Unit 07 - LO1

Computer Network Systems
LO1 - Know types of network systems and protocols
P1 - Describe the types of networks available and how they relate to particular
network standards and protocols
M1 - Compare and contrast different network standards and protocols [IE3]
P2 - Describe why different network standards and protocols are necessary
P3 - Explain the key components required for client workstations to connect to a
network and access network resources
M2 - Compare the different options for the key components for an identified
user’s needs [IE1, CT1]
D1 - Develop proposals for networked solutions to meet an identified user’s need
P4 - Explain the function of interconnection devices
P5 - Describe typical services provided by networks
M3 - Describe where different network services would be used.
P6 - Make a networked system secure.
D2 - Evaluate the procedures organisations should take to secure their networks
P1 - Describe the types of networks available and how they relate to particular network
standards and protocols
M1 compare the benefits and disadvantages of peer-to-peer network and client/server
networks [IE3]
P2 describe why different network standards and protocols are necessary
The suggested scenario is that learners have been employed to explain possible network
solutions to a business client
 For P1, describing networks, protocols and standards, learners could produce a
report/poster using diagrams. Alternatives are a small set of linked web pages or a
 For P2, learners should be able to demonstrate they understand why different
network standards and protocols are necessary. Examples given should be realistic.
This can be linked to P1.
 Before attempting M1, learners should, ideally, have the chance to see the operation
of both types of networks and then the actual evidence presented as a verbal,
written report etc would be based on real experience.
You have been employed to explain possible network solutions to the management of a new
primary school in the local area with a view to setting up, installing and protecting their
networked machines and the information stored on these.
The client at the end of the month wants a working network with expansion capabilities
allowing up to 200 computers in different computer suites across the building to be connected,
the addition of printers and shared resources, a central network pool for information and the
capability of adding their media suite of Apples to this network on a restricted access basis.
Currently they have two sites, the upper primary and lower primary that are not connected
physically. They have100 workstations in the student areas across both sites, 50 base unit
computers in the administration and staffing areas, 25 laptops in separate laptop cabinets and
25 Apple G4’s in the media suites. They have 20 shared printers across the two buildings, ten of
which are accessible to students with network capabilities including one networkable colour
printer in their library in the upper primary building.
The school has been given several possible scenarios by their newly assigned network manager
needs to know what would be best for the school, the future and how to protect this network
from the outside and inside. Longer term they expect to have a working intranet accessible off
site where files can be accessed on the network drives by students.
There are three main types of networks that companies use:
 local area network (LAN);
 wide area network (WAN), internet; WAN technologies
e.g. frame relay, MPLS, ATM;
 Personal Area Network (PAN)
Each of these Network systems has their own uses within a
business environment and each have their own merits for
the client/user. The choice of these is dependent on the size
of the company, the need for security, the physical layout
and proposed intent of the user. Even with forty years of
network developments, the need for these layouts and
protocols has not changed.
LAN – Local Area Network
Networked computers
linked by cables.
Networks were developed
allowing standalone
computers to communicate
with each other through
Processing is carried out both
centrally on a ‘server’ and on the
computers. These computers can
either be base Units(machines with
storage) or workstations (thin client).
LANs allow local network
access allow global
network access (such as to
the Internet) by linking
back to a network server.
Different types of
cabling allows
between computers
e.g. Star, linear, ring.
Local Area Network
A Local Area Network (LAN) is a network that is confined to a relatively small area. It is
generally limited to a geographic area such as a writing lab, school, or building. Rarely
are LAN computers more than a mile apart.
In a typical LAN configuration, one computer is designated as the file server. It stores all
of the software that controls the network, as well as the software that can be shared by
the computers attached to the network. Computers connected to the file server are
called workstations.
The workstations can be less powerful than the file server, and they may have additional
software on their hard drives. On many LANs, cables are used to connect the network
interface cards in each computer; other LANs may be wireless.
All non wireless devices are connected along the cabling and information flows along
that line through direct or an indirect path if the path is blocked or busy like water would
flow through inter-connected pipes. Directing this traffic are hubs, routers and servers.
WAN Network
File Server
LAN Technologies - Ethernet, Appletalk, Token Ring, Arcnet
OS Microsoft
Wide Area Network
Wide Area Networks (WANs) connect larger geographic areas, such as
Florida, the United States, or the world. Dedicated transoceanic cabling or
satellite uplinks may be used to connect this type of network.
Using a WAN, schools in Florida can communicate with places like Tokyo in a
matter of minutes, without paying enormous phone bills. These are usually
dedicated or protected lines that separate the system from the Internet
A WAN is complicated. It uses multiplexers to connect local and
metropolitan networks to global communications networks like the
Internet. To users, however, a WAN will not appear to be much different
than a LAN except for geographical location and speed of use.
P1.1 - Types of Network
PAN Network - is a computer network organized around an individual person. Personal
area networks typically involve a mobile computer, a cell phone and/or a handheld
computing device such as a PDA. You can use these networks to transfer files including
email and calendar appointments, digital photos and music.
Personal area networks can be constructed with cables or wirelessly. USB and FireWire
technologies often link together a wired PAN while wireless PANs typically use Bluetooth
or sometimes infrared connections. Bluetooth PANs are also called piconets.
Personal area networks generally cover a range of less than 10 meters (about 30 feet).
Unlike with wireless LANs, only devices within this limited area typically participate in the
network, and no online connection with external devices is defined.
