Topic 3: Networks Flashcards
Local area network (LAN)
A network that covers a local area.
- This usually includes a local office/building, thought they’re also somewhat common in homes now thanks to the spread of Wi-Fi.
Wide area network (WAN)
A network that covers a wider area than a LAN.
- Distances can range from a network connecting multiple buildings on a corporate or college campus to satellite links connecting offices in different countries.
Virtual local area network (VLAN)
A logical group of workstations, servers, and network devices that appear to be on the same LAN despite their geographical distribution. A VLAN allows a network of computers and users to communicate in a simulated environment as if they exist in a single LAN.
- VLANs are implemented to achieve scalability, and ease of network management.
Storage area network (SAN)
A secure high-speed data transfer network that provides access to consolidated block-level storage. A SAN makes a network of storage devices accessible to multiple servers.
Wireless local area network (WLAN)
A wireless distribution method for two or more devices that use high-frequency radio waves and often includes an access point to the internet.
- A WLAN allows users to move around the coverage area (often a home or small office) while maintaining a network connection.
- A WLAN is sometimes called a Wi-Fi network, but can include other transmission technologies.
Internet
A globally connected network (a network of networks) that uses the TCP/IP protocols to transmit data via various types of media.
Extranet
- A controlled private network that allows customers, partners, vendors, suppliers, and other businesses to gain information (typically about a specific company or educational institution) and do so without granting access to the organization’s entire network.
- An extranet is often a private part of a website. It is restricted to select users through user IDs, passwords, and other authentication mechanisms ion a login page.
Virtual private network (VPN)
Uses the internet to log into a network remotely and access its resources, but encrypts the connection to thwart eavesdroppers.
- If a company sets you up with a VPN, you can access your corporate intranet, file servers, or email from home or a coffee shop – just as if you were using it from your office.
Personal area network (PAN)
A network covering a very small area, usually a room.
- The best-known wireless PAN network technology is Bluetooth, and the most popular wired PAN is USB.
Peer-to-peet (P2P)
A network model in which files are exchanged.
- Some experts describe it as an “equal client” system where instead of accessing files from a server, the “peer” computers just swap them amongst each other.
Standards
The common ground on which hardware and software manufacturers can depend on to build systems that can communicate with each other. As such, they are thought to provide a common international “language” that enables compatibility for all computer systems throughout the globe.
OSI model layers
Application: Human-computer interaction layer, where applications can access the network services
Presentation: Ensures that data is in a usable format and is where data encryption occurs
Session: Maintains connections and is responsible for controlling ports and sections
Transport: Transmits data using transmission protocols including TCP and UDP
Network: Decides which physical path the data will take
Data Link: Defines the format of data on the network
Physical: Transmits raw bit stream over the physical medium
Fundamental VPN technologies
Encryption: The process of encoding data so that only a computer with the right decoder will be able to read and use it
Tunneling: Involves establishing and maintaining a logical network connection (that may contain intermediate hops). On this connection, packets constructed in a specific VPN protocol format are encapsulated within some other base or carrier protocol, then transmitted between VPN client and server, and finally de-encapsulated on the receiving side.
In a VPN, the computers at each end of the tunner encrypt the data entering the tunner and decrypt it at the other end.
Pros and cons of VPN
Pros:
- info can be accessed in remote places
- no need for long distance leased lines (therefore decreased cost)
- enhanced security through encryption
Cons:
- not all VPN products are compatible across different vendors
- reliability is not directly under the organization’s control
- needs a professional to ensure sufficient security and protection
Pro or Con: telecommuting
Data Packet
Define
A packet is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched
network.
Protocol
Define
International rules that ensure the transfer of data between systems. A protocol recognized as the standard for a certain type of transfer is called a standard protocol.
Functions of protocols / why protocols are necessary
- Data integrity: Ensures data is not changed or corrupted during transmission (i.e. ensures completeness, accuracy, and consistency of data)
- Flow control: The mechanism that ensures that the rate at which a sender is transmitting data is in proportion with the receiver’s receiving capacities
- Deadlock prevention: A deadlock is a situation where two or more programs are trying to use/access the same resource, thereby preventing each other from using it. It is then up to the relevant protocol to stop both, and re-queue them so that they can happen sequentially.
- Congestion control: Prevents requests on network resources from exceeding capacity
- Error checking: Refers to the techniques used to detect impairments introduced into dara while it is transmitted from source to destination
Factors affecting speed of data transmission
- Traffic: more traffic = slower data transfer speed
- Time of day: some times are busier than others
- Distance between source and destination: more distance = slower data transfer speed
- Bandwidth of network: bandwidth is the amount of data that can be transmitted over a certain period of time
Compression
define
encoding information to use fewer bits than the original data entity
Why is compression necessary?
