1.3.3 - Networks Flashcards
What is a protocol?
A set of rules to control and govern communication between devices on a network.
What is a network
Two or more devices that are interconnected and can communicate with each other.
What is a standard
A set of hardware and software specifications that allow manufacturers to create products and services that are compatible with each other.
What is an IP Address?
A numerical address made of 4 numbers each between 0 and 255 that uniquely identifies a device on a network.
What is a MAC address
‘Media Access Control’ addresses
which are unique to a device that are used to identify each device on the network.
Explain how the Domain Name System (DNS) plays a role in websites being loaded.
- DNS is used to resolve IP corresponding to URL
- Request sent to DNS resolver.
- Resolver checks its cache and if it doesn’t hold the URL, it passes it in to the TLD Name server which checks its cache and returns the answer or passes it on to the Authoritative Name Server.
- The IP address is returned back up to the requesting client Or an error if no resolution can be found.
What is a LAN?
‘Local Area Network’- A group of devices connected over a small geographical area. The infrastructure is usually owned by the network owner.
What is a WAN?
‘Wide Area Network’ - Collection of connected computers/devices over a large geographical area often using 3rd party communications channels
What is more secure LAN or WAN
LAN
What is the structure of a data packet
- Header: Sender’s/transmitting IP address, Receiver’s/destination IP address, Protocol, Packet number and order, i.e. the place of the packet in the complete message.
- Payload: The actual data file to be transmitted.
- Trailer: End of packet marker, Error correcting code
Explain what is meant by packet switching
- Data is split into chunks called packets which have labels including address being sent to and the order its arranged into.
- Each packet is sent on the most convenient route meaning they may arrive in a different order to which they were sent.
- Once packets arrive at receiver they are reordered.
Explain what is meant by circuit switching
- Physically connects devices together
- Devices remain connected for the duration of data transmission.
- Establishes a route before transmission between the two computers for the duration of the message.
- Sends all packets on the same reserved route down the circuit in order.
- Packets remain in correct order but must be reassembled at the destination.
Firewalls
A computer application used in a network to prevent external users gaining unauthorised access to a computer system.
Proxies.
A computer application that has accesses to data on a different computer system or network. It controls the access of unauthorised. users to data and allows the operation of the system to be isolated from control by external users.
Encryption
The process of making data in a computer system unintelligible.
TCP/IP Stack
Transmission Control Protocol / Internet Protocol:
The most common general-purpose standard protocol that allows any networked computers (including those on the internet) to communicate with each other no matter their equipment.
Protocol Layering
The concept of a protocol not simply being a set of rules, but those rules being built up into very specific layers and those rule layers behind build on top of each other in a deliberate order creating a layered protocol stack. This results in the rules of a protocol being executed in a specific sequence as you move through the protocol stack.
DNS
Domain Name System
- DNS is used to resolve IP corresponding to URL
- Request sent to DNS resolver.
Resolver checks its cache and if it doesn’t hold the URL, it passes it in to the TLD Name server which checks its cache and returns the answer or passes on to the Authoritative Name Server
- The IP address is returned back up to the requesting client or an error if no resolution can be found
2 Types of Network Topology + Examples
- Physical - The physical layout of wires and components that form a network. E.g. Bus, Star, Mesh
- Logical - The layout which shows how data flows. E.g. LAN and WAN
Physical Bus Topology (Hint - ABB Bus)
All the terminals (devices) are connected to a backbone cable, the ends of which are plugged into a terminator
Advantages of Bus Topology
- Relatively inexpensive to set up
- Doesn’t require any additional
hardware
Disadvantages of Bus Topology
- If backbone cable fails, the entire
network gets disconnected - As traffic increases, performance
decreases - All computers can see the data
transmission
Physical Star Topology
- Star topologies use a central node, often a switch, to direct data through the network.
- MAC addresses are used to identify each device on the network.
Advantages of Star Topology
- Performance is consistent even with
heavy network traffic - If one cable fails, only that single
terminal is affected - Transmits data faster, giving better
performance than bus topology - Easy to add new stations.
- No data collisions
Disadvantages of Star Topology
- Expensive due to switch and cabling
- If the central switch fails, the rest of
the network fails
Physical Mesh Topology
Disadvantages of Star Topology
Advantages of Mesh Topology
- If using a wireless network, there is
no cabling cost - As the number of nodes increase,
the reliability and speed of network
becomes better - Nodes are automatically
incorporated - Nodes don’t go through a central
switch, improving speed
Disadvantages of Mesh Topology
- If using a wireless network, devices
with wireless capability (which
increases cost) must be purchased - If using a wired network, a large
quantity of cable is required
compared to other network
topologies like bus and star. This is
expensive. - Maintaining the network is difficult
Client Server
Terminals known as clients connected to a server. The server is a powerful, central computer. The server holds all of the important information and resources and has greater processing power than the terminals. Clients can request to use the server.
Advantages of Client-Server
- More secure as data is stored in one
location - Central backups are carried out so
there is no need for individual
backups - Data and resources can be shared
between clients
Disadvantages of Client-Server
- Relatively expensive to set up
- Functionality of terminals depends on the server; if this fails, performance falls
- Trained staff are required to maintain the server
Peer to Peer Server
- A network in which computers are connected to each other so that they can share files.
- Each device effectively acts as both a server and client, as it can both provide and request
resources. - Peer-to-peer networks are used in piracy, since it’s almost impossible to trace
the origin of files.
Advantages of Peer-to-peer
- Cheaper to set up
- Allows users to share resources
- Easy to maintain
- Not dependent on a central server
- Specialist staff are not required
Disadvantages of Peer-to-peer
- Impossible to trace the origin of files
- Backups must be performed
separately - Poorer security
- May be difficult to locate resources