One device is selected to assume the role of the controller during wireless PAN
initialization, and this controller device mediates communication within the WPAN. The
controller broadcasts a beacon that lets all devices synchronize with each other and
allocates time slots for the devices.
P1.1 – PAN Network
Each device attempts
to join the wireless
PAN by requesting a
time slot from the
controller. The
authenticates the
devices and assigns
time slots for each
device to transmit
data. The data may be
sent to the entire
wireless PAN using the
wireless PAN
destination address, or
it may be directed to a
particular device.
P1.1 - Types of Network
P1.1 - Task 01 – Describe the technical purposes of Workstations,
Base Units and associated peripherals.
P1.1 – Task 02 – Describe different common types of networks,
and in technical detail describe how information is transferred
around the system in terms of information flow.
For your client, they will need to connect all the machines in
both buildings with a secure network layout with a system that
links and shares files. They will need to share resources across
these systems but have a separation between servers for
different levels of students.
P1.1 – Task 03 – Suggest a Network system type and workstation
purchase that will suit the needs of your client.
P1.2 – WAN information transference
Transferring information within a WAN network is done
through systems of small bites send in sequence so the
computer receiving the information can understand and
have time to decipher the information as it is being sent.
This is called Packet Switching. WAN particularly deals with
these packets in a number of ways depending on how the
network manager has constructed the network layers and
protocols. One system is necessary, everything else will
evolve around that packet switching method when that
decision is made. Deciding in which type of WAN to
construct can
P1.2 – WAN information transference
MPLS is a type of switching, MPLS (multiprotocol label switching), was introduced by
the IETF in 1999. As its name implies, MPLS enables multiple types of layer 3
protocols to travel over any one of several connection-oriented layer 2 protocols. IP
addressing is the most commonly used layer 3 protocol, and so MPLS most often
supports IP. MPLS can operate over Ethernet frames, but is more often used with
other layer 2 protocols, like those designed for WANs. In fact, one of its benefits is
the ability to use packet-switched technologies over traditionally circuit switched
networks. MPLS can also create end-to-end paths that act like circuit-switched
ATM - (Asynchronous Transfer Mode) functions in the Data Link layer. Its ITU
standard prescribes both network access and signal multiplexing techniques.
Asynchronous refers to a communications method in which nodes do not have to
conform to any predetermined schemes that specify the timing of data
transmissions. In ATM communications, a node can transmit at any instant, and the
destination node must accept the transmission as it comes. To ensure that the
receiving node knows when it has received a complete frame, ATM provide start
and stop bits for each character transmitted. When the receiving node recognizes a
start bit, it begins to accept a new character. When it receives the stop bit for that
character, it ceases to look for the end of that character’s transmission. ATM data
transmission, therefore, occurs in random stops and starts.
P1.2 – WAN information transference
X.25 is an analog, packet-switched technology designed for longdistance data transmission and standardized by the ITU. The original
standard for X.25 specified a maximum of 64-Kbps throughput, but
by 1992 the standard was updated to include maximum throughput
of 2.048 Mbps. It was originally developed as a more reliable
alternative to the voice telephone system for connecting mainframe
computers and remote terminals. Later it was adopted as a method of
connecting clients and servers over WANs.
Frame relay is an updated, a digital version of X.25 that also relies on
packet switching. ITU and ANSI standardised frame relay in 1984.
Frame relay protocols operate at the Data Link layer of the OSI model
and can support multiple different Network and Transport layer
protocols. The name is derived from the fact that data is separated
into frames rather than packets, which are then relayed from one
node to another without any verification or processing.
P1.1 – Task 04 – Describe with examples WAN information transfer technologies.
X.25 and Frame Relay
A topology is the shape or configuration of
the network i.e. the way nodes are
connected. The different types of topology
depends on the geographic, physical and
capable layouts of the space it is installed and
each has their own benefits.
Topologies are considered logical or physical
topologies e.g. star, bus, ring, mesh, tree.
A start topology is a network set out in the
shape of a star, branching from one central fibre
to the outliers.
A star topology is designed with each node (file
server, workstations, and peripherals) connected
directly to a central network hub, switch, or
Data on a star network passes through the hub,
switch, or concentrator before continuing to its
destination. The hub, switch, or concentrator
manages and controls all functions of the
network. It also acts as a repeater for the data
flow. This configuration is common with twisted
pair cable; however, it can also be used with
coaxial cable or fiber optic cable.
Advantages of a Star Topology
Easy to install and wire.
No disruptions to the network when connecting or removing
Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
Requires more cable length than a linear topology.
If the hub, switch, or concentrator fails, nodes attached are
More expensive than linear bus topologies because of the cost
of the hubs, etc.
A linear bus topology consists of a main run of cable
with a terminator at each end. All nodes (file server,
workstations, and peripherals) are connected to the
linear cable.
Using T junctions, more machines and peripherals
can be added to the main line of cable. Information is
sent down the cable to the router if the cable is long,
or the server is the system is short where the
information is dealt with.
This relies heavily on the speed and function of the
main trunk line.
Similar to a real bus, information can step off along
the line when it reaches its destination or can
continue to the server (main depot) where it then
gets sent back down the line to its destination like a
print job coming out of a printer.
Advantages of a Linear Bus Topology
 Easy to connect a computer or peripheral to a linear bus.
 Requires less cable length than a star topology.
