Topic 3: Networks Flashcards
LAN
Computer network that interconnects computers within a limited geographical area such as a building or a school.
PAN
Computer network for interconnecting electronic devices centered on an individual person’s workspace. Bluetooth for example. Can be wired or wireless.
WLAN and pros/cons
Wireless LAN
- Free movement
- Less expensive
- Less secure
WAN
Network that extends over a large geographic area for the primary purpose of computer networking. The best example is the Internet.
- Wired with fiber optic
- Wireless by microwaves or satellite transmissions
Extranet
Computer network that uses the Internet to allow controlled access by specific users to a specific LAN or WAN.
It can be used by an enterprise to secure part of its network and allow people from outside of the company to access to some data.
Intranet
Collection of private computer networks within a company, school, or organization.
- It uses the TCP/IP protocol.
- It main purpose is to facilitate the communication between individuals or work groups, and improve data sharing.
SAN
Network created so that large storage devices can be accessible from servers in a convenient and easy way.
- Secure high speed data transfer network
- SAN can be accessed from multiple servers
Importance of standards
Without standards, manufacturers of networking products have no common ground on which to build their systems.
Makes communication easier
Hub
Connection point for devices on a single network, which consists of sevral ports.
- Network devices and computer systems connect to a hub with a wire to a port.
- The data sent to a hub is copied and sent to all the other devices attached to it.
- The device that is expecting the data receives it, and the others just ignore the entering data.
- This slows down a network.
P2P
Distributed network where all the computer systems in the networks are both clients and servers at the same time.
Layers of OSI model
Physical (physical communication) Data Link Network Transport Session presentation Application (virtual communication)
VPN
Technology that creates a safe and encrypted connection over a less secure network, such as the internet.
Server
Can either be a computer system or a software app that provides a service to other computer systems connected to the same network.
Client
Can either be a computer system or a software app that requests a service from a server connected to the same network.
Protocol
Set of rules for data communication over a network to enable 2 or more devices understand eachother.
Used so that both sender and receiver are using/expecting the same formats/methods, to allow data to be transmitted successfully / without errors;
Protocol functions
Data integrity: Ensures that information has not been changed or corrupted.
Source integrity: Sender identity validated
Flow control: It ensures at which rate a node can transfer information in relation with the capability of other node to receive that information.
Congestion management: Modern networks avoids this collapses with some specifics applications.
Deadlock prevention: The protocol needs to stop both and requeue them so that they can happen sequentially.
Error Checking: Techniques used to detect noise or other impairments, while transmitting from the source to the destination. F.e. Parity bit
Deadlock
The situation where two nodes processes are trying to access the same node at the same time. This cause that neither of them can be processed.
Congestion
State where a network node or link is carrying more data than it can handle. This can cause:
- Deterioration of server quality
- Queuing delay
- Frame or data packet loss
- Blocking of new connections.
Data packet
Portion of a message that is transmitted through a network. Contains data such as check digits and destination address.
- Contains a set amount of data;
- Contains a fixed structure: Header, Data, Trailer
- Contains data that is to be sent via a communications channel;
- Contains specific details for transmission.
Parts of a data packet
Header: Contains instructions about the data carried by the packet (length, packet number, destination, protocol, origin…)
Payload/Data/Body: Actual data that the packet is delivering to the destination.
If a packet is fixed-length, then the payload may be padded with blank information to make it the right size
Footer/Trailer: Contains a couple of bits that tell the receiving device that it has reached the end of the packet. It may also have some type of error checking.
What can affect transfer speed?
- Traffic: The more network traffic, the slower the data transfer on a particular connection will be
- Time of the day
- Distance
- Infrastructures
- Environmental issues (tempreature, etc)
- Data types transmitted (large files, streaming data…)
Bandwidth
Maximum rate of data transfer across a given path.
Throughput
The amount of data that can be sent and received within a specific timeframe.
Bottleneck
Occurs when the capacity of an application or a computer system is limited by a single component
Goodput
The application-level throughput of a communication
The number of useful information bits delivered by the network to a certain destination per unit of time.
Data compression types
Lossy and Lossless
Lossy compression
Lossy compression permanently removes bits of data that are redundant, insignificant or unnoticeable. A file does not restore in its original form.
Suitable with graphics, audio, video and images, where the deletion of some data bits has little or no apparent effect on the illustration of the content.
Data’s quality is compromised. IRREVERSABLE
Lossless compression
Allows the potential for a file to return to its original size, without the loss of a single bit of data, when the file is uncompressed. A file can be restored in its original form.
Suitable with text, images, sound. Data’s quality is no compromised. REVERSABLE
Packet Switching
Method of grouping data that is transmitted over a digital network into packets.
Characteristics of media
Security
Reliability
Cost
Speed
Advantages of wireless networking
- It’s free (Uses unlicensed radio spectrum)
- Doesn’t take space or time to lay the cables and no extra cost on cable (LANs don’t need cabling)
- Global standards
- People can switch from router to router automatically depending in which connection is best (WiFi acn support roaming between access points)
- Setup costs are minimal (many and affordable types in the market)
Disadvantages of wireless networking
- Interferences (spectrum is often crowded with other devices)
- Limited range
- Easy to hack (WEP inscription)
- Health concerns
Hardware components of wireless networking
- Node: PC, Laptop, Tablet, Printer
- Wireless network interface card
- Radio waves (Bluetooth/WiFi)
- Connection point: Wireless AP / Router
Software components of wireless networking
- Network Operating System (with drivers)
- Protocol stack (TCP/IP)
- Applications (Browser/File explorer)
Types of wireless networks
- WiFi
- Wimax
- Lte
- 3G
WIFI
• 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
• 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
- The primary way mobile phones access the internet today.
- Third generation of wireless mobile telecommunications technology
- Provides the ability to transfer voice and non-voice data, such as downloading programs, exchanging e-mails, and instant messaging.
Wireless Networks security methods
Authentication Encryption Firewalls MAC address control Physical security Antivirus Disable SSID broadcast (security through obscurity)
NIC
Network Interface card/controller is a computer hardware component that connects a computer to a computer network.
VPN
When you connect to a VPN, it creates an encrypted tunnel that secures data travelling between you and the VPN server. To secure each data packet, the VPN wraps each data packet with an outer packet whish is encrypted through encapsulation.
In this way, it encrypts your internet traffic and hides your IP and virtual location. Thaks to its encryption, 3rd parties cannot spy on your online activity or access that data.
