Personal area network (PAN): This network is formed of mobile devices that are connected to allow them to communicate over a short distance, such as a mobile phone connected to a wireless headset.

Local area network (LAN): The network is confined to a small geographical area such as an office or home.

Wide area network (WAN): An example of a WAN is the Internet, where multiple networks are interconnected to allow the global exchange of data. In the context of an organisation, the WAN could be made up of distinct networks in different countries.

Workstations are also known as clients in a Windows or Linux based environment

Servers are used to provide centralised control and make network services available to client systems. Servers commonly have specialised operating systems installed to enable this functionality.

A host is any device such as a server, workstation or printer that is connected to a network to allow the exchange of data.

Peer-to-peer: In peer-to-peer (P2P) networking, a group of computers are linked together with equal permissions and responsibilities for processing data. This type of network is commonly used in small organisations and home networks of less than 10 computers to reduce the complexity of administration.

Client-server networks: Client-server networks are computer networks that use a dedicated computer (server) to store data, manage/provide resources and control user access. Client-server networks are designed to provide centralised administration to a large number of devices that are connected to a network.

The Internet is a global public network consisting of interconnected networks that provides information and communication services.

Intranet is a type of network that utilises internal networks within an organisation to provide a private, secured network to allow access to web based resources and information which are not publicly available.

An extranet is a private network designed to allow clients and external partner organisations to communicate and share information over a secure network. It often results from the need to allow clients to access to information or to interact with information contained on an Intranet.

Wireless topologies:
Ad-hoc mode - Devices connect without the use of a device such as a wireless router.
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Infrastructure mode - Devices connect to the network using a device such as a wireless router.
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Bus topology advantage: It works very efficient when used in a small network/Length of cable required is less than other topologies/Very cost-effective as compared to other topologies

Bus topology disadvantage: Additional devices slow the network down/If a main cable is damaged the whole network fails/This network topology is very slow as compared to other topologies

Star topology advantage: If one cable or device fails then all the others will still work/No disruptions to the network when connecting or removing devices/Easy fault detection because the link are often easily identified

Star topology disadvantage: More expensive than linear bus topology/Extra hardware is required/If hub goes down everything goes down

Ring topology advantage: Data flows in one direction which reduces the chance of packet collisions/Equal access to the resources/Easy to manage

Ring topology disadvantage: If one workstation shuts down, it affects whole network or if a node goes down entire network goes down/It is Expensive/Difficult to troubleshoot the ring.

Mesh topology advantage: Failure during a single device won't break the network/Fault identification is straightforward/It provides high privacy and security

Mesh topology disadvantage: It's costly as compared to the opposite network topologies/Maintenance needs are challenging with a mesh

Example:
Mr. Cooper wants to send Ms. Palmer an email. Mr. Cooper composes his message in an email application on his laptop and then hits ‘send’. His email application will pass his email message over to the application layer, which will pick a protocol (SMTP) and pass the data along to the presentation layer. The presentation layer will then compress the data and then it will hit the session layer, which will initialize the communication session.

The data will then hit the sender’s transportation layer where it will be segmented, then those segments will be broken up into packets at the network layer, which will be broken down even further into frames at the data link layer. The data link layer will then deliver those frames to the physical layer, which will convert the data into a bitstream of 1s and 0s and send it through a physical medium, such as a cable.

Once Ms. Palmer’s computer receives the bit stream through a physical medium (such as her wifi), the data will flow through the same series of layers on her device, but in the opposite order.

The IEEE is a professional association that is dedicated to advancing technology. As a part of this process they have a body that is responsible for setting and updating standards for multiple technologies such as networking. These standards are used to ensure that devices, media and software from different manufacturers are compatible.

RG-58 coaxial cable characteristics:

Cable type: Thinnet
Cable grade: RG-58
Cable thickness: 0.25in
Maximum distance: 185m
Data transfer rate: 10Mbps
Connector: BNC

RG-8 coaxial cable characteristics:

Cable type: Thicknet
Cable grade: RG-8
Cable thickness: 0.5in
Maximum distance: 500m
Data transfer rate: 10Mbps
Connector: AUI

UTP cabling consists of four pairs of wires that are encased in an outer sheaf, each of the pairs is twisted together to interference from adjacent wires.
.