Disadvantages of a Linear Bus Topology
 Entire network shuts down if there is a break in the main
 Terminators are required at both ends of the backbone
 Difficult to identify the problem if the entire network
shuts down.
 Not meant to be used as a stand-alone solution in a
large building.
Mesh Network is a network where all the nodes are connected to each
other and is a complete network. In a Mesh Network every node is
connected to other nodes on the network through hops. Some are
connected through single hops and some may be connected with more
than one hope.
While the data is travelling on the Mesh Network it is automatically
configured to reach the destination by taking the shortest route which
means the least number of hops. Data travels by hopping from one
node to another and then reaches the destination node in a Mesh
Topology Network.
The advantage of a mesh topology is that if one cable breaks, the
network can use an alternative route to deliver its packets.
Mesh networks are not very practical in a LAN setting. For example, to
network eight computers in a mesh topology, each computer would
have to have seven network interface cards, and 28 cables would be
required to connect each computer to the seven other computers in
the network. Obviously, this scheme isn’t very scalable.
However, mesh networks are common for metropolitan or wide area
networks. These networks use devices called routers to route packets
from network to network. For reliability and performance reasons,
routers are usually arranged in a way that provides multiple paths
between any two nodes on the network in a mesh-like arrangement.
The Mesh Network is based on a very
sensible concept and has lesser chances of a
network breakdown. There are so many
possible combinations of routes and hops a
data transfer can take that it will reach the
destination one way or the other. It is highly
unlikely that all the nodes in a single Mesh
Network will break down at any given point
of time
A tree topology combines characteristics of
linear bus and star topologies. It consists of
groups of star-configured workstations
connected to a linear bus backbone cable.
Tree topologies allow for the expansion of an
existing network, and enable companies to
configure a network to meet their needs.
Tree networks are usually made out of
necessity, more machines in one room,
printers in another etc and a combination of
different technologies usually exist until
something better comes along.
Advantages of a Tree Topology
Point-to-point wiring for individual segments.
Supported by several hardware and software companies.
Disadvantages of a Tree Topology
Overall length of each segment is limited by the type of
cabling used.
If the backbone line breaks, the entire segment goes down.
More difficult to configure and wire than other topologies.
A Ring Topology network is a localised network
joined by a central line that forms a loop.
Information can find its way around the loop in
either direction as long as there is an unbroken
Computers can be joined to the loop through T
junctions of drop cables as can additional
This makes everything localised and is usually
formed on a single room or bank of computers.
The smaller the ring, the quicker information can
pass to the relevant point. This also allows
computers to act as individual servers like an
email server or print server.
Advantages of a Ring Network
Information can flow both ways around the
ring in order to reach its goal. One of the easier
networks to set up and easy to add additional
devices to. System is localised so there is less
Disadvantages of a Ring Network
Loop needs to be completed or terminated at
one end. A break in the cable brings the whole
thing down. File server needs to be localised or
the ring joined to the trunk line.
P1.2 – Task 05 – Define and describe how Network topologies work and how they
transfer information from station to station.
M1.2 – Task 06 – Suggest a Network Topology for your Client and Define and describe
the benefits and disadvantages of using this topology in a school environment.
A protocol is a set of rules that enables effective communications to occur. We encounter protocols every day.
For example, when you pay for groceries with a check, the clerk first tells you how much the groceries cost.
You then write a check, providing information such as the date, the name of the grocery store, the amount
written with numerals and spelled out, and your signature, and you give the check to the clerk. The clerk
accepts the check and asks to
see your driver’s license. You show the clerk your driver’s license, and the clerk looks at it, looks at you, looks
at your driver’s license again, writes the driver’s license number on the check, asks whether you’ve gained
some weight since the picture was taken, and then accepts the check.
Here’s another example of an everyday protocol: making a phone call. You probably take most of the details
of the phone calling protocol for granted, but it’s pretty complicated if you think about it:
When you pick up a phone, you have to listen for a dial tone before dialling the number. If you don’t
hear a dial tone, you know that either (1) someone else in your family When you hear the dial tone,
you initiate the call by dialling the number of the party you want to reach. If the person you want to
call is in the same area code as you, most of the time you simply dial that person’s seven digit
phone number. If the person is in a different area code, you dial a one, the five-digit dialling code,
and the person’s six-digit phone number.
If you hear a series of long ringing tones, you wait until the other person answers the phone. If the
phone rings a certain number of times with no answer, you hang up and try again later. If you hear a
voice say, “Hello,” you can begin a conversation with the other party. If the person on the other end
of the phone has never heard of you, you say, “Sorry, wrong number,” hang up, and try again.
If you hear a voice that rambles on about how they’re not home but they want to return your call,
you wait for a beep and leave a message. Etc. Etc.
In computer terms network access and protocols work along the same line.
The OSI model breaks the various aspects of a computer network into seven distinct layers. These layers are kind of
like the layers of an onion: Each successive layer envelops the layer beneath it, hiding its details from the levels
above. The OSI model is also like an onion in that if you start to peel it apart to have a look inside, you’re bound to
shed a few tears.
The OSI model is not a networking standard in the same sense that Ethernet and Token Ring are networking
standards. Rather, the OSI model is a framework into which the various networking standards can fit. The OSI model
specifies what aspects of a network’s operation can be addressed by various network standards. So, in a sense, the
OSI model is sort of a standard of standards.