When transmitting across a network it enables data to be disseminated more rapidly (smaller data size = more data that can be sent in the same amount of time)
What is packet switching?
The type of network in which relatively small units of data called packets are routed through a network based in the destination address contained within each packet. Routers take data packets along different paths through networks to the best next step closer to the destination address. Eventually the packet reaches the router that knows the address of the destination device. Packets assemble there.
Advantages of wireless networking
- Uses unlicensed radio spectrum: Doesn’t cost anything
- LANs can be set up without cabling: Doesn’t take space or time to lay the cables. No extra cost on cables
- WiFi can support roaming between access points: People can switch from router to router automatically depending in which connection is best
- Global standards (eg. 802.11n)
- Setup costs are minimal: Many types are available on the market and they are affordable
Disadvantages of wireless network
- Interference: as the 2.4GHz spectrum is often crowded with other devices
- Limited Range
- WEP: this encryption is not difficult to hack and WPA2 has solved this problem
- Access Points: these can be used to steal data
- Health Concerns (radiation)
Hardware components of wireless networks
- Node: PC, Laptop, Tablet, Printer
- Wireless network interface card
- Radio waves (Bluetooth/WiFi)
- Connection point: Wireless AP / Router
Software components of wireless networks
- Network Operating System (with drivers)
- Protocol stack (TCP/IP)
- Applications (Browser/File explorer)
Types of wireless networks
Wi-Fi (Wireless Fidelity):
- Also called Wireless LAN (WLAN)
- Used in laptops/mobile devices to connect wirelessly to home network
- Most preferred network type to implement a home network
- Allows relatively slow to fast data transmissions (depending on the version)
- Backwards compatible with most older Wi-Fi standards (a/b/g/n)
- Small transmitting radius makes it suited for homes, usually <20m
WiMAX (Worldwide Interoperability for Microwave Access):
- Designed for large distance high speed internet access
- Relatively cheap method of providing internet over a large area - suited for poorer countries
- Rivalled by Long Term Evolution (LTE) standard
- Can be used as a form of wireless variant of DSL phone transmission lines
3G (Third Generation):
- The primary way mobile phones access the internet today
- Allows the tunnelling of phone lines (mobiles don’t have to switch back to phone network when receiving a call
- Relatively fast
Future Networks:
- 5G
- Tactile internet
Network security methods
- encryption (symmetric-key & public-key)
- user ID
- trusted media access control (MAC)
- Firewall
Symmetric key encryption
definition + pros and cons
A device has a key to encrypt packets, and the receiving device has the same key to decrypt it.
Pros:
- faster than public-key
- uses less computer resources
Cons:
- keys must be shared before use
- danger of key becoming known by unauthorized individuals
Public key encryption
definition + pros and cons
Involves a public key for encryption and a private one for decryption, both mathematically linked.
Pros:
- two sides don’t need to share the secret key beforehand to communicate
Cons:
- messages take longer to encrypt and decrypt
- authenticity of public key needs to be verified
user ID
definition + pros and cons
Use of a password to access a device and/or a web interface that is used to set up wireless routers or access points.
Pros:
- easy to use
- prevents unauthorized access
Cons:
- entering a password each time may be time-consuming
- weak password is easy to crack
Trusted media access control (MAC)
definition + pros and cons
Every device in a network has a unique MAC address of 12 characters. Network permits access only to specified, trusted devices based on their MAC address. The MAC address of an untrusted device is blocked so it cannot connect to the network.
Pros:
* Extra security
Cons:
* danger of allowed list of MAC addresses beign discovered
* difficult to manage the list as it grows
firewall
definition + pros and cons
Can be either software installed on each device or router hardware that protects hackers accessing devices trhough wireless connection. Firewalls filter incoming traffic and can block some messages from coming through, as well as control/limit user’s own access to the internet.
Pros:
* software monitors traffic between device and network and prevents unauthorized access
* router hardware firewall prevents unauthorized people from accessing the network
Cons:
* may slow down the device
* issues about censorship with software firewall, depending on the org.
* router firewall can’t stop a person within a range of your Wi-Fi from getting onto your Wi-Fi network
characteristics of data packets
- contains a set amount of data
- fixed structure
- contains data that is to be sent via a communications channel
- contains specific details for transmission e.g. address of sender and receiver, error codes etc.
