5 - Fundamentals of Computer Networks Flashcards
Yes
Network
An interconnection of computers and other pieces of hardware to facilitate communication and the sharing of resources
Network adv and dis
Adv:
- Resources such as printers, internet connections and files can be shared, saving both money and effort
- Communication can take place via email or instant messaging
- Backing up data to a different computer is far more straightforward
Dis:
- Management of a network is a specialist skill, which can be quite expensive
- Security procedures are needed to prevent unauthorised access to a potentially large number of computers
- Network hardware, including cables and switches, can be expensive
PAN
Personal Area Network
This describes devices owned by a single user, connected via Bluetooth, such as a phone, tablet and headset
LAN
Local Area Network
This is a network covering a single building or perhaps a campus. Usually, a single organisation owns all hardware that belongs to a LAN
WAN
Wide Area Network
This would be spread over a large geographical area, with shared ownership of some hardware (a telecommunications company might own much of the cabling). The Internet is the largest example of a WAN
Wired Vs Wireless
Wired:
- More secure, as physical connection is needed, so a hacker would need to be in the building
- Less prone to interference
Wireless:
- Much easier to add a device
- No requirement to stay in the same place
Connection Media: Wireless
Radio Waves
Connection Media: Wired
Optical fibre
Can be used for very fast connections, or if lots of computers are going to share a single connection
Copper cabling
Cheaper and slower, although it is quick enough for most activities that a single computer would perform online
Network Topology
The pattern in which the hardware on a network is positioned, including connections. Common topologies include star and bus
Topology: Star
Every device is connected to a switch at the centre of the network. All communication travels via this switch
Adv:
- Very few data collisions, since each device has a dedicated line to the switch
- Strong, centralised security
Dis:
- Lost of cabling needed
- If the switch has no spare ports, adding another device can be difficult
Topology: Bus
A central cable called the backbone, running between two terminators, connects all devices
Adv:
- Uses relatively little cable, making it quite inexpensive
- Additional devices can be easily added
Dis:
- Collisions can occur, as multiple transmissions will attempt to use the shared backbone
- If a large number of devices are connected, network transmission can be slow (due to collisions)
Protocol
A set of rules that governs how a computer communicates on a network. Computers have many protocols, each necessary for a different purpose (email, accessing web pages, moving files, etc.). Without protocols, communication between computers would be impossible
Protocol: Ethernet
A family of protocols rather than a single protocol
This is a set of rules that governs how data is formatted for transmission across a LAN
Protocol: Wi-Fi
Letters aren’t short for anything, but are a brand name
These rules control how data is transmitted on WLAN
Protocol: TCP/IP
Transfer Control Protocol and Internet Protocol
These are 2 protocols that often work together
Their collective roles is to break up data into packets, each of which is a chunk of data that knows where it has been sent from and where it is to be delivered to
Protocol: UDP
User datagram protocol
Transmits data packets very quickly, but without checking to see whether each packet has arrived, so is not always reliable
Protocol: HTTP
Hyper text transfer protocol
This is the set of rules governing how hypertext (language of the WWW) is moved around the Internet, from device to device
Protocol: HTTPS
HTTP Secure
This encrypts data that is sent across the internet. Encrypted data cannot be read if intercepted, so is favoured when sending passwords or credit card numbers
Protocol: FTP
File transfer protocol
This is how files are moved from 1 computer to another across the internet. This protocol is heavily relied upon in building websites, moving files from the dev’s comp to a server, from where they can be accessed publicly
Protocol: SMTP
Simple mail transfer protocol
While POP3 might be used to retrieve emails, SMTP is used to send them from one server to another
Protocol: IMAP
Internet message access protocol
This email protocol is used to allow multiple devices (laptops, tablets, phones, etc.) to access the same email account
Internet protocol address
A unique number used to identify every device connected to the internet. No 2 IP addresses are the same. If your computer requests a web page, your computer’s IP address specifies where that web page should ultimately be delivered
Authentication
Measures to make sure that a person trying to access data is who they say they are. This can take place by way of:
- Usernames and passwords
- Memorable info, such as mother’s maiden name
- Checking that they are using a recognised IP address
Encryption
Scrambling data using a key to ensure that is makes no sense to anyone who intercepts it. When it is received, the recipient also has a key which can be used to decrypt the data, returning it to its readable form
Firewalls
These can be either hardware, software or both. A firewall can be told to block certain traffic (such as all emails or any traffic from a suspect IP address) or to only allow certain traffic (such as from a single, trusted device), blocking everything else
MAC address filtering
Each computer has a MAC (Media Access Control) address which, unlike an IP address, cannot be changed. Based on this unique identifier, specific devices can be either permitted onto, or blocked from, a network
TCP/IP model
A series of protocols. When they work together, they transmit data from one computer, through any number of pieces of network hardware, to another computer. The TCP/IP model is a concept, not a physical thing
The model has 4 layers, each containing a n.o of protocols. When data is sent, protocols at 1 layer break down and repackage the data into smaller unity, before passing the data to the layer below. When data is received, those units are reassembled as they move up the model
Application Layer
Where network apps, including browsers and email apps, operate
Protocols: HTTP, HTTPS, FTP, SMTP, IMAP
Transport Layer
Establishes comms between the sender and the recipient, agreeing on how comms will take place
Protocols: TCP, UDP
Network Layer
Packages data for transmission by breaking it into units called packets, which are sent across the network
Protocols: IP
Network Interface Layer
The physical components of the computer, such as the NIC, operate at this level
Protocols: Ethernet, Wi-Fi