The first three layers are sometimes
called the lower layers. They deal with
the mechanics of how information is
sent from one computer to another
over a network. Layers 4 through 7 are
sometimes called the upper layers.
They deal with how applications
programs relate to the network through
application programming interfaces.
The Seven layers
The bottom layer of the OSI model is the Physical layer and addresses the physical characteristics of the
network, such as the types of cables used to connect devices, the types of connectors used, how long the cables
can be, etc. For example, the Ethernet standard for 10BaseT cable specifies the electrical characteristics of the
twisted-pair cables, the size and shape of the connectors, the maximum length of the cables, and so on. The
star, bus, ring, and mesh network topologies in Task P1.1 apply to the Physical layer.
The Data Link layer is the lowest layer at which meaning is assigned to the bits that are transmitted over the
network. Data link protocols address things such as the size of each packet of data to be sent, a means of
addressing each packet so that it’s delivered to the intended recipient, and a way to ensure that two or more
nodes don’t try to transmit data on the network at the same time. The Data Link layer also provides basic error
detection and correction.
The Network layer handles the task of routing network messages from one computer to another. The two most
popular layer 3 protocols are IP (which is usually paired with TCP) and IPX (normally paired with SPX for use with
Novell and Windows networks).
The Transport layer is the layer where you’ll find two of the most well-known networking protocols: TCP
(normally paired with IP) and SPX (normally paired with IPX). As its name implies, the Transport layer is
concerned with the transportation of information from one computer to another. The main purpose of the
Transport layer is to ensure that packets are transported reliably and without errors. The Transport layer does
this task by establishing connections between network devices, acknowledging the receipt of packets, and
resending packets that are not received or are corrupted when they arrive.
The Seven layers
The Session layer establishes conversations known as sessions between networked devices. Each of these
transmissions is handled by the Transport layer protocol. The session itself is managed by the Session layer
protocol. A single session can include many exchanges of data between the two computers involved in the
session. After a session between two computers has been established, it is maintained until the computers agree
to terminate the session.
The Presentation layer is responsible for how data is represented to applications. Most computers including
Windows, UNIX, and Macintosh computers use the American Standard Code for Information Interchange (ASCII) to
represent data. However, some computers (such as IBM mainframes) use a different code, which is not compatible
with each other. To exchange information between a mainframe computer and a Windows computer, the
Presentation layer must convert the data from ASCII to the other language and vice versa. The Presentation layer
can also apply compression techniques so that fewer bytes of data are required to represent the information
when it’s sent over the network. At the other end of the transmission, the Presentation layer then uncompresses
this data.
The Application layer, deals with the techniques that application programs use to communicate with the network.
Application programs such as Microsoft Office aren’t a part of the Application layer. Rather, the Application layer
represents the programming interfaces that application programs such as Microsoft Office or Adobe products use
to request network services. Some of the better-known Application layer protocols are DNS (Domain Name
System) for resolving Internet domain names. FTP (File Transfer Protocol) for file transfers. SMTP (Simple Mail
Transfer Protocol) for e-mail etc.
Token passing
In CSMA/CD and CSMA/CA the chances of collisions are there.
As the number of hosts in the network increases, the chances
of collisions also will become more. In token passing, when a
host want to transmit data, it should hold the token, which is
an empty packet. The token is circling the network in a very
high speed. If any workstation wants to send data, it should
wait for the token. When the token has reached the workstation,
the workstation can take the token from the network, fill it with
data, mark the token as being used and place the token back to
the network.
This benefits a network because it means information is shared and queued, when one machine is ready
and ahs been waiting it will get the basket and pass on the information in a first come, first serve basis. This
can be seen like a printer waiting t print you network job when others are ahead of you. Your network takes
the next token and when it is your turn it then gets its place in the queue while you get on with the other
jobs that need doing.
P1.3 – Task 07 – Describe the system of CSMA and Token Passing
M1.3 – Task 08 – Explain Token Passing and CSMA in terms of how this system would benefit
students within a school environment.
The TCP/IP family uses four layers while ISO OSI
uses seven layers as shown in the figure above.
The TCP/IP and ISO OSI systems differ from each
other significantly, although they are very similar
on the network and transport layers.
Except for some exceptions like SLIP or PPP, the
TCP/IP family does not deal with the link and
physical layers. Therefore, even on the Internet,
we use the link and physical protocols of the ISO
OSI model.
TCP/IP (Transmission Control Protocol/Internet
Protocol) is the basic communication language
or protocol of the Internet. It can also be used as
a communications protocol in a private network
(either an intranet or an extranet). When you
are set up with direct access to the Internet,
your computer is provided with a copy of the
TCP/IP program just as every other computer
that you may send messages to or get
information from also has a copy of TCP/IP.
TCP/IP is a two-layer program. The higher layer, Transmission Control Protocol, manages the
assembling of a message or file into smaller packets that are transmitted over the Internet and
received by a TCP layer that reassembles the packets into the original message. The lower layer,
Internet Protocol, handles the address part of each packet so that it gets to the right destination.
Each gateway computer on the network checks this address to see where to forward the message.
Even though some packets from the same message are routed differently than others, they'll be
reassembled at the destination.
