Topic 3: Networks

Server

A computer system or a software application that provides a service to other computer systems on the same network

Client

A computer system or software application that requests a services from a server connected to the same network

A computer network

• Formed when 2 or more computers are linked together.

• Every computer or device on a network can send and receive data from any of the other computers or devices connected to the network.

Hub

• Connection point for devices on a single network

• When a network device wishes to send data to another device on the network, it copies the data and sends it to all devices connected to its ports.

• This generates a lot of unnecessary traffic on the network, slowing it down.

Switch

• Similar to a hub, but can identify which device is connected to which port, allowing a network connected by switches to operate much faster

• Data is only sent to the computer that needs it

Router

• Can connect multiple networks and serves as an intermediary between them (i.e. home network and Internet)

What is the internet?

• Globally connected network system

• Uses TCP/IP protocol to transmit data

• No centralized governance

• Hosts the web pages that make up the World Wide Web

• ISPs (Internet Service Providers) run networks that provide internet access

• ISPs are “glued together” by internet exchanges (IXPs)

• IXPs are the key to connecting all the different ISPs and networks together - usually run and maintained by nonprofits

How does the internet work?

• Data travels in the form of packets.

• Every file you send or request you make is split up into packets over the internet.

• Individual packets often take different routes through exchanges, ISPs, and junction boxes

• Ultimately reach the same destination and are reassembled at destination.

Packet Switching

• A packet is a unit of information suitable for travel through computer networks.

• Data is grouped into packets.

• A file being transmitted through packet switching may be divided into multiple packets and each packet could follow a different route to the same destination.

• This allows for more efficient data transmission and reduced delays.

What does a router do on the internet?

• Used to manage traffic

• Controls the flow of data packets

• Checks address of data packets

• Puts packets on correct path

• Secure transmission

The 8 Network Topologies

LAN (Local Area Network)

• Covers a single building or collection of buildings

• Less than 1KM radius

WAN (Wide Area Network)

• Covers more distance than LAN

• Greater than 1KM radius

• Often uses multiple routers

• May be several LANs connected together

• Examples: Internet, Cellular Network, ATM network

VLAN (Virtual Local Area Network)

• 1 or more physical LAN (local area network)

• Network switch used to divide network

• Works as multiple networks

• More than the number of physical networks

• Each VLAN may have different security requirements

• Appears to an outsider as 1 LAN or WAN

WLAN (Wireless LAN)

• LAN by which devices are connected by high-frequency data waves

• Requests and responses from the internet (internet access) can be made

  through WLAN

• Uses can move around

• “Wifi network”

• Uses type of radio waves called Wifi (Wireless Fidelity)

Intranet

• Private network

• Sort of a “private internet”

• Uses TCP/IP

• Can view web pages similar to those on the internet

• Intranet web pages only accessible from computers on network

• North Korea - nationwide intranet

Extranet

Intranet that is accessible by wifi

How does a VPN (Virtual Private Network) work?

It makes a "tunneled" network through the internet or any other public network. It's considered ideal for establishing a secure connection.

What are the hardware and software components of a VPN?

1. Internet Access

2. VPN software (client, utilities, and server. Establishes the private connection)

3. VPN routers

4. VPN appliances

5. VPN concentrators (A single device to handle a large number of incoming VPN tunnels)

6. VPN servers

What does a site-to-site VPN do?

It connects two different locations securely.

What does a remote-access VPN do?

Connects an individual to a private network.

Benefits of a VPN

P2P Networks

• Allows 2 or more computers to share resources with each other

• Each computer acts as both a client and server

• No central point

What are protocols and what are their roles?

A set of rules for data transmission (packets).

Roles:

• Maintain Data Integrity - same data that is sent is received

• Flow Control - data is sent and received at the same rate

• Prevent Deadlock - two packets don’t “block each other”

• Prevent Errors - Make sure no errors introduced in transit

wifi vs ethernet

• Ethernet faster, more consistent speed, lower latency data transfer

• Wifi easier to install and deploy, cheaper

• Ethernet more secure, can only be tapped through physical access

Fiber Optics vs Copper Cabling

• Fiber - faster, more expensive, lighter, almost impossible to tap, immune to interference, longer range(40 km+)

• Copper - Susceptible to electromagnetic interference, shorter range (100m), heavier, thicker

Factors Affecting Transmission of Data

Primary Factors

• Traffic

Secondary Factors

• Time of Day

• Distance

• Infrastructure

Tertiary Factors

• Environmental Issues (Temperature, Interference)

• Financial Factors (Cheaper equipment, etc.)

• Type of Data (Size, streaming, etc.)

Lossy Compression

• Removes data

• Smaller file size - Irreversible

• Used when some data can be lost (videos, images, etc.)

Lossless Compression

• Uses algorithm to reduce file size

• Larger than lossy, but smaller than normal - Reversible

• Used when no data can be lost (text, software, etc.)

One Factor Authentication

One factor, just one thing to input (e.g., passwords)

Two Factor Authentication

Something you know (e.g., password) and something you have (e.g., phone)

Three Factor Authentication

Something you know (e.g., password), something you have (e.g., phone) and something you are (e.g., fingerprint)

What is encryption?

A method of encoding data in a way that can only be read by the sender and receiver, and requires a “key”

MAC (Media Access Control) Address

• Used to identify network-enabled devices in networks

• “Hard-coded” by manufacturer (But can be spoofed)

• Network interface controller

• Unique, 6 pairs of 2 hexadecimal digits

• Check against white list

Firewalls

• Can be hardware- or software-based

• Analyzes data packets

• Controls incoming and outgoing traffic according to predetermined rules

• Can filter based on MAC addresses

Physical Security

• Locked doors

• Cages

• Security Guards

• Secure Rooms

• Hurricane/Earthquake Proof

• EMP-Insulated