Network Communications

About the Network side of Computer Science

DataBase Server

Firewall

Internet/ISP

Laptop

File Server

Modem

Router

Switch

Tablet/phone

WAP (Wireless Access Point)

Workstation

Types of networks

Centralised, Distributed

What is a centralised network and characteristics

all runs of central device, exposed to attacks

What is a distributed network and characteristics

decentralised network/All devices working together, data sent through mesh network, made up of independently operated networks, distributed packet switched network, any device can communicate with any other device

How do devices communicate with each other?

Binary (0’s and 1’s)

How can binary be sent

Electricity, Light, Wireless (generally on = 1, off = 0 with timer)

Data via electricity (how, pros and cons)

Unshielded twisted pair (UTP) e.g. ethernet, + Cheap, - high signal loss

Data via light (how, pros and cons)

Fibre optic cable, + fast, barely any signal loss, - expensive and hard to work with

Data via Radio (how, pros and cons)

Wireless machines emitting radio waves (e.g. WAP) + mobile, - short range

What is a protocol and what does it allow

a well known set of rules and standards used to communicate between machines allowing the internet to adapt and absorb new technologies

What is DNS

Domain Name system, associates links with IP addresses, computer uses DNS to find correlated IP for links.

How is DNS set up

Distributed hierarchy, split up major domains (.com, .org etc)

What is the problem with DNS

public open communication protocol, susceptible to cyber attacks (spoofing where hacker changes correlated IP for a link sending user to a fake site)

How does data travel

Data is broken down into IP Packets (addressed and return address), routers manage and move packets (send them on cheapest path) TCP ensures everything is sent, destination reorders packets

Whys is sending data reliable

Router has multiple paths, making it fault tolerant and able to change paths based on traffic, routers and TCP are scalable (more routes and routers = more reliable) and won’t interrupt service

What is TCP and it’s role

Transmission Control Protocol, manages sending and receiving of data, checks all packets arrive (otherwise won’t verify and server resends missing packets)

Explain the layers of the networking system

HTTP and DNS manage sending + receiving web files, TCP/IP and routing breaks down and transports packets, packets are made up of Binary code that’s sent physically (electricity, wireless, light)

What does URL stand for

Uniform Resource Locator

What is HTTP

Hyper Text Transfer Protocol, language used to talk between browser and servers, made up of get requests (get {name of doc}), images and files require separate get requests. For device sending info (filling details into form) sends Post request in plaintext

what is HTML

Hyper Text Markup Language, language telling browser how to make page look

What are cookies

Associates login with ID number to save users info and is automatically attached to requests

Risks of HTTP and safety methods

all in plain text so people are able to see if you send personal info, SSL, TLS, and HTTPS

What is SSL and TLS

Secure sockets layer, Transport Layer Security, request private channels that add layer of security

What is HTTPS

Hyper Text Transfer Protocol Secure, provides digital certificate for site that confirms legitimacy (handed out by trusted entities that verify sites) if no certificate, browser warns

Printer

What is a Network

A number of electronic devices connected together so they can communicate and share data

What are the reasons for a network

share files, data and resources, communicate between users, central repository for data

Stages of a network

1. sending device sends data

2. coms device encodes data for transmission

3. transmission channel - method for physically transfer data

4. com device decodes data into form receiving can understand

5. receiving device receives data

Layers of TCP/IP model

split functionality of network into different stages, each layer for different sending data aspect

What is UDP

User Datagram Protocol, doesn’t establish a connection before sending data, allowing it to start transmitting immediately, does not guarantee delivery, order, or error correction. Packets can be lost, duplicated, or arrive out of sequence, faster than TCP (online gaming, live streams)

Network layer of TCP IP Model, protocols and devices

allows data to travel across interconnected networks, manages routing, addressing and packet forwarding, sends and receives packets, protocol: HTTP, devices: Web Server

Transport layer of TCP IP Model, protocols and devices

manages end to end communication, ensures data delivered reliably, handles flow control, error correction and segmentation of data into packets, protocols: UDP and TCP, devices: Firewall

Internet layer of TCP IP Model, protocols and devices

directs network traffic, addresses and routes packets, protocol IP, devices: router

Application layer of TCP IP Model, protocols and devices

defines protocols for communication, allows users and applications to interact with network

What is IP

Internet protocol, fundamental protocols that allow network to function, provides devices unique identifiers, allows other devices to share data