TCP/IP uses the client/server model of communication in which a computer user (a client)
requests and is provided a service (such as sending a Web page) by another computer (a server) in
the network. TCP/IP communication is primarily point-to-point, meaning each communication is
from one point (or host computer) in the network to another point or host computer. TCP/IP and
the higher-level applications that use it are collectively said to be "stateless" because each client
request is considered a new request unrelated to any previous one (unlike ordinary phone
conversations that require a dedicated connection for the call duration). Being stateless frees
network paths so that everyone can use them continuously. (Note that the TCP layer itself is not
stateless as far as any one message is concerned. Its connection remains in place until all packets
in a message have been received.)
A workgroup or peer-to-peer network is one in which all
computers on the network can pool their resources together. Each
individual computer usually retains its control over files, folders,
and applications; however, every computer on the network can
use another’s printer, scanner, CD drive, and so on. Workgroup
networks contain a small number of computers.
Workgroups can be made up of 2, 5, or even 10 computers. It is
important to note that the more computers in the workgroup, the
slower the network may run.
A workgroup network is easy to maintain and set up. It’s also cost
effective, especially for home network use. A wide range of
cabling and networking solutions are available for your home
network. Some solutions provide fast and powerful networking;
others offer slower connections yet reliable service.
You might want to use a workgroup network in your small
business. It can be efficient if you keep the network small—ten or
fewer computers. In an office situation, people will access the
computers and the network more than in a home situation;
therefore, network traffic is likely to be higher than in the home
as well. Consider building a workgroup network with an eye
toward upgrading to a client/server network in the near future,
especially if you’ll be adding more computers to the network.
Advantages of peer-to-peer networks
The main advantage of a peer-to-peer network is that it is easier to set up and 1. Because peer-to-peer networks are Windows-based,
use than a network with a dedicated server. Peer-to-peer networks rely on the
they’re subject to the inherent limitations of
limited network server features that are built into Windows, such as the ability
Windows. Windows is designed primarily to be an
to share files and printers. Networking Wizard that automatically configures a
operating system for a single-user, desktop
basic network for you so you don’t have to manually configure any network
computer rather than function as part of a network,
so Windows can’t manage a file or printer server as
efficiently as a real network operating system.
They can be less expensive than server-based networks. Here are some of the
reasons that peer-to-peer networks are inexpensive:
Drawbacks of peer-to-peer networks
Peer-to-peer networks don’t require you to use a dedicated server computer.
Any computer on the network can function as both a network server and a
user’s workstation. (However, you can configure a computer as a dedicated
server if you want to. Doing so results in better performance but negates the
cost benefit of not having a dedicated server computer.)
2. If you don’t set up a dedicated network server,
someone may have to live with the inconvenience of
sharing his or her computer with the network..
3. The cost difference between peer-to-peer networks
and NetWare or Windows Server is less significant in
larger networks (say, ten or more clients).
Peer-to-peer networks are easier to set up and use, which means that you can 4. Peer-to-peer networks don’t work well when your
spend less time figuring out how to make the network work and keep it
network starts to grow.
5. Peer-to-peer servers just don’t have the security or
The operating system itself, either NetWare and Windows Server can cost as
performance features required for a growing
much as £160 per user. And the total cost increases as your network grows,
although the cost per user drops.
P1.4– Task 09 – Define a TCP and Peer to Peer models and the hardware necessary to provide
external access.
M1.4 – Task 10 – Define the advantages and disadvantages of operating a TCP or Peer to peer
network within a school environment.
Server computers are the lifeblood of any network. Servers provide the shared
resources that network users crave, such as file storage, databases, e-mail,
Web services, and so on. Choosing the equipment you use for your network’s
servers is one of the key decisions you’ll make when you set up a network. In
this section, I describe some of the various ways you can equip your network’s
The simple logic is: Only the smallest networks can do without at least one
dedicated server computer. For a home network or a small office network with
only a few computers, you can get away with true peer-to-peer networking.
That’s where each client computer shares its resources such as file storage or
printers, and a dedicated server computer is not needed.
In some networks, a server computer is a server computer and nothing else.
This server computer is dedicated solely to the task of providing shared
resources, such as hard drives and printers, to be accessed by the network
client computers. Such a server is referred to as a dedicated server because it
can perform no other task besides network services. A network that relies on
dedicated servers is sometimes called a client/server network. Dedicated
servers can have more than one function but as networks expand servers tend
to have a single use, file server, Intranet, Mail server, Http server, admin
server, student server, backup server etc.
Scalability: Scalability refers to the ability to increase the size and capacity of the server
computer without unreasonable hassle. It is a major mistake to purchase a server computer
that just meets your current needs because, you can rest assured, your needs will double
within a year. If at all possible, equip your servers with far more disk space, RAM, and
processor power than you currently need.
Reliability: The old adage “you get what you pay for” applies especially well to server
computers. Why spend $3,000 on a server computer when you can buy one with similar
specifications at a discount electronics store for $1,000? One reason is reliability. When a
client computer fails, only the person who uses that computer is affected. When a server fails,
however, everyone on the network is affected. The less expensive computer is probably made
of inferior components that are more likely to fail.
Availability: This concept of availability is closely related to reliability. When a server
computer fails, how long does it take to correct the problem and get the server up and
running again? Server computers are designed so that their components can be easily
diagnosed and replaced, thus minimizing the downtime that results when a component fails.
In some servers, components are hot swappable, which means that certain components can
be replaced without shutting down the server. Some servers are designed to be fault-tolerant
so that they can continue to operate even if a major component fails.
