Transcript Network - UT Computer Science

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.)
After completing this chapter you will:
• 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.
Chapter Objectives (cont.)
After completing this chapter you will:
• 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.
Chapter Objectives (cont.)
After completing this chapter you will:
• 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.
Types of Local Area Networks
Server-Based Network
Network – Figure # 1
Types of Local Area Networks
Peer-to Peer Network
Network – Figure # 2
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 – Figure # 3
Network Topologies
Star Topology
Network – Figure # 4
Network Topologies
Logical Ring Topology
Network – Figure # 5
Network Topologies
Bus Topology
Network – Figure # 6
Network Topologies
Network Topologies
Network – Table # 1
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 – Figure # 7
Network Cabling
Fiber-Optic Cable
Network – Figure # 11
Network Cabling
Coax Cable with Connector
Network – Figure # 12
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
Network – Figure # 13
OSI Model
OSI Peer Communication
Network – Figure # 14
OSI Model
OSI Model
Network – Table # 4
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 – Figure # 15
Network Addressing
IP Addressing (Two Network Example)
Network – Figure # 16
Network Addressing
IP Address Information
Network – Table #5
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.
Configuring Networking
• 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.
Configuring Networking
Default Gateway
Network – Figure #17
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.
Network Troubleshooting
Sample Network Configuration
Network – Figure #18
Network Troubleshooting
WINIPCFG
Network – Figure #19
Network Troubleshooting
IPCONFIG
Network – Figure #20
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
Network – Figure #21
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.
Wireless Networks Types
• 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.
Wireless Networks Types
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