Introduction to Networking Definitions and Terms

Introduction to Networking

Definitions and Terms

Chapter Objectives

After completing this chapter you will:

• Be able to differentiate between peer-to-peer and server-based networks.

• Be able to identify a network topology.

• Understand the different types of network cabling.

• Be able to explain the differences between various network access

methods.

• Understand Ethernet issues.

• Identify OSI model layers.

• Be able to explain when a specific network protocol is used.

• Understand the difference between a MAC address and an IP address.

Chapter Objectives (cont.)


• Be able to correctly apply IP addressing concepts.

• Understand the purpose of DHCP, WINS, and DNS.

• Be able to properly configure a NIC for network connectivity.

• Be able to use common network troubleshooting tools.

• Be able to access a network printer.

• Understand dial-up networking concepts and define commonly used

network terms.



• Be able to define and label the basic parts of a wireless network.

• Know that wireless networks operate at layers 1 and 2 of the OSI model.

• Understand the difference between the two main types of wireless

networks: ad hoc and infrastructure.

• Know the three types of wireless NICs.

• Understand the difference between a BSS and an ESS.

• Be able to explain the purpose of an SSID and channel ID.

• Know the three non-overlapping channel IDs used by the 802.11b

standard.



• Understand the purpose of a wireless repeater.

• Be able to explain the basic differences between the antennas and

explain the concept of attenuation.

• Know the difference between dBd and dBi.

• Know the purpose and importance of a site survey.

• Understand the difference between 802.11a, 802.11b, and 802.11g.

• Understand the basics of wireless network security.

Networking Overview

• A network is two or more devices capable of communicating and sharing

resources between them.

• Two types of networks are LAN and WAN:

– LAN (Local Area Network) – A group of devices sharing resources

in a single area such as a room or a building.

– WAN (Wide Area Network) – Two or more LANs communicating,

often across large distances. The most famous WAN is the Internet.

Types of Local Area Networks

• Two types of LANs are Server-Based and Peer-to-Peer Network:

– Server-Based Network – A basic type of LAN wherein users login to

a controlling computer, called a server and is more secure. The

server contains information about who can connect to the network

and to what shared resources. It also provides some of these

resources. These networks normally consist of 10 or more computers.

– Peer-to-Peer Network – One of two basic types of LANs wherein

each computer user acts as a server. Each computer stores

password and sharing information for its own resources. Usually has

fewer than 10 computers.

• NOS (Network Operating System) – Special operating system on a

server containing utilities for managing users, resources, and security.


Server-Based Network

Network – Figure # 1



Peer-to Peer Network

Network Topologies

• Network Topology – Maps of how the physical or logical paths of network devices connect. The three major topologies are star, ring, and bus.

• Star Topology – Most common Ethernet network topology where each device connects to a central hub or switch.

• Hub – A device used with the Universal Serial Bus or in a star network topology that allows multiple device connections.

• Switch – In star networks, a Layer 2 central controlling device. A switch looks at each data frame as it comes through each port.

• Ring Topology – Network that is physically wired like a star network but, logically in a ring; passes control from one device to the next in a continuous fashion using a special data packet called a token. Used in Token Ring networks.

• Bus Topology – Network wherein all devices connect to a single cable. If the cable fails, the network is down.

• Mesh Topology – Network where all devices connect to each other by cabling to provide link redundancy for maximum fault tolerance. Most likely in WANs.

Network Topologies


Hub/Switch

Network Topologies


Star Topology

Network Topologies

Logical Ring Topology


Network Topologies


Bus Topology

Network Topologies

Network – Table # 1

Network Topologies

Network Cabling

Cable is normally used as a medium for transporting network data. The most

common types are twisted-pair and fiber-optic, although coax is still used in some

old networks.

• Twisted-Pair Cable – Network cable of eight copper wires twisted into four pairs

to prevent crosstalk.

– UTP (Unshielded Twisted-Pair) – Most common network cable that comes

in different categories for different uses. Categories 3 (voice-grade), 4, and 5

(data). It is unshielded and more susceptible to interference.

– STP (Shielded Twisted-Pair) – Same as UTP cable, but with extra foil to

prevent outside noise from interfering with data on the cable.

• Crosstalk – Where signals from one wire interfere with the signal on an adjacent

wire.

• Plenum cable is treated with Teflon or fire retardant materials to reduce the risk of

fire. It produces less smoke and is less toxic when burning.

Network Cabling

• Fiber-Optic Cable – An expensive network cabling made of plastic or

glass fibers that carry data in the form of light pulses. Most often used to

connect network devices such as switches together into a network

backbone or for connecting networks together in a WAN. More secure

and not affected by crosstalk or other interference like copper cable.

– Single-Mode – A type of fiber-optic cabling that sends one light beam

down the cable. Used for longer distance applications.

