Networking For Information Processing and Management
For Information Processing and Management
Manager, Information Systems
McKinnon Secondary College
Lecture notes: Vceit.com
What is a network – should I panic?
At its simplest, a network is two or more
computers that are connected so they can
exchange information and share resources.
Types of networks
Networks can be classified by:
•Their size (LAN, WAN, Internet);
•Their servers (Client-Server, P2P);
•The rules they use to exchange data (protocols – TCP/IP).
•How they are linked together (cable, wireless);
•Their „logical‟ shape (bus, star, tree);
•How network messages travel (Ethernet‟s CSMA/CD)
Efficiency – Better, faster communication – email, videoconferencing
•Cost savings (email vs phone calls, physical travel),
•Staff savings (e.g. networked helpdesk),
•Equipment savings: printers, internet connections, internet cache, CD
Effectiveness – collaborative work is easier, access to resources is broader,
Management - control over internet & printing, staff monitoring
Company image and “reach” – internet visibility makes any company
international and accessible and “with it”
Customer service – many more ways to help customers (e.g. FAQ,
downloads, online advice, email contact)
Types of networks, by size
LANs – local area
•Geographically limited, usually to one site.
•Can be cabled (usually UTP, fibre optic, coaxial) or
Types of networks, by size
WANs – Wide Area
•Broad geographic coverage (e.g. state-wide,
•Connections use landline data cables (e.g. ISDN,
ADSL), microwave, satellite.
•Virtual Private Networks (VPN) can form a private
network using the internet as a communication
channel – much cheaper than leased ISDN lines.
Made up of inter-networked WANs.
No central boss. Users make and enforce rules.
Uses all forms of media
Mesh topology (many possible routes from A to B)
• Client/Server model
• Automatically a pretty expensive choice
compared to P2P
• File server at the heart of the network
– Server runs the Network Operating System
– Controls access to data and equipment
– Runs „community‟ programs
– Offers control, security, centralisation,
Peer-to-Peer (P2P) networks
• No server, cheap, simple, easy to run
• All users have equal authority and
• Little protection from each other
• Used at home or in small orgs with
• Share files, internet connection,
• Internet music sharing networks (e.g.
Kazaa) are P2P - no central
computer; data and software on
• P2P built into Win, Linux, Mac
Communication protocols are
agreed sets of rules and
procedures for computers to
Like humans agreeing to speak
the same language during a
For two computers to exchange
data, they must be using the
•during a phone call, saying “Uh
huh”, “Mmmm” or “Yeah” while the
other person speaks
•nodding to show understanding
•waiting for the other person to
stop talking before you start
•raising pitch of voice after a
•airline pilots speak English, refer
to heights in feet, agree on which
direction to turn to avoid collision,
pronounce 9 as “niner”, spell out
letters with words (Alpha, Bravo,
There is a standard protocol for each network
communication task, such as:
- how to send data over the Internet (TCP/IP)
- how to send and receive email (POP, IMAP)
- how to request and deliver web pages (HTTP)
- how to request and deliver files (FTP)
Sometimes there is more than one choice of protocol for
a task, such as how messages pass across a network
(IPX/SPX vs TCP/IP, POP vs IMAP).
As long as all the connected computers use the same
protocol, it really does not matter which protocol is used
(like diplomats agreeing on a language for negotiations)
The internet only works because TCP/IP, POP, FTP and
HTTP are universal standards, used by all shapes and
sizes of computers.
The King of Protocols – TCP/IP
The universal protocol for internet
The backbone of the internet.
Made up of 2 complementary
TCP (Transport Control Protocol)
IP (Internet Protocol)
Protocols – TCP
Breaks files into packets to be sent
across the internet or a network.
Each packet contains:
-the address of the sender
-the destination address
-a chunk of data (e.g. 1K)
Protocols – TCP/IP
IP (Internet Protocol)…
Once a file has been chopped into
packets, the IP protocol delivers each
packet to its destination.
•each packet can take a different route from
A to B, bouncing from router to router
getting more precise with each hop.
•the route is dynamically chosen for each
packet, based on on internet conditions at
Protocols – TCP/IP
At the packets‟ destination the receiving
computer‟s TCP re-assembles packets back
into the original file.
Recalculates checksum to see if packet is
If packets are damaged, lost or delayed in
transit, TCP will request the server to send
the packet again.