STP cables have additional shielding added and would be used in an environment where there is significant electromagnetic interference (EMI) being generated by machinery.

Steps:

Cut the cable to the required length.

Use the wire stripper to remove about one inch of the cable sheaf from the end of the cable.

Separate and straighten out the wires, so they are no longer twisted.

Arrange the wires in the following order:
green/white
solid green
orange/white
solid blue
blue/white
orange
red/white
red.

Make sure the wires lay flat and parallel, with no spaces between them. Trim them evenly, leaving only half an inch sticking out from the uncut cable sheath.

Check that the wires are arranged in the correct colour order.

Hold the RJ-45 connector with the clip facing down and away from you. Push the wires into the plug.

Check that the wires are flat and even at the front of the plug so that they will make a good electrical connection.

Use the crimping tool to squeeze the plug, so the wires are held firmly in place.

Repeat the process with the other end of the cable.

Test the connections using a cable tester.

The two main types of fibre optic cable are single-mode fibre and multimode fibre. Single-mode fibre optic cables carry a single beam of light generated laser over distances up to 100km. Multimode fibre optic cables carry multiple beams of light over short distances. These beams of light can be generated using inexpensive sources such as LEDs
.

There are three main types of antenna used by wireless access points and routers:

Omnidirectional antennae transmit the signal in all directions and are used to provide cover over a wide area.

Semi-directional antennae transmit the signal in a single direction providing a strong long-range signal in the specified direction.

Highly directional antennae transmit a narrow-focused signal in a single direction and are used in point-to-point systems.

IEEE 802.11 standards:

The IEEE project standards 802.11 focus on the implementation of wireless local area networks (WLANs) and have evolved to incorporate technological improvements.

IEEE 802.15 standards:

The IEEE 802.15 standards are focused on the development and implementation of wireless personal area networks (PAN). For example, 802.15.1 defines the physical layer and media access control (MAC) standards for Bluetooth connectivity, whereas 802.15.6 deals with body area networks.

Threats to wireless networks

Data emanation: Network devices and computer systems emit data that can be collected and pieced together into readable data.

Interference: Interference from microwaves and other devices, such as mobile phones, can cause interference that disrupt wireless networks.

Packet sniffing: The data being transmitted on a wireless network can be intercepted using a device with a wireless connection and sniffer software. Hence the need for data encryption.

War driving occurs when individuals drive around an area with a laptop trying to locate wireless networks that are vulnerable and which they can connect to. To prevent this access points should be situated in the middle of the building and the power level should be configured to prevent the signal from radiating beyond the boundaries of the building.

War chalking - Once an individual undertaking war driving has identified a vulnerable network they will identify this network by chalking symbols on the wall of the building containing the network. These symbols identify the configuration of the network including the SSI and bandwidth available.

Rogue access points are unauthorised access points that have been added to the existing network infrastructure. Once the access point has been connected to the network it can be used to gain access to the network without the network administrator being aware. Hackers can install a rogue access point and configure it to appear as a valid access so that all of the data being transmitted across the network will be received by the device. This type of attack is known as an 'evil twin' attack.

Troubleshooting applications

Heat maps When troubleshooting wireless networks, applications can be used to generate heat maps which can be used to identify dead zones and improve network coverage.

Radio frequency (RF) surveying applications, such as NetSpot, are used to determine the feasibility of implementing a wireless network in a specific area and identifying the optimal placement of the access point. They can also be used to identify weak signals on a wireless network as part of the troubleshooting process.

Packet analysers are hardware or software capable of intercepting and logging data flow across a network.

Monitoring network performance

Various tools can be used to monitor networks to identify performance issues such as network congestion

Configuration management

Monitoring and reviewing system configuration aids in identifying where potential issues may occur, such as settings for a particular device being inadvertently changed.

Physical maintenance

The physical maintenance other networks include day-to-day activities such as cleaning monitors and keyboards. It could also involve conducting physical checks on the condition of cables to ensure that they still serviceable.

Antivirus software

Scheduling scans – allow the scheduling of scans to be undertaken at a time determined by the system administrator.

Definition updates – definitions are produced to provide the antivirus software with up to date information of all known viruses. Therefore, these should be updated on a regular basis

Protocol analysers

Protocol analysers can be either hardware or software tools that are used to capture and analyse data that is flowing across the network. Wireshark, is an example of a free open-source packet analyser.

TCPdump is another example of a packet analyser. Unlike Wireshark it is a CLI utility that is predominately used with Linux based OSs.

The ScanDisk utility is used to check hard disks for errors and to repair them. (Windows)

MemTest is a utility designed to place RAM under strain and assess if it can reliably store data. If the system fails the test, it could be due to old or damaged hardware. The Linux equivalent to MemTest is vmstat.

The TOP command allows users to view the active processes and monitor the usage of system resource usage in a Linux environment

The motherboard is the main printed circuit board to which all components and external peripherals connect.

When the system boots, the instructions contained in the basic input/output systems (BIOS) are loaded into the system. These instructions inform the processor where the operating system is located and how to load it into RAM.

Complementary metal-oxide semiconductor (CMOS) - The CMOS is a small piece of volatile memory that stores the information required by the BIOS. There is a small battery included on the motherboard that is used to supply power to the CMOS when the system is powered down.

The computer's central processing unit (CPU) is the portion of a computer that retrieves and executes instructions.

RAM is volatile memory that is used to store the data and code that is required by a running application. Without the need to access slower permanent storage such as the hard drive.

Cache memory is a volatile memory type that is commonly mounted on the CPU package and stores frequently used instructions and data. This reduces the need to access the slower RAM to fetch frequently used instructions and data, thus speeding up the process.

A hard disk drive (HDD) is a non-volatile computer storage device containing magnetic disks or platters rotating at high speeds. It is a secondary storage device used to store data permanently

SSD - Unlike hard drives, SSDs do not have any moving parts. They store the data using flash memory. This results in a faster data transfer rate than those achieved by hard drives, however they are a lot more expensive than conventional hard drives.

RAID 10 mirroring stripe

RAID 10 is implemented as a striped array whose segments are then mirrored. Under certain circumstances, RAID 10 array can sustain multiple simultaneous drive failures.

A proprietary operating system (OS) is typically owned by the individual or organisation that developed it. This type of OS often has specific licensing terms that limit its usage. For instance, Apple limit the use of their MAC OS X to their devices only.

As the source code remains the intellectual property of the developer, it is usually kept secret and end users are charged a fee to use the operating system.

The developers of open-source operating systems make the source code freely available with a licence that allows individuals and organisations to study, change and distribute the software to anyone and for any purpose.

Domain controller

In a Windows based network, a domain controller is the server that is responsible for responding to authentication requests. This is normally achieved by implementing Active Directory, which stores information regarding objects such as users and their authentication details.

Email Server

Microsoft Exchange is an example of software that can be installed on a Windows based OS to facilitate the provision of email services. There are three main protocols associated with the transmission of emails:

Simple Mail Transfer Protocol (SMTP) – SMTP is used to send email messages between servers.

Post Office Protocol (POP) – By default POP is configured to download all new messages from the email server on to the device once a connection is established. Once they have been downloaded onto the device, they are then deleted. As the emails are stored on the device and not the server they will not be available if another device is used at a later date.

Internet Message Access Protocol (IMAP) – Unlike POP, IMAP stores emails on the server allowing access to emails from multiple devices. The emails will be available until they are deleted from the server.

File server

File servers can be dedicated systems or network storage architecture devices that are configured to allow users to store and share files.

Domain name system (DNS) server

A DNS server translates the domain name into an IP address. DNS works like a phone book, by managing the mapping between names and numbers. DNS servers translate requests for domain names into IP addresses.

Dynamic Host Configuration Protocol (DHCP) server

DHCP uses a server to automate the process of issuing IP addresses. The DHCP server contains a range of IP addresses known as a scope. When a request for an IP address is received from a computer, the DHCP server will select an IP address from its scope that is not already leased to another device and offer it to the computer making the request. The computer then accepts the offer and the DHCP sever will then send the IP information and confirm the lease of the IP address.