– Multi-Mode – A type of fiber-optic cabling that allows multiple light

signals to be sent along the same cable. Used for shorter distances.

• Coaxial Cable – Type of copper network cabling used in older Ethernet

networks as well as mainframe and minicomputer connections. Has a

single, center wire conductor with an outer braided shield.

Network Cabling


UTP Cable

Network Cabling


Fiber-Optic Cable

Network Cabling


Coax Cable with Connector

Access Methods

There are standard rules by which computers on a network must adhere

to in order to communicate. These rules are known as a common access

method.

• CSMA/CD (Carrier Sense Multiple Access/Collision Detect) – A

common access method used by Ethernet.

• Token Passing – The common access method used by fiber and Token

Ring networks.

• CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) – A

common access method used in wireless and Apple networks.

• Token – Small data packet passed from one networked device to

another in a ring topology.

Ethernet Issues and Concepts

• Two types of transmissions used in Ethernet networks:

• Half Duplex – A serial device setting that allows either the sending or the

receiving device to send data, one device at a time. Data can travel both

ways on a cable, but not at the same time.

• Full Duplex – A serial device setting that allows the sending and

receiving device to send data simultaneously. Data can travel both ways

on a cable at the same time.

OSI Model

• OSI Model (Open Systems Interconnect) – A standard for information

transfer across a network that was developed by the International

Standards Organization. The model has 7 layers.

– Physical Layer – Layer 1 of the OSI model that defines how bits are

sent and received across the network without regard to their structure.

– Data Link Layer – Layer 2 of the OSI model that accurately transfers

bits across the network by encapsulating (grouping) them into frames.

– Network Layer – Layer 3 of the OSI model that coordinates data

movement between two devices on separate networks.

OSI Model

– Transport Layer – Layer 4 of the OSI model that determines details

on how the data is sent, supervises the validity of the transmission,

and defines protocol for structuring messages.

– Session Layer – Layer 5 of the OSI model that manages

communication and administrative functions between two network

devices.

– Presentation Layer – Layer 6 of the OSI model that defines how data

is formatted, encoded, converted, and presented from the sender to

the receiver, even though different computer language is used.

– Application Layer – Layer 7 of the OSI model that defines how

applications and the computer interact with a network, and negotiates

services such as authentication, error recovery, and quality of service.

OSI Model

• ISP (Internet Service Provider) – A vendor that provides connection to

the Internet.

• Router – A network device that determines the best path to send a

packet. It works at OSI model Layer 3.

OSI Model


OSI Model Layers

OSI Model


OSI Peer Communication

OSI Model

Network – Table # 4

OSI Model

Networking Protocols

• Network Protocol – Specifications that define the network data

communication procedures to follow when sending and receiving data.

– TCP/IP (Transport Control Protocol / Internet Protocol) – the most

common network protocol used by most companies and home users

as a standard protocol. Used to access the Internet.

– IPX/SPX (Internetwork Packet Exchange/Sequenced Packet

Exchange) – original protocol used for connecting to Novell networks.

Now TCP/IP is the standard protocol used.

– NetBEUI (NetBIOS Enhanced User Interface) – is a non-routable

protocol used in simple networks; commonly found on peer-to-peer

networks.

Network Addressing

Network devices have to be able to identify each other in order to

communicate across a network. They do this through various network

addressing schemes.

• MAC Address – One of two types of addresses assigned to network

adapters, used when two devices on same network communicate.

• IP Address – A type of network adapter address used when multiple

networks are linked. It is a 32-bit binary number with groups of eight bits

separated by a dot.

• Network Number – Portion of an IP address that represents which

network the computer is on.

Network Addressing

• Host Number – Portion of an IP address that represents the specific

network device.

• Broadcast Address – IP address used to communicate with all devices

on a particular network.

• Subnet Mask – A number the computer uses to determine which part of

an IP address represents the network and which portion represents the

host.

Network Addressing


IP Addressing (Network Number and Host Number)

Network Addressing


IP Addressing (Two Network Example)

Network Addressing

Network – Table #5

IP Address Information

Configuring Networking

Some key terms to understand when configuring computers for networking are:

• UNC (Universal Naming Convention) – A standard way of naming computers

and shared resources on a network. Used at the command prompt to obtain

network shares.

• DHCP (Dynamic Host Configuration Protocol) – A method to automatically

assign IP addresses to network devices from a pool of IP addresses. A computer

requests an address from another device running DHCP, usually a server,

receives it, and joins the network.

• APIPA (Automatic Private IP Addressing) – Assigns an IP address and mask to

the computer when a DHCP server is not available.

• Default Gateway – The IP address of the Layer 3 device, such as a router, that

is directly connected to its immediate network and acts as a doorway or director

to other remote networks.