Any protocol that breaks files into
packets (like TCP/IP does) is called
(Compare with circuit switching used by
telephones where a full-time path is set up for
the duration of the communication)
Why use packet switching?
•A single bad bit in a file can ruin an entire file.
•It‟s quicker to re-send a portion of the file rather
than the whole file.
•Important with „noisy‟ and unreliable
communication paths, such as dial-up modem.
•Many computers get to transmit some data,
rather than 1 PC tying up a channel for ages with a
•Imagine mailing a house from Melbourne
to Sydney one brick at a time.
•Like telephones, every node on a network must have
a unique identifier so the file server knows who is
requesting information, and who is to be sent
•This unique network address is hardwired into the
network card of each computer.
•Also, every active node of the internet needs a unique
identifying address so TCP/IP knows where packets
are to be sent.
•This is an Internet Protocol, or IP address.
Humans like working with names (e.g.
www.microsoft.com) but computers use IP numbers
IP address has four „octets‟ separated by dots, each
octet can be between 0 and 255.
Remember - all internet communications use IP
addresses, not URLs. Only humans use URLs.
Domain name servers
(DNS) – a distributed
database on thousands of
computers across the
world - convert URLs into
Like a phone book – look
up a name (URL) to get a
number (IP address).
A “Networking Technology” defines how
packets are handled and what the
hardware is like.
The only networking technology worth knowing
•Used everywhere by everyone (except a few odd
people who aren‟t worth worrying about)
•Uses coaxial, UTP, fibre-optic cable, and wireless.
Ethernet defines both protocols (CSMA/CD) and cabling
(e.g. UTP, thick coax, fibre), speeds etc.
Ethernet – 10Base-huh?
10Base-T=twisted pair (e.g. UTP). 10Mbps, max length
100m, RJ45 connectors.
10Base2 = uses thin coaxial (RJ58) cable – max length
195m. 10 Mbps. BNC connectors.
10Base5 = uses thick coaxial – max length 500m. Used
mainly for backbones, cable TV.
10Base-F – fibre optic cable on 10Mbps networks – can get
up to 2,000 megabits/sec (2Gbps) on the right network.
10Base-35 – broadband coaxial cable. Max length 3,600m.
How Ethernet Works
Network devices compete for attention using Carrier Sense
Multiple Access with Collision Detection (CSMA/CD).
Keep in mind: Only one signal can travel down a cable at a
CS = Carrier Sense. Before transmitting over the
network, a computer first "listens" and waits until there is
no activity on the cable. When it sees its chance, it
•MA = Multiple Access. When one Ethernet station
transmits, all the stations on the cable hear the
•CD = Collision Detection. Carrier sense does not
guarantee that two devices will not sense the same
silence and transmit simultaneously, and cause a
„collision‟. CD detects this event.
•Each node involved in the collision waits a random
number of milliseconds, then repeats the
The random waiting time prevents endless further collisions.
A „node‟ is any device attached to a network that
is capable of requesting and sending packets
(e.g. Usually a PC, network printer)
When a node wants to communicate to another
node, it transmits its addressed packet.
The packet travels to every node on the segment.
Each node inspects the packet to see if it is
addressed to him.
If so, the node opens
If not, the node ignores
the packet and reads
Huh? Network segments?
A network segment is
section of a network
bounded by a bridge,
router, or switch.
Like classrooms in a
The main bits of network hardware:
•Network interface cards (NIC)
•Server (e.g. file server, proxy, DHCP,
•Switches (rarely, hubs)
•Routers – now home models have
ADSL modem, wireless access point,
switch, print server, coffee maker)
The modem Modulator/demodulator
Modulate = turn digital data into analogue sound for transmission over
phone network. (when uploading)
Demodulate (when downloading) = convert sound back to digital data.
Transmission speed is measured in bits per second (not bytes per second!)
56Kbps modem downloads at a theoretical maximum of approx 56,000 bits
per second (about 7KB/sec). Can only transmit (upload) at 33.6kbps. 30
Hardware - NIC
•The Network interface card (NIC) allows a
stand-alone computer to connect to a
•Can be cabled or wireless (radio)
•Often now built into motherboards
This old „combo‟ NIC
accepts both BNC
(coaxial) and RJ45
Not all options are available to everyone, especially those not in major cities
• ADSL, ADSL2 (256Kbps-24Mbps)
• Cable (up to 5Mbps)
• Satellite – 1 way or 2 way
• Dialup (analogue, 56Kbps over phone
• WAN Wireless (e.g. iBurst)
• ISDN (no way!)