Service and support: Service and support are factors often overlooked when picking
computers. If a component in a server computer fails, do you have someone on site qualified
to repair the broken computer? If not, you should get an on-site maintenance contract for the
computer. Don’t settle for a maintenance contract that requires you to take the computer in
to a repair shop or, worse, mail it to a repair facility. You can’t afford to be without your server
that long.
A large disadvantage to being a member of a network is system security. You don’t want a child to accidentally
delete or modify data in an accounting file, for example.
When you’re sharing your equipment (such as a printer or Zip drive) over a network, you take the chance that the
equipment won’t be readily available when you need it. Say a student just sent a 24-page color document to a
networked inkjet printer. You’ll have to wait your turn to print, and that could take awhile, depending on the
network setup, printer speed, and so on.
Additionally, sharing files and applications can cause problems if two people want to use a file at the same time.
Some applications are built for more than one user to use program files at the same time; others are not.
Security of your files can be a slight problem on a workgroup network. You do, however, have the option of not
sharing all your files and folders. You can choose only those folders to which you want to grant access and share
them. Security issues are more serious in a business environment than in your home network. Sensitive files and
data (salaries, for example) must be private from the general population.
Another disadvantage is backing up the computer. With workgroup networking, each computer user is responsible
for his or her own backups. Perhaps not every user will need a backup of the data on his or her computer; however,
each user should understand the importance of backups and understand how.
And expense, a network server can cost several hundred, additional hard drives, backup software and hardware
and a lot of extra cabling all cost.
P1.5 – Task 11– Define a Client Server network and the technical hardware necessary to provide
internal and external access.
M1.5 – Task 12 – Define the advantages and disadvantages of operating a Client Server network within
a school environment.
Bluetooth - Bluetooth is the name of a short-range wireless network technology that’s designed to
let devices connect to each other without need for cables or a Wi-Fi network access point. The two
main uses for Bluetooth are to connect peripheral devices such as keyboards or mice to a computer
and to connect hand-held devices such as phones and PDAs to computers.
Bluetooth is slow — about 721Kbps, way slower than Wi-Fi networks. Bluetooth isn’t designed to
transport large amounts of data, such as huge video files. For that, you should use Wi-Fi.
3g and 4G - Based on the ITU standards, the 3G and 4G network is the current generations of
mobile networking and telecommunications. It features a wider range of services and advances
network capacity over the previous 2G network. The 3G network also increases the rate of
information transfer known as spectral efficiency. A 3G network provides for download speeds of
14.4 megabits per second and upload speeds of 5.8 megabits per second. The minimum speed for a
stationary user is 2 megabits per second. A user in a moving vehicle can expect 348 kilobits per
This scheme is known as a layered system. Each transmission features three layers of information.
The top layer is general service. The middle layer is a control data transmission. The bottom layer is
the basic connectivity information. There is a distinct difference from Wi-Fi, or IEEE 802.11
technology, and this network. Wi-Fi is basically a short range network that offers high- bandwidth
designed for data transfer. 3G networks are geared towards cellular telephone technology and
Internet access.
Wi-Fi - The common name for wireless networking using the 802.11 protocols. With wireless
networking, you don’t need cables to connect your computers. Instead, wireless networks use radio
waves to send and receive network signals. As a result, a computer can connect to a wireless network at
any location in your home or office. Wireless networks are especially useful for notebook computers.
After all, the main benefit of a notebook computer is that you can carry it around with you wherever
you go.
A wireless network is often referred to as a WLAN, for wireless local area network. The term Wi-Fi is
often used to describe wireless networks, although it technically refers to just one form of wireless
networks: the 802.11b standard.
A wireless network has a name, known as a SSID. SSID stands for service set identifier . Each of the
computers that belong to a single wireless network must have the same SSID.
Wireless networks can transmit over any of several channels. In order for computers to talk to each
other, they must be configured to transmit on the same channel.
The simplest type of wireless network consists of two or more computers with wireless network
adapters. This type of network is called an ad-hoc mode network.
A more complex type of network is an infrastructure mode network. All this really means is that a
group of wireless computers can be connected not only to each other, but also to an existing cabled
network via a device called a wireless access point, or WAP.
P1.6 – Task 13 – Discuss the technologies behind Wi-Fi, Bluetooth, 3Gand 4G
M1.6 – Task 14 - Outline the factors affecting range and speed of wireless
technologies within a school environment.
AppleTalk - Apple computers have their own
suite of network protocols known as AppleTalk
because of the language barrier between
operating systems and hardware differences.
The AppleTalk suite includes a Physical and
Data Link layer protocol called LocalTalk, but
can also work with standard lower level
protocols, including Ethernet and Token Ring.
Transmission Control Protocol (TCP): Provides reliable connection oriented
transmission between two hosts. TCP establishes a session between hosts, and
then ensures delivery of packets between the hosts.
Internet Protocol (IP): A routable protocol that uses IP addresses to deliver
packets to network devices. IP is an intentionally unreliable protocol, so it doesn’t
guarantee delivery of information. It works on the Network layer of the TCP and
communicates with these devices to provide a function, printing, internet access,
file access, communication. It does not operate applications but initiates
Several LAN systems have been created independently from each other. Ethernet
II is still used. Some years ago, the Institute of Electrical and Electronics Engineers
(IEEE) came up with a project. The aim of this project was to unify existing
initiatives and work out standards for particular LAN types (e.g. Ethernet, Arcnet,
Token Ring, etc). These standards described the Media Access Control (MAC) layer
for each type. The IEEE 802.3 standard was created for Ethernet, IEEE 802.4 for
Token Bus, IEEE 802.5 for Token Ring, and so on.