Proxy server

A proxy server is a device that is configured to act as an intermediary for requests for clients seeking resources from other servers.

FTP server

File Transfer Protocol servers are used to control the process of transmitting files between devices in different locations. Dependent on the size of the file you may be able to share it using email, however for large files this may not be possible, and this is where FTP can be used.

Firewalls

Firewalls can be implemented using either hardware or software solutions and are designed to prevent access to or from a network. They use a predetermined set of rules to control the flow of data into and from a network.

Stateless firewalls monitor network traffic and make decisions on whether to block packets based on static values such as source and destination addresses. Stateless firewalls are used to enhance security through the use of packet filtering. Packet filtering inspects incoming or outgoing packets and compares them against predefined criteria and will block or allow access based on the results.
Stateful firewalls are aware of communication paths and can monitor traffic from end to end. They can be configured to distinguish legitimate packets from different types of connections. When a packet is received it initialises communications. The packet is inspected and if it matches an existing firewall rule it is allowed to access the network and an entry is added to the state table. From this point forward, the packets in this particular communication session are allowed as they match an existing state table entry.

A bit (b) is the smallest unit used in computing it can be represented by a 1 or 0.
A byte (B) is a group of eight bits.
A kilobyte (KB) is a group of 1,024 bytes.
A megabyte (MB) is a group of 1,024 kilobytes
A gigabyte (GB) is a group of 1,024 megabytes.
A terabyte (TB) is a group of 1,024 gigabytes.
A petabyte (PB) is a group of 1,024 terabytes.
An exabyte (EB) is a group of 1,024 petrobytes.

IP address – at present there are two versions of Internet Protocol (IP) in use:

IP version 4 (IPv4) has 32 bits split into four octets and is expressed as a dotted decimal representation such as 192.168.5.21.
IPv6 addresses use 128 bit and are expressed as a hexadecimal value, separated by colons. An example IPv6 address is: 3ffe:1900:4545:3:200:f8ff:fe21:67cf.

Automatic Private IP Addressing (APIPA) is a Windows function that provides a DHCP auto-configuration addressing when the DHCP server is unavailable.

A subnet mask is a 32-bit number that masks an IP address and divides the IP address into a network address and host address. A subnet mask is made by setting network bits to all 1s and setting host bits to all 0s.

A default gateway serves as an access point used to send information to a device in another network or the Internet. Default simply means that this gateway is used by default unless an application specifies another gateway.

Preferred and alternate DNS. The preferred DNS is a specified primary choice to handle IP mapping. If the preferred choice times out after a time limit defined by an operating system, it will then attempt to try the alternate DNS.

Multilayer switches

Multilayer switches are often referred to as layer three switches. They are capable of using MAC addresses to perform filtering of traffic intended for the local network or, if configured, IP addresses to route data between networks.

Remote assistant allows users to send an invite to an individual so that they can access their device remotely. Once the connection has been established, the individual accessing the device remotely must provide a password that has been provided in the invitation, and the user must manually accept the connection. Remote assisstant allows limited control over the device.

Remote desktop allows administration of a device remotely as it allows full control over the system. To logon to the remote device, the administrator must enter the correct logon details for an account associated with the device being accessed. To allow this type of connection, the device must be configured to accept remote connections.

Virtual Network Computing utilises software that enables you to have a virtual desktop (server) on a remote computer. This virtual desktop can then be accessed using various client interfaces and browsers, providing access to a virtual desktop from a remote location.

Telnet is an abbreviation for 'terminal network' which is a protocol that is used to provide a bidirectional interactive text-based communication facility using a virtual terminal connection. Telnet can be used to access switches and routers, and to issue commands remotely.

A major weakness of Telnet is that the data transfer between the devices is not secured, therefore any user names and passwords used to gain access to the remote system are sent in plain text. To address these major issues, SSH is commonly used where a secure connection is essential.

PowerShell is a Microsoft utility which is built on the .NET framework. It provides a task-based command line shell and scripting language. These features are designed to allow system administrators and power users to automate the administration of operating systems and the processes related to the applications installed.