Hardware - NIC
•Network Interface Card
•Rated by speed: 10, 100, or „Gigabit‟ 1000Mbps.
•For a NIC to work at its maximum speed, all the other
network devices between it and the server must have
at least the same bandwidth (data-carrying capacity).
•„Auto-sensing‟ e.g. 10/100/1000 NICs adjust
themselves to the best possible speed.
•Tip: go for GIGABIT NIC in servers
Switches and Hubs
Switches (and hubs) are
connection points where
cables can join up or be
Typically, a single
incoming cable is split
into multiple outgoing
Switches and hubs
Hubs and switches are the
Dumb Hubs pass along all
network traffic they receive
(e.g. PA system)
Switches (“switching hubs”)
are clever enough to only
pass on relevant network
traffic to recipients (like a
Switches greatly reduce
•Come in various sizes 35
(number of ports)
WISDOM for U4O2 and exam
• NEVER recommend hubs!
• Switches are always best (unless an org has a free hub
available for a tiny LAN)
• No cost difference anyway
• Switches make a network far faster
HANDY SWITCH OPTIONS
• Some switches have a fibre optic port
• Some have a gigabit port
Hardware – Routers
• 3 main roles…
• Route packets across networks and internet
• Security device that guards the connection between a
LAN and the outside world (another LAN or a WAN.)
• Divide LANs into self-contained, protected areas, e.g.
admin / student networks in a school.
Hardware – Routers
• Act as a firewall at home, replacing software
firewalls like Zone Alarm
• Can be programmed to only allow authorised
incoming and outgoing traffic. E.g. can block
certain sites, forbid MP3 music files to enter.
• Most home routers also have a built-in mini-
switch but remember … a switch is not a router!
• Home routers often combine: switch, ADSL
modem, print server
Connections – Coaxial
•Thick and thin varieties
•Needs terminator at
end of cable
•Higher data capacity
•Can be daisychained with BNC (Bayonet) T-pieces than UTP
and joined with I- pieces
•Connectors can fail
Word of Wisdom
THIN OR THICK
ALWAYS UTP or FIBRE OPTIC
Connections – Fibre optic
•Made of glass (or plastic)
•Optical, not electrical – little signal fade
•Optical Signals created by LED or laser
•Multiple signals on a single fibre
•Light signals bounce down Fibre Optic cable using Total 42
Connections – Fibre Optic
•Core is as thin as a human hair
•Not very flexible – needs thick protective coat
•VERY high bandwidth
•Very secure (can‟t be tapped or snooped)
•VERY long distance (>2km without repeaters)
•Light weight, small size
•Expensive adaptors to convert digital <> electrical signals
Connections – Cables and wireless
Many fibre optic cable („FOC‟) threads can be bound into
a slim, single cable without their signals interfering with
each other, giving massive data throughput.
FOC is replacing old, heavy, expensive copper cables to
Warning! Sharks can damage your network!
Sharks get over-excited by the electromagnetic fields
radiated by copper cable. FO is silent.
Connections – Wireless
Data sent as radio signals between NICs
and base stations (WAP=wireless access
-short distances (e.g. 80m-200m),
reduced by obstacles
-Speeds of 54Mbps and increasing
-Encrypted to prevent eavesdropping
•Many PCs can connect to a base
station, share its bandwidth
•PCs can “roam” and will
automatically connect to the base
station that has the strongest signal
•Wireless NICs and antennae now
built into laptops
Connections – Wireless
• Good for temporary networks, or
when PCs rarely needed in a location
• Good for laptop-intensive places
(e.g. classrooms, staffrooms). Great
• Relatively expensive compared to
cable, but a useful network add-on
• Security concerns – never run it
Wireless base station &
white radio antenna 47
Robust central computers at the
heart of a network.
File servers are the most common
File servers run the Network operating system
(NOS) which handles:
•authenticating users during login
•controlling users‟ access to resources based on their
•managing print queues
•running centralised software such as virus scanners
•running services like DHCP to give out IP addresses
• controlling internet services 49
Network Operating Systems
The most popular NOSes are:
•Novell Netware (better, more expensive at first,
cheaper over time)
•Microsoft Server 2003 (now dominant)
They offer similar services.
Servers don‟t really have anything special in terms of
Expensive because of their high-quality components,
and “scalability” (expandability).