• DNS (Domain Name System) Server – Application on a network server

that translates Internet names (also known as Fully Qualified Domain

Names or hostnames) into IP addresses.

• URL (Universal Resource Locator) – A method of accessing Internet

resources by using a simple, easily remembered name assigned to an IP

address. An example of a URL is: www.scottjonespub.com, which is

much easier to remember than the IP address : 167.160.239.173.

• WINS (Windows Internet Naming Service) Server – Keeps track of IP

addresses assigned to a specific computer name. A user can type in a

computer name to connect and the server will translate it to the

computer’s IP address.


Network – Figure #17

Default Gateway

Network Troubleshooting

IPCONFIG – A command used with Windows 98, NT, and 2000 to see

and modify the current IP settings.

• NSLOOKUP – An NT Server and 2000 Server troubleshooting tool that

displays network domain names and their associated IP addresses.

• Tracert – A network troubleshooting command that displays the path a

data packet takes through a network, thus allowing one to see where a

fault occurs in larger networks.



Sample Network Configuration



WINIPCFG



IPCONFIG

Dial-up Networking

There are several ways in which computers can connect to remote

networks:

• DUN (Dial-Up Networking) – A remote computer that dials into the

Internet or a corporation using a modem.

• VPN (Virtual Private Networking) – A remote computer connecting to a

remote network by “tunneling” over an intermediate network, such as the

Internet or a LAN.

• PPP (Point-to-Point Protocol) – A connection-oriented Layer 2 protocol

that encapsulates data for transmission over remote networks. Very

common for home users dialing in to the Internet.

Dial-up Networking

Dial-Up Networking and VPN


Dial-up Networking

Network Connections

Network - Table #7

Internet Software

Once a connection is established to a remote network there are several

program types that are useful for accessing data.

• Browser – A program that views web pages across the Internet. The two

most common are Internet Explorer and Netscape Navigator.

• Proxy Server – Acts as an agent between an application and a real

server for security purposes.

• SMTP (Simple Mail Transport Protocol) – is a protocol used for

sending and receiving email. Settings for configuring email can be

obtained from the network administrator or the ISP being used to connect

to the Internet.

Internet Security

• There are three major points to remember:

– Keep service patches updated on a regular basis.

– The latest anti-virus software should be installed and constantly

updated.

– If the computer connects to the internet, it should be connected

behind a firewall.

• Cookie – A special program written to collect information and store it on

the hard drive. This will contain your preferences when you visit a

website.

• Firewall – Software or hardware that protects one or more computers

from outside attacks.

Network Terminology

• Networking Terms and Acronyms To be Familiar With:

– Backbone Bandwidth Baseband

– Broadband E-mail Fast Ethernet

– FDDI Frame FTP

– HTML HTTP Infrared

– Packet POP SNMP

– TCP Telnet UDP

Wireless Networks Overview

• Wireless Networks – Transmit data over air using either infrared or radio

frequencies. Wireless networks operate at layers 1 and 2 of the OSI

model.

Wireless Networks Types

• There are two main types of wireless networks:

– Ad hoc – also known as peer-to-peer or IBSS (Independent Basic

Service Set) – An ad hoc wireless network is when at least two

devices such as two computers have wireless NICs.

– Infrastructure – Wireless network that connects multiple wireless

network devices through an Access Point.

• Access Point – is similar to a network hub and connects wireless network

devices.

• There are three major types of wireless NICs: PC Card, USB, and PCI.


• BSS (Basic Service Set) – Configuration when multiple devices connect

to an Access Point.

• ESS (Extended Service Set) – The network design when multiple Access

Points connect to the same main network.

• SSID (Service Set Identifier) - A set of 32 alpha numeric characters used

to differentiate between wireless networks.

• The channel ID (frequency) between the Access Point and the adapter

must match for communication to occur.


802.11b Frequency Channels

Network – Table #12

Wireless Network Security Overview

• Wireless networks by their nature are insecure.

• All transmissions over air occur in clear text making them easy to

compromise.

Authentication and WEP

• Authentication is the process of determining that a network device or

person has permission to enter the wireless network through the access

point.

• Open Authentication – Allows a wireless network device to send a frame

to the access point with the sender’s identity (MAC address). It is used

when no authentication is required.

• Shared Key Authentication – Requires the use of a shared key to

communicate.

• WEP (Wireless Equivalent Privacy) – Encrypts data when shared key

authentication is used.

• Encryption – the process of converting data into an unreadable format.

Default Settings

• All wireless networks have default passwords and SSIDs. They should

be changed immediately to prevent hackers from gaining access.

• SSID Broadcasting – The access point periodically sends out a beacon

frame that includes the SSID.

Default Access Point Passwords

Introduction to Networking Definitions and Terms

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Introduction to Networking Definitions and Terms