Differences of IPv4

32 bit address, 4 groups (each a byte) separated by full stops, 2 parts: Network ID 1st 3 octets(indicates network), Host ID last octet (indicates device, router is 1), 4 bil unique addresses (2³²)

Differences of IPv6

340 Undecillion unique addresses (2¹²⁸), 128 bit hexadecimal, 8 16 bit quartets (alphanumeric) separated by colons, omits leading 0’s as ::

What is subnetting

dividing large networks into smaller logical networks called subnets

How does subnetting work

departments assigned individual subnets, department devices communicate on subnet, interdepartment traffic goes through router, broadcast traffic limited to each subnet,

Necessity of subnets

enables single IP networks to be divided into smaller logical networks, efficient IP usage, improved performance, enhanced security and manageability

What is a subnet mask

a 32-bit number used in IP addresses to separate network portion from host portion, determines which part refers to network and which part refers to location.

Benefits of subnetting

Better security: Isolates departments preventing unauthorised access, traffic prioritisation: critical subnets have priority, Easier maintenance: smaller segmented networks easier management

Drawbacks of Subnetting

Extra Overhead: each subnet wastes two IP addresses (subnet ID, direct broadcast ID) Higher Cost: requires extra devices, Extra Complexity: extra steps and planning

What is transmission medium and types

method used to physically move data (electricity (UTP/Ethernet), light (fibre optic) radiowaves (wireless))

What are the network components

Transmission media, Router, Switch, WAP, Firewall

What is a router

directs data between networks, uses destination IP to send data on it’s net leg of journey to destination, operates at internet layer.

What is a Switch

connects several devices together using UTP to form network, records MAC address and port of each device to send packets, part of network layer

What is a WAP

Wireless Access Point, allows devices to wirelessly connect to network, allows flexibility (num of devices not limited to physical ports, devices have freedom to move), network layer

What is a firewall and role

prevents unauthorised access to network, monitors and records network traffic ensures meets organisation security rules, blocks traffic, Internet transport layers

Need for network security

prevents people accessing confidential info (user data, business info, personal/business financials) prevents malicious actors disrupting network services, prevents damage to physical infrastructure,

Methods for network security

Monitor traffic (prevent and allow), authenticate users, encrypt network traffic an documents on network

Role of operating systems

provides authentication (only authorised users access), monitors for vulnerabilities, analyses usage patterns to detect anomalies, takes measures to prevent attacks, manages utilities such as anti malware software

what is the point of network diagrams

shows logical design of network, indicates devices and order

What is bandwidth and how is it measured

Maximum transmission capacity of a device measured by bit rate (num of bits/second in Kbps, Mbps or Gbps) or latency (time it takes for bit to travel from one place to another)

What happens when Bandwidth is increased

more data sent/received at once, faster downloads, smooth streaming, better performance

What happens when Bandwidth is decreased

increased loading times, buffering and congestion

What is network design

Process of planning computer networks to meet user and organisation requirements.

What does network design include

selecting hardware, topology, protocols, security measures. make network efficient, reliable, scalable, designed using network diagrams

What is a data collision

when 2 or more devices attempt to transmit data on same network channel at same time, leading to signal interfering and corrupting data

where does data collision occur and what happens

on shared networks, data discarded and resent, frequent collisions reduce network efficiency, performance, lead to higher latency and congestion

What is CSMA/CD

Carrier Sense Multiple Access with Collision Detection, devices listen before transmit for clear channel, then transmit. if collision occurs it stops transmitting, waits, then resends data

How to reduce data collisions

switches instead of hubs (separate collision domains), full duplex communication (simultaneous send/receiving to stop collisions) improved network design and segmentation

What is Excess Traffic and impact

high volume of broadcast messages sent over the network, causing congestion and potential collisions. Leads to reduced Throughput (successful data sent in time period) increased latency, network congestion

what is a broadcast message

sent to every device on a network segment, all devices process broadcast, too many broadcast overload network

Causes of excess traffic

large network with no segmentation, misconfigured devices/protocols, excessive use of broadcast messages

how to reduce network traffic

router to separate network and broadcasts, replace hubs with switches (limit unnecessary traffic), config devices and protocols correctly

What is a WAN

a wide area network is a large computer network that connects groups of computers over large distances. The Internet itself is considered a WAN.

What is a LAN

A local area network (LAN) is a network confined to a small, localised area. Home WiFi networks and small business networks are common examples of LANs.

What is a WLAN

A wireless LAN (WLAN) is a type of LAN that uses wireless communication to connect any type of network client or device. e.g. Wi-fi