•Memory – servers love lots of RAM.
•Storage –need large and fast hard disks – often RAID
File Servers vs Desktops 1
•CPU Processing power – not very important in a file server
•Backup – most servers have inbuilt high-capacity tape
backup drives to protect against data loss. Tape drives usually
use QIC (Quarter Inch Cartridge) DAT (Digital audio tapes)
Servers are the muscle men in
the computer world
File Servers vs Desktops 2
Connectivity – servers often have two or more gigabit NICs to
increase their data-throughput.
Robustness - servers run all day for years, and need rugged
Scalability –the ability to increase the size and power of
equipment and networks as required e.g. add 8 hard disks,
two power supplies, two NICs, two CPUs, lots of RAM etc.
Designing and engineering this expandability is expensive.
Redundant Array of Independent [or
Inexpensive] Disks) arrays for reliability
RAID uses a group of hard disks that work
as a single disk under a RAID controller.
Flavours of RAID: RAID0 to RAID10 (RAID
1 + RAID 0) offer reliability and/or speed
(at ever-increasing cost). Includes
mirroring (for reliability) and striping (for
speed). 3-disk RAID array
RAID disks are usually "Hot Swap".
EXPENSIVE – needs justifying for small org 54
On smaller networks, network services are
performed by software in a single server.
On busy LANs, multiple servers share the work…
•Login servers – authenticate users
•Proxy servers – cache downloads
•DHCP servers – allocate IP addresses
•Print servers –manage print job queues
•Web/FTP servers – serve web pages or files
•Email servers –handle email
A network topology is a logical (idealised) shape of
a network‟s wiring. The main topologies:
•Star Each has its pros and cons:
cost, complexity, reliability
•Tree* and susceptibility to
Many devices connect to a
single cable backbone
cable as a daisychain. If the
backbone breaks, the entire
segment fails – like
Christmas tree lights.
DO NOT RECOMMEND IT
IN THE EXAM! 57
•Relatively cheap and easy
•Don't require much cabling
•Gets congested with too
•Not good for schools
•OK for small LANs
•NEED COAXIAL CABLE
* Star Topology *
•central connection point (a
switch) with cables branching
to many computers.
•Not a server with 4 NICs!!!
•If a cable fails, only one
node will fail.
•prone to traffic bottlenecks
at the centre of the star
•RECOMMEND THIS! 59
Combines bus and star topologies.
It looks like a tree.
Very common in larger networks.
e.g. one cable from a file server leads to a 24 port switch.
Many cables branch from this switch to the computers in
the computer room. They share the bandwidth of the
Multiple routes from one node to any other.
As used by The Internet to give near-
Network Physical Security
File server failure can severely affect network users.
•Locked in air-conditioned, alarmed room with barred
windows, restricted keys
•No user access to server
•Uninterruptible power supply (UPS) protects against
blackouts, brownouts and voltage spikes.
•Accessible fire fighting equipment.
•Locked floppy disk drives
Network Electronic Security
Passwords are not strong protection – they
can be guessed, forgotten or stolen.
Daily backups are vital. Massive cost and
effort to recover a single megabyte of lost data.
Organisations need a data disaster recovery
plan so they know what to do to recover from
catastrophic data loss.
•A form of Electronic Security
•Makes data unreadable to unauthorised people
even if a file is stolen.
• Web browsers use encryption to connect to a
“Secure” SSL (Secure Socket Layers) site.
TROJAN HORSES attempting to report „home‟ or start a
DOS/DDOS attack - can be blocked by a firewall.
FIREWALLS in hardware (routers) or software (e.g.
Zone Alarm) check for unauthorised incoming or
outgoing network traffic, e.g. port scanning, being
enslaved to help with a distributed denial-of-service
(DDOS) or spam attacks.
VIRUSES can disclose user passwords, steal
information, destroy data, install “back doors” to let
hackers in, clog print queues, disrupt Internet traffic,
overload email servers etc. Keep scanners up to date.
• Exam case study will be a small organisation‟s LAN.
• Choose between P2P or Client-Server
• If Client-Server, choose NOS - MS Server 2003
– STAR topology, not bus
– UTP - CAT5e or CAT6 cable, not coaxial
– SWITCHES, not hubs
– Wireless is now pretty cheap, reliable and flexible
McKinnon Secondary College
IPM Lecture Notes: