IBCS Topic 3 - Networks

Network

Collection of devices connected (wired or wirelessly) to communicate and share resources

LAN (Local Area Network)

Network connecting a small # of devices to a small physical/geographical area. Can span a few close buildings.

WAN (Wide Area Network)

Network that connects 2 or more LANs over a large physical/geographical distance through telephone/satellite/radio. The Internet is a WAN.

VLAN (Virtual LAN)

Network of computers that act as if they are connected by the same wire → may be physically located elsewhere. VLAN is accomplished through software.

SAN (Storage Area Network)

Network of storage devices that can be accessed by multiple computers as if stored on a local disk. An efficient method to increase network usage.

VPN (Virtual Private Network)

Network that uses public telecommunication infrastructure, like the Internet, to provide secure access to a network. Mimics a more expensive private network without breaking the bank.

Advantages of a VPN

Good at protecting information and telecommunication since VPN facilitates secure and tunnelled access. Very accessible to the average consumer as well.

Components needed for a VPN

1. NAS (Network Access Server) - A server which authenticates user credentials before granting them access to the Internet.

2. Client software - This sets up the tunnelled connection and encryption between the user and NAS, providing the VPN’s security.

PAN (Personal Area Network)

Connection of devices and individuals (range of 10 metres). For example, a person travelling with a laptop, a portable printer, or anything wireless.

P2P (Peer-to-Peer)

“Peers” or devices that are connected to each other via the Internet. Files shared directly without a central server. Each device is both a server and client. LimeWire is an example of a P2P service, which are often used for piracy!

OSI Model

Model to detail how data is transmitted from one device to another over a network. Only 2 layers must be known for this exam.

Layer 1: Physical

Level of actual hardware. Defines the physical aspects of a network and voltage, timing, connections etc.

Layer 2: Data

The appropriate protocol is assigned to data in this layer. The type of network being used and packet sequencing (metadata) is also defined here.

Components of a Wireless Network

• Wireless router - uses radio waves to determine where packets go

• Wireless adapter - often built-in to a device so that they can communicate to a wireless network

• Extender - extends the range of the network by rebroadcasting its signal

• Router software - This configures the router, sets the unique SSID, and sets security parameters

Advantages of Wireless Networking

Deployment - initial setup of the network requires little more than a single access point.

Disadvantages of Wireless Networking

Security - Encryption technologies can combat most security issues, however, common users will not set up these precautions.

Encryption

The process of encoding data transmitted wirelessly between your device and router. Three main types are WEP, WPA, WPA2.

WPA (Wi-Fi Protected Access)

First implemented in 2003 to account for WEP/wired equivalent weaknesses.

WPA2

Replaced WPA, uses the AEP (Advanced Encryption Standard), a government grade encryption.

Authentication

Determining whether someone or something is what they say they are.

WPA2-PSK

Intended for home and very small office networks. Each wireless device is authenticated by the same 256-bit key. All users share a locally stored passphrase, which can be found and copied by anyone.

WPA2-ENT

Made for enterprises/business networks. Allows for more security than WPA2-PSK. WPA2-ENT creates new encryption keys each time users log on to the network with their unique passwords, and the passphrase to the network is not stored locally. It also allows for centralised control/management of user access.

MAC Address Filtering

A MAC address (Media Access Control address) is a unique identifier assigned to a device. MAC address filtering allows only machines with specific MAC addresses access to a network. You specify which addresses are allowed in the router software.

Disadvantages of MAC Address Filtering

A knowledgeable hacker can use software to scan for MAC Addresses currently accessing your network and then spoof their own MAC into a validated one.

Why is data compression necessary?

Data compression is the process of encoding data to take up less storage space and less bandwidth for transmission. Digital data are compressed by finding repeatable patterns of 0s and 1s. The more patterns found, the more data compressed. This allows for faster transmission speeds.

Latency

The amount of time required for data to travel between the sender and receiver. All computer networks experience some inherent latency.

Causes of lag/low latency

• Length of the route that the packets have to take between sender and receiver.

• Type of media transporting the data.(e.g. fiber optics, satellite, wireless, metal wiring)

• Network congestion - causes data to be retransmitted.

• Traffic load - how many people are using network.

• Time of day - people use network more during peak times.

• Weather - satellite and wireless signal interference

Protocols

Rules and conventions for communication over a network. HTTP, FTP, POP3, SMTP, IMAP, TCP are all examples of network protocols.

Why are protocols important?

Protocols assist in network communication and prevent issues like: data integrity, flow control, deadlock, congestion, and error checking.

Data Integrity

The overall completeness and accuracy of data. Must be imposed when transmitting data over a network. Error-checking and correction protocols control for this.

Flow Control

Utilised to manage the flow of data between two different network devices, which may have different levels of latency and sending/receiving capabilities. Flow control protocols are used to solve this.

Deadlock

This is a situation where two or more computers are waiting for the other to send data and therefore neither do. This may occur due to lost or corrupt signals. Protocols defining the order of communication are needed to prevent this.

Congestion

Network devices have a memory location called a buffer where received data is stored. When the buffer is full, more data cannot be received and stored. Congestion happens when more data is sent than the buffer can store. Data must be either kept or dropped. Protocols determine what to keep and what to drop. The TCP protocol is responsible for setting the policies for congestion that occurs with packets sent over the Internet

Error-checking

Data transmitted is subject to interference (noise) that can alter how the data is represented. Error-checking protocols exist to check these alterations and correct for them through redundancy, parity check/checking for single bit errors, and checksum methods.

Limitations of Data Compression

• Some compression methods (lossy) discard data - loss of quality during decompression

• The compressing/uncompressing process slows down the performance - bad when a file needs to be accessed quickly

• If you send compressed file to someone else via the Internet - the recipient may not have the software to open it