802.2 - A joint standard, IEEE 802.2, was
created for the Logical Link Control (LLC)
layer of all systems. In other words, the LAN
link layer has been divided into two sublayers. The bottom MAC layer—partially
overlapping the physical layer—deals with
access to the communication medium. The
top LLC layer enables you to initiate,
administer, and terminate logical
connections between individual LAN
802.3 or Ethernet - Ethernet has been around in various
forms since the early 1970s. The current incarnation of
Ethernet is defined by the IEEE standard known as 802.3.
Various types of Ethernet operate at different speeds and
use different types of media. However, all the versions of
Ethernet are compatible with each other, so you can mix
and match them on the same network by using devices
such as bridges, hubs, and switches to link network
segments that use different types of media.
This is pretty much the standard used in computers,
speeds vary but the technology stays the same.
802.5 – Put simply this is the network card that pushes the technology behind Token Rings.
This card addressing managed the tokens, sends the information around the network
looking for the outlet for the information and gathering in the tokens sent out by users.
When it receives the token and deals with it, the information is changed on the users
machine to indicate that the token has been received and dealt with. The card then
discards additional requests from the network to process the information again unless the
user requests that the information is different or has changed.
The User Datagram Protocol (or UDP) is a connectionless Transport layer protocol that is used when
the overhead of a connection is not required. After UDP has placed a packet on the network (via the IP
protocol), it forgets about it. UDP doesn’t guarantee that the packet actually arrives at its destination.
Most applications that use UDP simply wait for any replies expected as a result of packets sent via UDP.
If a reply doesn’t arrive within a certain period of time, the application either sends the packet again or
gives up.
Probably the best-known Application layer protocol that uses UDP is DNS, the Domain Name System.
When an application needs to access a domain name such as www.brookeweston.org, DNS sends a
UDP packet to a DNS server to look up the domain. When the server finds the domain, it returns the
domain’s IP address in another UDP packet. (Actually, the process is much more complicated than that.
FDDI - Fibre Distributed Data Interface, a 100Mbps network standard used with fibre-optic backbone.
When FDDI is used, FDDI/Ethernet bridges connect Ethernet segments to the backbone. Fibre optic
cabling and fibre optic data management is expensive but it manages large networks and traffic at a far
faster speed. The FDDI cards manage the information transfer rate along those lines, sending on further
information when the router or server receives the first sections.
P1.7 – Task 15 – Discuss the technologies behind Network Protocols.
M1.5 – Task 16 - Discuss the advantages and Disadvantages of each Protocol in a
School Environment.
802 standards
DNS - To provide a unique DNS name for every
host computer on the Internet, DNS uses a
time-tested technique: divide and conquer.
DNS uses a hierarchical naming system that’s
similar to the way folders are organized
hierarchically on a Windows computer. Instead
of folders, however, DNS organizes its names
into domains. Each domain includes all the
names that appear directly beneath it in the DNS
hierarchy. For example, on the right shows a
small portion of the DNS domain tree. At the very top
of the tree is the root domain, which is the anchor point for all domains. Directly beneath the root domain are
four top-level domains, named edu, com, org, and gov.
A DNS server is a computer that runs DNS server software, helps to maintain the DNS database, and responds
to DNS name resolution requests from other computers. Although many DNS server implementations are
available, the two most popular are Bind and the Windows DNS service. Bind runs on UNIX-based computers
(including Linux computers), while Windows DNS runs on Windows computers. Both provide essentially the
same services and can interoperate with each other. The key to understanding how DNS servers work is to
realize that the DNS database — that is, the list of all the domains, sub-domains, and host mappings — is a
massively distributed database. No single DNS server contains the entire DNS database. Instead, authority
over different parts of the database is delegated to different servers throughout the Internet.
DHCP - Every host on a TCP/IP network must have a unique IP address. Each host must be properly
configured so that it knows its IP address. When a new host comes online, it must be assigned an IP
address that is within the correct range of addresses for the subnet and is not already in use. Although
you can manually assign IP addresses to each computer on your network, that task quickly becomes
overwhelming if the network has more than a few computers.
That’s where DHCP, the Dynamic Host Configuration Protocol, comes into play. DHCP automatically
configures the IP address for every host on a network, thus assuring that each host has a valid, unique
IP address. DHCP even automatically reconfigures IP addresses as hosts come and go. The DHCP can
save a network administrator many hours of tedious configuration work.
Although the primary job of DHCP is to dole out IP addresses and subnet masks, DHCP actually provides
more configuration information than just the IP address to its clients. The additional configuration
information is referred to as DHCP options. The following is a list of some common DHCP options that
can be configured by the server:
The router address, also known as the Default Gateway address
The expiration time for the configuration information
Domain name
DNS server address
WINS server address
HTTP - The Hypertext Transfer Protocol serves for information searching on the
Internet (or intranet). A client-server relationship is the basic architecture of
communication in HTTP protocol. If a direct TCP connection between a client and a
server is established, the user types the Uniform Resource Identifier (URI) he or she
wants to survey into the browser:
The client first takes the server name from the URI and with the help of DNS, translates
it into the IP address (1 and 2). Then the client establishes a TCP connection with the
obtained IP address of the server. The browser inputs the HTTP request into the newly
created channel (3), and the server responses with an HTTP response (4) within the
same TCP connection. Then, the browser displays the response to the user.
