Unit 3: Networks

Network types

acronym definition
PAN Personal area network: The devices around your person communicating with each other. Commonly utilizing Bluetooth. Devices include phone, watch, fitness device, possibly a laptop or hotspot.
LAN Local area network: The devices within your property communicating with each other, eg within the home, on the school campus, the office building. Commonly using wireless or hard wired Ethernet cabling.
VLAN Virtual local area network: For security and organisational reasons, typically larger organisations will split their LAN into several VLANs. For instance, the school might have a Students VLAN and a Staff VLAN, each of which grant access to different files/resources on the network
WLAN Wireless local area network. Same as a local area network but just utilizing wireless technologies. Eg: what you, the students, get to enjoy here at school ;-)
MAN Metropolitan area network. Yeah… a bit ambiguous… when is it a MAN and when is it a WAN? You tell me then we’ll both know :-p MAN is limited to a metropolitan geographical region.
WAN Wide area network. Multiple properties connected together over a long distance connection, most commonly fibre optic cable. Could be a MAN, could also be interstate, intercontinental etc.
SAN Storage area network: Network based storage
VPN Virtual private network: Establishing a connection to a remote network but granted access as if you are physically present. Discussed further later
Internet Ummm… the internet!
Extranet Extranet: Authenticated & authorised access via the public internet to secure services hosted by a network, eg: logging on to your banks website

Network topologies

Toplogies may be used to describe the physical or logical layout/structure of a network. The names are fairly loose definitions, most networks these days are a blend of these traditional topologies.

Image: NetworkTopologies.png: Maksimderivative work: Malyszkz [Public domain], via Wikimedia Commons


The need for standards

Standards ensure compatiblity

Define protocol

Roles: data integrity, flow control, deadlock resolution, congestion, error checking

Standards in networking are recorded in documents known as RFCs (request for comment).


Layers of network communication

The layers of network communicaion is known as the OSI (open systems interconnect) model. Each layer has a range of protocols that are commonly used.

An example of the different layers in action between the Spotify App on your device, and Spotify HQ.


The TCP/IP stack

TCP/IP is an amalgamation of two protocols: TCP (transport control protocol) and IP (internet protocol).


Protocols: TCP & UDP

Layer: Transport

TCP and UDP are transport layer protocols, responsible for packet switching and delivery.

Both TCP and UDP are protocols used for sending bits of data — known as packets — over the Internet. They both build on top of the Internet protocol. In other words, whether you are sending a packet via TCP or UDP, that packet is sent to an IP address. These packets are treated similarly, as they are forwarded from your computer to intermediary routers and on to the destination

TCP (Transport Control Protocol) guarantees the recipient will receive the packets in order by numbering them. The recipient sends messages back to the sender saying it received the messages. If the sender does not get a correct response, it will resend the packets to ensure the recipient received them. Packets are also checked for errors. TCP is all about this reliability

UDP (User Datagram Protocol) just sends packets to the recipient. The sender will not wait to make sure the recipient received the packet — it will just continue sending the next packets. If you are the recipient and you miss some UDP packets, too bad — you can not ask for those packets again. There is no guarantee you are getting all the packets and there is no way to ask for a packet again if you miss it, but losing all this overhead means the computers can communicate more quickly. UDP is used when speed is desirable and error correction is not necessary. For example, UDP is frequently used for live broadcasts and online games.

Packet switching animation

A TCP joke:

Hello, would you like to hear a TCP joke?
Yes, I'd like to hear a TCP joke.
OK, I'll tell you a TCP joke.
OK, I'll hear a TCP joke.
Are you ready to hear a TCP joke?
Yes, I am ready to hear a TCP joke.
OK, I'm about to send the TCP joke. It will last 10 seconds, it has two characters, it does not have a setting, it ends with a punchline.
OK, I'm ready to hear the TCP joke that will last 10 seconds, has two characters, does not have a setting and will end with a punchline.
I'm sorry, your connection has timed out... ...Hello, would you like to hear a TCP joke?

A UDP joke:

I know a UDP joke, but you might not get it.

Credits:


Protocol: IP

Layer: Network

The Internet Protocol (IP) is the method or protocol by which a packet of data is sent from one computer to another on the Internet. A packet is a small amount of data sent over a network. Similar to a real-life package, each packet includes a source and destination as well as the content (or data) being transferred. When the packets reach their destination, they are reassembled into a single file or other contiguous block of data.

So while the Internet Protocol is most well known for being the basis of the “IP address”, the Internet Protocol is more than just addresses. It governs the structure of the actual data payload (the actual information being sent) and all the associated information that packet needs to get from one computer to another (the IP addresses being part of that).

There are currently three differnt ways the Internet Protocol is being used on the internet

While the exact structure of a packet varies between protocols, a typical packet includes two sections — a header and payload. Information about the packet is stored in the header.

For example, an IPv6 header includes the following fields:

The payload section of a packet contains the actual data being transferred. This is often just a small part of a file, webpage, or other transmission, since individual packets are relatively small. For example, the maximum size of an IP packet payload is 65,535 bytes, or 64 kilobytes. The maximum size of an Ethernet packet or “frame” is only 1,500 bytes or 1.5 kilobytes.

Explainer:

Credits:


Protocol: HTTP

Layer: Application

Let’s take a closer look at one common protocol, HTTP


Other Protocols

Some other protocols that are useful to have an understanding of are:


VPNs (Virtual Private Networks)

A VPN (virtual private network), is a software tool that provides an encrypted “tunnel” over the open internet for you to connect and interact with a remote network as if you were physically and presently connected to it.

An extranet is a range of services a network makes available for clients to access externally. They are not treated (granted the privileges) as if they were physically present on the LAN.

What is a VPN? We’ll let Linux explain,

VPN properties

VPN security features:

Evaluate VPNs


Why network speeds can vary


Compression

Class exercise: How does loss-less compression work?

Demonstration:

how much wood could a woodpecker peck, if a woodpecker could peck wood!

Your turn:

she sells sea shells by the sea shore. the shells she sells are surely seashells. so if she sells shells on the seashore, i’m sure she sells seashore shells.

By the way, my current record holder is Chetan from my 2018 class who compressed the 157 characters to 70 including the dictionary. That’s 44.5% of original size. Can you beat his record?


Characteristics of transmission media

The Internet: Wires, Cables & Wifi (code.org) https://www.youtube.com/watch?v=ZhEf7e4kopM Compare Coax, Twisted pair & Fibre (4:30m) https://www.youtube.com/watch?v=EOCme3sNqws 


Wireless networking

Advantages & disadvantages of wireless networks

Discuss in relation to:

Some positives

Some negatives


Components of wireless networks


Characteristics of wireless networks

History nerd time: Where does the name 802.11 come from?

Credits:


Security

Key issues to discuss:

Advantages and disadvantages of network security methods


Review questions