Networking Comptia
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Transcript of 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
Networking Fundamentals
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 Fundamentals
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
Networking Fundamentals
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)
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Because of the speed increases, categorizing networks based on connection speed is outdated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
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
Peer-to-Peer Networks
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
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
Client-Server Resource Model
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
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 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
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 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
IEEE 802.5 Token Ring
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
IEEE 802.5 Token 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
TCP/IP
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
Parts of the IP Address
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
Parts of the IP Address
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
Sending and Controlling Data
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
Sending and Controlling Data
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
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
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
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
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
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
802.11x Technical Specifications
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
802.11x Technical Specifications
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
802.11x Technical Specifications
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
802.11x Technical Specifications
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
802.11x Technical Specifications
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
802.11x Technical Specifications
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
802.11x Technical Specifications
802.11x Technical Specifications
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
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)
Cellular Technical Specifications
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
Cellular Technical Specifications
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