Chapter 12: Behind the Scenes: networking and security in the business world
A network is a group of two or more computers (or nodes) that are configured to
share information and resources such as printers, files, and databases
- Enables computers and other devices to communicate with each other
What advantages do businesses gain from networks?
- Increase productivity through information sharing
- Enable expensive resources to be shared such as peripherals
- Facilitate knowledge sharing through databases
- Enables software sharing accessible from the server
- Facilitates Internet connectivity which decreases cost
- Enables enhanced communication through social networking tools
Are there disadvantages to using networks?
Network administrators have training in computer and peripheral maintenance
and repair, networking design, and installation of networking software
Networks require special equipment and software
A server is a computer that stores and shares resources on a network
A client is a computer that requests resources from a server
A client/server network contains servers as well as client computers
Does my home network have a server?
Home P2P networks do not need servers
Computers act as both clients and servers when appropriate
When shouldn’t a peer-to-peer network be used?
Become difficult to administer when expanded to more than 10 users
Client/server networks move data more efficiently than P2P networks
Besides having a centralized server, what makes a client/server network different
from a peer-to-peer network?
Main difference is scalability
Scalability means that more users can be added easily without affecting the
performance of the other network nodes (computers and peripherals)
Also, peer-to-peer networks are decentralized
Decentralized means that users are responsible for creating their own data dack-
ups and for providing security for their computers
Client/server networks are centralized
Centralized means that all clients connect to a server that performs tasks for them Classifications of Client/Server Networks: LANs, WANs, and MANs
Four popular classifications
1. Local area networks (LAN): is a group of computers and peripherals linked
together over a relatively small geographical area
2. Wide area networks (WAN): comprises large numbers of users over a
wider physical area or separate LANs that are mils apart
3. Metropolitan area networks (MAN): established WANs that link users in a
specific geographical area
4. Personal area networks (PAN) a network used to connect wireless devices
that are in close proximity to each other
EX Bluetooth-enabled devices
o Bluetooth technology uses radio waves to transmit data over short
- Are wireless and work within the personal operating system of an individual
o Within 30 feet of one’s body
What other sorts of networks do businesses use?
An intranet is a private network set up by an entity that is used exclusively by a
select group of individuals
- Facilitates information sharing, database access, group scheduling,
- Deployed via Transmission Control Protocol/Internet Protocol (TCP/IP)
- Not accessible by unauthorized individuals
- First main use was to run groupware
Extranet is an area of intranet that only certain corporations or individuals can
- Useful for enabling electronic data interchange (EID)
o Allows the exchange of large amounts of business data in a
standardized electronic format
What security tools do intranets and extranets use?
Virtual private networks (VPN) uses public Internet communications
infrastructure to build a secure, private network among various locations
- Use special security technologies and protocols that enhance security,
enabling data to traverse the Internet as securely as if it were on a private
Tunneling is the main technology for achieving a VPN
- Data packets are placed inside other data packets
Tunnel interface is the format of these external data packets is encrypted and is
understood only by the sending and receiving hardware
Constructing Client/Server Networks
Server: client/server networks contain at least one computer that functions solely
as a server Network topology: the layout and structure of the network
Transmission media: cable or wireless communications technology between
clients and servers in a network
Network operating system (NOS) software: required in all client/server
networks, enables the network to function
Network adapter: all nodes on the network require adapters that enable the
computer to communicate with the network using a common data communication
language or protocol
Network navigation device: specialized network navigation devices are needed to
move data signals around the network (routers, switches, bridges)
What types of servers are found on larger client/server networks?
A dedicated server is a server used to fulfill one specific function
EX. Handling e-mail
What are authentication and file servers?
An authentication server is a server that keeps track of who is logging on to the
network and which services on the network are available to each user
A file server is a server that stores and manages files for network users
What functions do dedicated servers handle?
Repetitive or time-consuming tasks for the CPU are good candidates to regulate to a
- Print servers, application servers, database servers, e-mail servers,
communication servers, Web servers
How does a print server function?
Print servers manage all client-requested printing jobs for all printers on a
How does the printer know which documents to print?
A print queue is a software holding area for print jobs
- When the print server receives a job from a client computer, it puts the job
into a print queue on the print server
Application Servers: What function does an application server perform?
An application server acts as a repository for application software
- When a client computer connects to the network and requests an application,
the application server delivers the software to the client computer
Database Servers: what does a database server do?
A database server provides client computers with access to information stored in
databases E-Mail Servers: how is e-mail handled on a large client/server network?
Function of an e-mail server is to process and deliver incoming and outgoing e-mail
Communications Servers: what types of communications does a communications
A communications server handles all communications between the network and
other networks, including managing Internet connectivity
All requests for information from the Internet and all messages being sent through
the Internet pass through the communications server
Often is the only server connected to the Internet
Web Servers: what function does a Web server perform?
A Web server is used to host a Web site so it will be available through the Internet
Networks have different blueprints denoting their layout
Network topology refers to the physical or logical arrangement of computers,
transmission media (cable), and other network components
Physical topology refers to the layout or the “real” components of the network
Logical topology refers to the virtual connections among network nodes
What does a bus topology look like?
In a bus (or linear bus) topology, all computers are connected in sequence on a
- Often deployed in peer-to-peer networks
- Each computer on the network can communicate directly with each other
Data collisions happen when two computers send data at the same time and they
collide somewhere in the media
- Often lost or irreparably damaged
- Happen often because there is only one main communication medium
An access method has to be established to control which computer is allowed to
use the transmission media at a certain time
How does data get from point to point on a bus network?
Data is broken into small segments called packets
- Contains address of computer or peripheral device to which it is being sent
A bus network is a passive topology because devices attached to it to nothing to
move data along the network
A terminator is a device that absorbs a signal so that it is not reflected back onto
parts of the network that have already received it
What are the advantages and disadvantages of bus networks?
Advantage: they are simple and low cost Disadvantage: if there is a break in the cable the network is disrupted because some
of the computers are cut off from the network
What does a ring topology look like?
Computer and peripherals in a ring (or loop) topology are laid out in a
configuration resembling a circle
Data flows in one direction only
Data is passed using a data packet called a token
How does a token move data around a ring?
A token is passed from computer to computer around the ring until it is grabbed by
a computer that needs to transmit data
- Only one computer in the ring can “hold” the token at a time
The token method is when the sending node generates a new token
Ring topology is an active topology meaning that nodes participate in moving data
through the network
Is a ring topology better than a bus topology?
Advantage: ring topology performance will remain acceptable even with large
numbers of users
Disadvantage: if one computer fails, it can bring the entire network to a halt because
that computer is unavailable to retransmit tokens and data
What is the layout for a star topology?
A star topology is the most widely deployed client/server network layout because
it offers the most flexibility for a low price
- Nodes connect to a central communication device called a switch in a pattern
resembling a star
Is an active topology because the switch retransmits data signals
If the switch fails the network no longer functions
Many use Ethernet protocol (a communications protocol)
A protocol is a set of rules for exchanging communication
How do computers on a star network avoid data collisions?
CSMA/CS (carrier sense multiple access with collision detection); a node
connected to the network uses carrier sense to verify that no other nodes are
currently transmitting data signals
What happens when the signals collide?
A jam signal alerts other computers on the network that there is a collision
What are the advantages and disadvantages of a star topology