1. Networking For VCE IT By Mark Kelly Manager, Information Systems
McKinnon Secondary College
Lecture notes: Vceit.com

2. Networking
Year 11 IT – all of the topics can be covered at a relatively simple level
ITA – topologies and protocols are not in the study design and cannot be directly assessed
Software Development – all topics are relevant
Note – several complex issues have been grossly simplified in this presentation. For example, detailed differences between switches and routers at the transport level are not necessary in any VCE course and will only serve to frighten sensitive souls.

3. 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.

4. 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)

5. Why network?
Efficiency – Better, faster communication – , videoconferencing
Cost savings ( vs phone calls, physical travel),
Staff savings (e.g. networked helpdesk),
Equipment savings: printers, internet connections, internet cache, CD drives
Effectiveness – collaborative work is easier, access to resources is broader, group calendaring
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, contact)

6. LANs – local area Types of networks, by size
Geographically limited, usually to one site.
Can be cabled (usually UTP, fibre optic, coaxial) or wireless.

7. WANs – Wide Area Types of networks, by size
Broad geographic coverage (e.g. state-wide, country-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.

8. The internet 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)

9. Server-Based Networks
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 (NOS)
Controls access to data and equipment
Runs ‘community’ programs
Offers control, security, centralisation, automation

10. Peer-to-Peer (P2P) networks
No server, cheap, simple, easy to run
All users have equal authority and rights
Little protection from each other
Used at home or in small orgs with trusted users
Share files, internet connection, printer
Internet music sharing networks (e.g. Kazaa) are P2P - no central computer; data and software on users’ computers.
P2P built into Win, Linux, Mac

11. Protocols
Communication protocols are agreed sets of rules and procedures for computers to exchange information.
Like humans agreeing to speak the same language during a conversation.
For two computers to exchange data, they must be using the same protocols.

12. Human Protocols
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 question
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, Charlie etc.)

13. Network Protocols
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 (POP, IMAP)
- how to request and deliver web pages (HTTP)
- how to request and deliver files (FTP)

14. Choosing Protocols
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.

15. The King of Protocols – TCP/IP
The universal protocol for internet communications.
The backbone of the internet.
Made up of 2 complementary protocols…
TCP (Transport Control Protocol)
and
IP (Internet Protocol)

16. Protocols – TCP TCP (Transport Communication Protocol)
Breaks files into packets to be sent across the internet or a network. Each packet contains:
the address of the sender
the destination address
error-detecting checksum
a chunk of data (e.g. 1K)

17. 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 internet conditions at that time.

18. Protocols – TCP/IP TCP again…
At the packets’ destination the receiving computer’s TCP re-assembles packets back into the original file.
Recalculates checksum to see if packet is OK
If packets are damaged, lost or delayed in transit, TCP will request the server to send the packet again.

19. Packet Switching
Any protocol that breaks files into packets (like TCP/IP does) is called packet switching.
(Compare with circuit switching used by telephones where a full-time path is set up for the duration of the communication)

20. Packet Switching
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 huge transfer.
Imagine mailing a house from Melbourne to Sydney one brick at a time.

21. Addressing
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 information.
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.

22. Internet Addressing
Humans like working with names (e.g. but computers use IP numbers (e.g ).
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.

23. Addressing
Domain name servers (DNS) – a distributed database on thousands of computers across the world - convert URLs into IP addresses.
Like a phone book – look up a name (URL) to get a number (IP address).

24. NETWORKING TECHNOLOGIES
NETWORKING TECHNOLOGIES
A “Networking Technology” defines how packets are handled and what the hardware is like.
The only networking technology worth knowing is Ethernet
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.

25. 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.

26. 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 time.
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 transmits.

27. MA = Multiple Access. When one Ethernet station transmits, all the stations on the cable hear the transmission
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 transmission attempt.
The random waiting time prevents endless further collisions.

28. 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 the packet and reads its contents.
If not, the node ignores the packet.

29. Huh? Network segments?
A network segment is a self-contained section of a network bounded by a bridge, router, or switch.
Using segments reduces network congestion.
Like classrooms in a school.

30. Network Hardware The main bits of network hardware: Cables
Network interface cards (NIC)
Server (e.g. file server, proxy, DHCP, web servers)
Switches (rarely, hubs)
Routers – now SOHO (Small Office / Home Office) combined boxes contain an ADSL modem, a router, wireless access point (WAP), switch, print server, coffee maker etc)

31. 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.

32. Hardware - NIC
The Network interface card (NIC) allows a stand-alone computer to connect to a network.
Can be cabled or wireless (radio)
Often now built into motherboards
This old ‘combo’ NIC accepts both BNC (coaxial) and RJ45 (UTP) connectors.

33. Internet Choices 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 lines)
WAN Wireless (e.g. iBurst)
ISDN (no way!)

