all of the functionality of routers historically associated with networking, but they are relatively inexpensive

Wired Networks

A network where you are using a cable to plug into a socket in the wall or a connectivity device on your tableHistorically, using wires was the only way to connect several machines togetherToday, wired options are becoming few and far betweenTwo broad categories of choices to get online

Dial-upBroadband

Dial-up

One 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 2008

Most 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-up

Biggest advantage to dial-up is that it's cheap and relatively easy to configure

Companies can grant users dial-up access to their networks

ISPs and RAS servers would use the Data Link layer Point-to-Point Protocol (PPP) to establish and maintain the connection

Broadband

A connection that is capable of transmitting multiple pieces of data simultaneously in order to achieve higher data rates

The opposite of broadband is baseband

Several different types of broadband Internet access are available, including DSL, Cable, fiber-optic, and satellite

DSL

There are several different forms of DSL, including

High 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

First 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 Modem

Provides 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 connections

Download 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 Modem

Speeds 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 Modem

A simplified example Two users are sharing a connection that has a maximum capacity of 40Mbps

Each person gets 20Mbps of bandwidth

One user gets a boost that allows her to download 30Mbps

The other user is left with 10Mbps of available bandwidth

Cable Modem

In practice, the speeds of a cable modem are pretty comparable to those of DSL

Both have pros and cons when it comes to reliability and speed of service

A lot varies by service provider and isn't necessarily reflective of the technology

The choice you make between DSL and cable may depend on which company you get the best package deal from

Fiber-Optic Cable

Used mostly for high-speed telecommunications and network backbones

Much more expensive than copper to install and operate

Some phone and media companies are now offering fiber-optic Internet connections for home subscribers

Fiber-Optic Cable

Fiber-to-the-Home (FTTH) serviceAs of the time of this writing, the fastest speeds offered are 50Mbps download and 20Mbps uploadFTTH 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 houseMaximum speeds for this type of service are around 25Mbps

Satellite

Transmits 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 receiverReceivers are typically small satellite dishes but can also be portable satellite modems or portable satellite phonesCalled point-to-multipoint because one satellite can provide a signal to a number of receiversUsed in a variety of applications from telecommunications to handheld GPSs to television and radio broadcasts

Satellite

Considerations to keep in mind regarding satellite

Installation can be tricky

Line of sight is required

Satellite

More considerationsLatency can be a problem

Connections are pretty slow

Wireless Networks

As a technician, you must make sure that their computers can connect

Four methods of wireless communication802.11x

Bluetooth

Cellular

Infrared

802.11x

WLAN 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 gAmong all of the wireless technologies covered, 802.11 is the one best suited for WLANs

802.11x Networks

Just like an Ethernet network, only wireless

At 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 Specifications

802.11x networks use the CSMA/CA access method

Similar to that of shared Ethernet

Packet collisions are generally avoided

If they do happen, the sender waits a random period of time (called a back-off time) before transmitting again


802.11Defines WLANs transmitting at 1Mbps or 2Mbps bandwidths using the 2.4GHz frequency spectrumUses FHSS or DSSS for data encoding

802.11a Provides WLAN bandwidth of up to 54Mbps in the 5GHz frequency spectrumUses OFDM, rather than FHSS or DSSSNever gained widespread popularity because 802.11b devices were significantly cheaper and it's highly susceptible to external interference


802.11bProvides for bandwidths of up to 11Mbps in the 2.4GHz frequency spectrumAlso 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


Interoperability concernsNot capable of understanding OFDM transmissionsTo 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


More interoperability concernsWhen operating in mixed mode, 802.11g will use the less-efficient 802.11b back-off timing

Slows down the throughput of the 802.11g access point

The pros of 802.11g/b backward compatibility still far outweigh the cons


802.11nAt the time of this writing, still in development Provides bandwidths from 54Mbps to 600Mbps, but more realistic to expect maximum throughput in the 300Mbps rangeAchieves faster throughput a couple of ways MIMO Channel bonding SDM technologies


802.11n is backward compatible with 802.11a/b/g

802.11n 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


Signal modulation techniques used in the 802.11 standards

Direct-Sequence Spread Spectrum (DSSS)

Frequency-Hopping Spread Spectrum (FHSS)

Orthogonal Frequency Division Multiplexing (OFDM)

802.11x Devices

802.11x Security

The growth of wireless systems has created several opportunities for attackers

Using SSID configurations doesn't necessarily prevent wireless networks from being compromised

WEP

A security standard for wireless devices

Encrypts data to provide data security

Has always been under scrutiny for not being as secure as initially intended

WEP

Vulnerable due to weaknesses in the encryption algorithms

This makes WEP one of the more vulnerable protocols available for security

WPA

An improvement on WEP that was developed in 2003

Implements some of the standards defined in the IEEE 802.11i specification

Improvement over WPA is WPA2, which implements the full 802.11i standard

MAC Filtering

Can be used on a wireless network to prevent certain clients from accessing the network

You 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)

Bluetooth

Makers 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 transmissionsOne of the unusual features of Bluetooth networks is their temporary nature

This dynamically created network is called a piconetA Bluetooth-enabled device can communicate with up to seven other devices in one piconet

Bluetooth Networks

Within the piconet, one device is the master and the other seven devices are slaves

Communication can occur only between the master and a slave

Role of master rotates quickly among the devices in a round-robin fashion

All devices in a piconet can communicate with each other directly

Current 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 Devices

The first device was a wireless headset for a cell phone

Bluetooth-enabled computer peripherals includeKeyboards and mice

Printers

Digital cameras

MP3 players

PDAs and handheld computers

Cars

Bluetooth Devices

Infrared

Longer than light waves but shorter than microwaves

Most 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 communication

Requires line of sight

Infrared

Infrared Networks

A point-to-point network between two devices

No master or slave

No hub-type device required

Point one infrared-enabled device at another and transmit

Infrared Technical Specifications

Current IrDA specifications allow transmission of data up to 16Mbps and IrDA claims that 100Mbps and 500Mbps standards are on the horizonNo concerns of interference or signal conflictsAtmospheric conditions can play a role in disrupting infrared wavesSecurity is not an issue

Data is directional, and you choose when and where to send it

Infrared Devices

Mice

Keyboards

Printers

Keyboards for PDAs

PDAs

Cell phones

Remote control

Cellular (Cellular WAN)

Industry has revolutionized the way we communicate

Primarily been developing in the realm of small handheld communications devices (phones and the BlackBerrys)

Converging technologies -- cell phones and computers

Cellular Networks

Very complex behind the scenes

Cell 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 Specifications

Two major cell standards in the United States: GSM and CDMA

Not compatible with each other

GSM uses a variety of bands to transmitMost popular are 900MHz and 1800MHz

400, 450, and 850MHz are also used

GSM splits up its channels by time division, in a process called Time Division Multiple Access (TDMA)


Maximum 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


CDMA 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 Devices

Further developed in the phone industry than the computer industry

Cell 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 wireless

Not a LAN or a WAN but rather something in between

Makes 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 concentrator

Create 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

networking comptia

Career

network resourcesnetworks

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wans local area networks

lans toinclude networks

network resourcesa resource

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nondedicatedmany networks

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