It is important that the browser displays the web pages to the user. Every web
page usually consists of many objects and every object must be downloaded by
a separate HTTP request from the web server. Only the basic text of the web page is downloaded by the first request; the basic
text usually contains many references for objects necessary for properly displaying the web page. Thus, in the next step,
separate TCP connections with the web server are established simultaneously to download each individual object. This process
creates transmission peaks in the transmission channel. A user usually sets the browser (client) so that the responses (web
pages) will be displayed to the user and stored in a cache to reduce the response time and network bandwidth consumption on
future equivalent requests. When repeating the request, the information can be displayed to the user from the local cache.
As usual, caching has problems with fresh information. Various strategies are used to overcome the problem of when to display
cached information and when the client should transfer information from the server . It is possible for a client to ask a server by
HTTP: "Have you changed the web page?" Only if the reply is "Yes" will the page be transferred from the server. Some responses
of the server can be marked not to be stored into the cache. The client must contact the target server even if it has a cached
copy of the data being requested. This is called a HTTP server.
FTP - File Transfer Protocol (FTP) is an application protocol suitable
for file transfers in a computer network based on TCP/IP. FTP is used
for file transfers in computer networks using TCP/IP protocol. A user
works with a user interface that is represented either by the
command line of the FTP program, a GUI FTP utility, or an Internet
In the Windows world, an FTP server is integrated with Microsoft’s
Web server, Internet Information Services, or IIS. As a result, you can
manage FTP from the IIS management console along with other IIS
On UNIX and Linux systems, FTP isn’t usually integrated with a Web
server. Instead, the FTP server is installed as a separate program.
You’re usually given the option to install FTP when you install the
operating system.
When you run an FTP server, you expose a portion of your file
system to the outside world. As a result, you need to be careful
about how you set up your FTP server so that you don’t accidentally
allow hackers access to the bowels of your file server.
When you set up an FTP site, Internet Information Services creates
an empty home directory for the site. Then it’s up to you to add to
this directory whatever files you want to make available on the site.
The easiest way to do that is to simply open a My Computer window
and copy the files to the site’s home directory.
SMTP - One of several key protocols that are used to provide e-mail services. The SMTP design is based
on the following model of communication: as the result of a user mail request, the sender-SMTP
establishes a two-way transmission channel to a receiver-SMTP. The receiver-SMTP may be either
the ultimate destination or an intermediate. SMTP commands are generated by the sender-SMTP
and sent to the receiver-SMTP. SMTP replies are sent from the receiver-SMTP to the sender-SMTP in
response to the commands.
Once the transmission channel is established, the SMTPsender sends a MAIL command indicating the sender of
the mail. If the SMTP-receiver can accept mail it responds
with an OK reply. The SMTP-sender then sends a RCPT
command identifying a recipient of the mail. If the
SMTP-receiver can accept mail for that recipient it responds
with an OK reply; if not, it responds with a reply rejecting
that recipient (but not the whole mail transaction). The
SMTP-sender and SMTP-receiver may negotiate several
recipients. When the recipients have been negotiated the SMTP-sender sends the mail data,
terminating with a special sequence. If the SMTP-receiver successfully processes the mail data it
responds with an OK reply. The dialog is purposely lock-step, one-at-a-time.
P1.8– Task 17 – Discuss the technologies behind HTTP, SMTP and FTP, their functions
M1.8 – Task 18 - Outline the practical applications of using these technologies within
a school environment.
P1.1 - Task 01 – Describe the technical purposes of Workstations, Base Units and associated peripherals.
P1.1 – Task 02 – Describe different common types of networks, and in technical detail describe how information is
transferred around the system in terms of information flow.
P1.1 – Task 03 – Suggest a Network system type and workstation purchase that will suit the needs of your client.
P1.1 – Task 04 – Describe with examples WAN information transfer technologies.
P1.2 – Task 05 – Define and describe how Network topologies work and how they transfer information from station to
M1.2 – Task 06 – Suggest a Network Topology for your Client and Define and describe the benefits and
disadvantages of using this topology in a school environment.
P1.3 – Task 07 – Describe the system of CSMA and Token Passing
M1.3 – Task 08 – Explain Token Passing and CSMA in terms of how this system would benefit students within a
school environment.
P1.4– Task 09 – Define TCP and Peer to Peer models and the hardware necessary to provide external access.
M1.4 – Task 10 – Define the advantages and disadvantages of operating a TCP or Peer to peer network within a
school environment.
P1.5 – Task 11– Define a Client Server network and the technical hardware necessary to provide internal and
external access.
M1.5 – Task 12 – Define the advantages and disadvantages of operating a Client Server network within a school
P1.6 – Task 13 – Discuss the technologies behind Wi-Fi, Bluetooth, 3Gand 4G
M1.6 – Task 14 - Outline the factors affecting range and speed of wireless technologies within a school environment.
P1.7 – Task 15 – Discuss the technologies behind Network Protocols.
M1.5 – Task 16 - Discuss the advantages and Disadvantages of each Protocol in a School Environment.
P1.8– Task 17 – Discuss the technologies behind HTTP, SMTP and FTP, their functions
M1.8 – Task 18 - Outline the practical applications of using these technologies within a school environment.

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