34. 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

35. Hardware – Switches and Hubs
Switches (and hubs) are connection points where cables can join up or be split.
Typically, a single incoming cable is split into multiple outgoing cables.

36. Switches and hubs Hubs and switches are the same except…
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 phone call)
Switches greatly reduce network congestion.
Come in various sizes (number of ports)

37. 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

38. Hardware – Routers 4 main roles…
Join dissimilar networks together, like a gateway (as the originalk routers used to be called)
Route packets across networks and internet
Act as a security device to guard 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.

39. 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

40. Connections – UTP
UTP (Unshielded Twisted Pair) e.g. CAT6 (‘Category 6’)

41. EXTINCT Connections – Coaxial Now extinct Shielded from interference
Thick and thin varieties
Range: Thin-185m, thick-500m
Needs terminator at end of cable
Higher data capacity than UTP
Connectors can fail
Connections – Coaxial
EXTINCT
Coaxial cable
Can be daisychained with BNC (Bayonet) T-pieces and joined with I- pieces

42. Word of Wisdom DO NOT RECOMMEND THIN OR THICK COAXIAL ALWAYS UTP (Cat6) or FIBRE OPTIC (for long distances or very high bandwidth)

43. 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
Resists EMI
Light signals bounce down Fibre Optic cable using Total Internal Reflection.

44. Connections – Fibre Optic
Core is as thin as a human hair
Not very flexible – needs thick protective coat
VERY fast
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

45. 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 cross oceans 
Warning! Sharks can damage your network!
Sharks get over-excited by the electromagnetic fields radiated by copper cable. FO is silent.

46. Connections – Wireless
Data sent as radio signals between NICs and base stations (WAP=wireless access point)
short distances (e.g. 80m-200m), reduced by obstacles
Speeds of 54Mbps and increasing
Encrypted to prevent eavesdropping

47. Wireless 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

48. Connections – Wireless
Good for temporary networks, or when PCs rarely needed in a location
Good for laptop-intensive places (e.g. classrooms, staffrooms). Great at home
Relatively expensive compared to cable, but a useful network add-on
Security concerns – never run it unsecured!
Wireless base station &
white radio antenna

49. Servers Robust central computers at the heart of a network.
File servers are the most common server type.

50. File Servers
File servers run the Network operating system (NOS) which handles:
authenticating users during login
controlling users’ access to resources based on their rights
managing print queues
doing backups
running centralised software such as virus scanners
running services like DHCP to give out IP addresses to workstations
controlling internet services

51. 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.

52. File Servers
Servers don’t really have anything special in terms of hardware.
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 (discussed soon)

53. 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) tapes.
Servers are the muscle men in the computer world

54. 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 high-quality components
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.

55. Redundant Array of Independent Disks) arrays for reliability and/or speed.
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 (spanning a logical single volume over several physical disks for greater performance – several simultaneous disk reads/writes are possible).
RAID disks are usually "Hot Swap“ – no server downtime to replace sick disks.
EXPENSIVE – needs justifying for small org
R.A.I.D.
3-disk RAID array

56. Server farms
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
servers –handle

57. Network Topologies
A network topology is a logical (idealised) shape of a network’s wiring. The main topologies:
Bus
Star
Tree*
Ring*
Mesh*
Each has its pros and cons: cost, complexity, reliability and susceptibility to congestion.
*not examinable

58. Bus Topology
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!

59. Bus Topology Relatively cheap and easy to install
Don't require much cabling
Gets congested with too many nodes
Not good for schools
OK for small LANs
NEED COAXIAL CABLE AND NICs so is EXTINCT nowadays!

60. * 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 for small networks!

61. Tree Topology* 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 incoming cable.
*not examinable

62. Mesh Topology* Multiple routes from one node to any other.
Hardly ever found cabled in real-life in real networks: really only appears in The Internet to give near-perfect reliability.
DO NOT RECOMMEND IT IN A TYPICAL CASE STUDY
*not examinable

63. Network Physical Security
Network Physical Security
File server failure can severely affect network users.
Server security:
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

64. Network Electronic Security
Network Electronic Security
Passwords are not strong protection – they can be guessed, forgotten or stolen.

65. Network Security
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.

66. Encryption A form of Electronic Security
Encryption
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.

67. Network Security
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 servers etc. Keep scanners up to date.

68. Remember Exam case study will be a small organisation’s LAN.
Choose between P2P or Client-Server
If Client-Server, choose NOS - MS Server 2003
Recommend…
STAR topology, not bus
UTP - CAT5e or CAT6 cable, not coaxial
SWITCHES, not hubs
Wireless is now pretty cheap, reliable and flexible

69. Thanks! Mark Kelly VCEIT Lecture Notes: McKinnon Secondary College
VCEIT Lecture Notes:
vceit.com