1 introduction-to-computer-networking
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Transcript of 1 introduction-to-computer-networking
DefinitionDefinition
A computer network is a group of interconnected computers.
It allows computers to communicate with each other and to share resources and information
ComponentsComponents
A minimum of at least 2 computers Cables or wireless communication that
connect the computers to each other. A network interface device on each computer
(this is called a network interface card or NIC) A ‘Switch’ used to switch the data from one
point to another. Network operating system software.
Types of networkTypes of network
The three basic types of networks include:
Local Area Network (LAN)
Metropolitan Area Network (WAN)
Wide Area Network (WAN)
Local Area Network (LAN)
A LAN covers a relatively small area such as a classroom, school, or a single building
LANs are inexpensive to install and also provide higher speeds.
Metropolitan Area Network (MAN)
A MAN spans the distance of a typical metropolitan city
The cost of installation and operation is higher MANs use high-speed connections such as
fiber optics to achieve higher speeds.
Wide Area Network (WAN)
WANs span a larger area than a single city. These use long distance telecommunication
networks for connection, thereby increasing the cost.
The Internet is a good example of a WAN.
Network Configuration
Classification based on how computers behave in a network
Two classifications are: Peer-to-Peer networkPeer-to-Peer network Server based networkServer based network
Peer-to-Peer Networks
In a peer-to-peer network, the networked computers act as equal partners, or peers, to each other.
As peers, each computer can take on the client function or the server function alternately.
Client/Server Networks
In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients.
The server contains the file,
print, application, security, and other services in a central computer that is continuously available to respond to client requests.
Networking hardware
Hub – electronic device (with a number of ports) used in a LAN to link groups of computers
Repeaters (also called amplifiers) – electronic devices that receive signals and amplify and send them along the network
Routers - electronic devices used to ensure messages are sent to their intended destinations
Gateway – consists of hardware and/or software that allows communications between dissimilar networks
Bridge – consists of hardware and/or software that allows communication between two similar networks
Network Topologies
A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.
Bus TopologyBus Topology Also called linear bus One wire connects all
nodes Terminator ends the
wires
Network Topologies
Star TopologyStar Topology All nodes connect to a hub
Packets sent to hubHub sends packet to
destination
Ring TopologyRing Topology Nodes connected in a circle Tokens used to transmit
data
Network Topologies
Mesh TopologyMesh Topology All computers connected
together Internet is a mesh network
Tree TopologyTree Topology Hierarchal Model Combines characteristics of
linear bus and star topologies.
Communications Media
Communications ChannelCommunications Channel
To transfer data from one computer to another requires some type of link through which the data can be transmitted. This link is known as the communications channel.
To send data through the channel requires some type of transmission media, which may be either physical or wireless.
Physical Media
Twisted-pair cable Twisted-pair cable Pair of insulated copper wires Types
Shielded(STP) Unshielded(UTP)
UTP common in LAN Max. cable length – 100 meters Least expensive type of cable Used in many telephone systems
Physical Media
Co-axial cable Co-axial cable Consists of an insulated
center wire grounded by a shield of braided wire
Carries data as electromagnetic signals
Good resistance against interference
Used by the cable television industry
Physical Media
Fiber optic cable Fiber optic cable Core – cylinder of glass Bandwidth is greater, so it
can carry more data Not subject to interference Transfer rate – more than
100 mbps Expensive
Wireless Media
Microwave system Microwave system – transmits data via high-frequency
radio signals through the atmosphereSatellite system Satellite system – receive transmitted signals, amplify
them, and then transmit the signals to the appropriate locations
Wireless Media
Cellular technology Cellular technology – uses antennae resembling telephone
towers to pick up radio signals within a specific area (cell)
Infrared technology Infrared technology – transmits data as infrared light waves
from one device to another, providing wireless links between PCs and peripherals
InternetworkInternetworkAn Internetwork is the connection of two or
more distinct computer networks or network segments via a common routing technology.
Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork.
IntranetAn intranet is a private LAN designed for
use by everyone within an organization. An intranet might consist of an internal e-mail system, a message board and one or more Web site portals that contain company news, forms, and personnel information
ExtranetA network that connects people
within your company with people who are outside your company--all within a secure, password-protected network that can be accessed from anywhere.
InternetA computer network consisting of a
worldwide network of computer networks that use the TCP/IP network protocols to facilitate data transmission and exchange
Internet Connections
Internet backbone : A set of high-speed networks that carry Internet traffic.These networks are provided by companies such as AT&T, GTE, and IBM
Internet service provider (ISP) : A company that provides other companies or individuals with access to the Internet
Internet Connections There are various technologies available that you can
use to connect a home computer to the Internet A phone modem converts computer data into an
analog audio signal for transfer over a telephone line, and then a modem at the destination converts it back again into data
A digital subscriber line (DSL) uses regular copper phone lines to transfer digital data to and from the phone company’s central office
A cable modem uses the same line that your cable TV signals come in on to transfer the data back and forth
Internet Connections
Broadband A connection in which transfer speeds are faster than 128 bits per second DSL connections and cable modems are
broadband connections The speed for downloads (getting data from
the Internet to your home computer) may not be the same as uploads (sending data from your home computer to the Internet)
Packet Switching
To improve the efficiency of transferring information over a shared communication line, messages are divided into fixed-sized, numbered packets
Network devices called routers are used to direct packets between networks
Open System Interconnection (OSI)
The International Organization for Standardization (ISO) established the Open Systems Interconnection (OSI) Reference Model
Each layer deals with a particular aspect of network communication
Network Protocols
Network protocols are layered such that each one relies on the protocols that underlie it
Sometimes referred to as a protocol stack
TCP/IP Protocol
TCP stands for Transmission Control Protocol TCP software breaks messages into packets,
hands them off to the IP software for delivery, and then orders and reassembles the packets at their destination
IP stands for Internet Protocol IP software deals with the routing of packets
through the maze of interconnected networks to their final destination
Internet Connections
Other protocols build on the foundation established by the TCP/IP protocol suite
Simple Mail Transfer Protocol (SMTP)File Transfer Protocol (FTP)TelnetHyper Text Transfer Protocol (HTTP)
Network Security
FIREWALLS :
Network Security
Firewalls can either be hardware and/or software based.
It sits at the gateway between the two networks, usually a private network and a public network such as the internet.
All traffic from inside to outside and vice versa, must pass through the firewall.
Only authorized traffic as defined by the local security policy, will be allowed to pass.
The firewall itself is immune to penetration.