Communication Flashcards
LAN
LAN - private network for a small geographic area. Has shared resources, it is scalable and many computers can be connected the LAN. A large LAN has a specialist server that carries out ONLY one role.
WAN
Multiple LANS come together to make up a WAN networks connected to other networks which can communicate over a wide geographic area. Like towns, regions and globally. Uses telephone wires and satellite communications
Client server model
at least one computer used to “serve” other computers are referred to as “clients” server provides services / applications etc. which may be requested by clients
Peer to peer networking
All computers are of equal status Each computer provides access to resources and data // data is distributed Computers can communicate and share resource Each computer is responsible for its own security
Thick clients
More extensive resources. Higher processing power, memory and data storage. Application software is installed locally.
Thin clients
Limited resources with limited processing power, memory and data storage. server does all the work, the role of the client is to only provide the server with input.
Bus topology
Each device is called a node, it has two terminators at the end to avoid bouncing of data. Data gets sent throughout the whole cable. Uses both twisted pair and coaxial cables.
Star topology
Each node has a connection to a central device. The data transmission can be unicast, multicast or broadcast. It uses a central device to connect to the clients or devices.
Mesh topology
Every node is connected to every node. Data transmission can be unicast, multicast or broadcast.
CLOUDDD
Accessing a service/files/software on a remote server
Public cloud
Computing services offered by 3rd party provider over the public
Internet open/available to anyone with the appropriate
equipment/software/credentials
Private cloud
Computing services offered either over the Internet or a private internal
network Only available to select users not the general public. Private is a dedicated/bespoke system only accessible for/from the
organization
Disadvantages of peer to peer
each computer is at risk from viruses from other computers
No central management of backup if the data from one computer is not backed up it is lost to all of them
No central management of files/software consistency may be difficult to maintain
In order to share files etc. all the computers involved need to be switched
on . may not be always available
Twisted pair copper cables
Cancels out electromagnetic interference
Made up of two insulated copper wires. Used in LAN lowest data transfer, cheapest. Shielded - commercially used. Unshielded - residency.
Coaxial cables
Used in bus networking for the ethernet. Electromagnetic interference from other metal objects will not affect the signals. Better data transfer, best jamming capacity.
Fibre-optic cables
Made of glass, best data transfer. small signal. High resistance. Single - Light faster good for telecommunications.
Hub
Connects devices from local area
takes any data packet sent to it and sends it to every computer
not secure
can be wired or wireless
Switch
Similar to hub
sends it to the correct device once more smarter
Repeaters
Boosts signals or enhances signals
to be used in a large distance
hubs that contains repeaters are known as repeating hubs. prevents dead spots - where wifi is not reached at a certain area
Bridge
Connects one LAN to another LAN that uses the same protocol. they are often use to connect different part of LAN to function as a single LAN to prevent traffic and flooding
Router
To receive packets from devices or the Internet
* To forward / route packets to the destination
* To find the destination of the packet
* To assign / allocate private IP addresses to devices on LAN
Ethernet
Type of bus networking, uses the MAC address of a device rather than the IP as devices can share the same IP addresses if they are connected to different networks
CSMA/CD
Ethernet uses Carrier Sense Multiple Access/Collision Detection (CSMA/CD)
A workstation / node (wishing to transmit) listens to the communication
channel data is only sent when the channel is free // … if channel is free data
is sent Because there is more than one computer connected to the same
transmission medium two workstations can start to transmit at the same time, causing a
collision If a collision happens, the workstations send a (jamming) signal / abort
transmission and each waits a random amount of time before attempting to resend
Bit streaming
sequence of digital signals / bits
– over a communication path Internet
– transfer of data at high speed
– requires fast broadband connection
– requires some form of buffering this makes stream run more smoothly
– bits arrive in the same order as sent
DNS
WWW is a collection of interlinked, hypertext documents/webpages/multimedia resources (accessed via the Internet) //WWW is content from web servers organized as
web pages
* Internet is the global connection of interconnected computer networks
* The Internet uses TCP/IP protocol / WWW uses http protocols to transmit data
Gateways
Routers can act as gateways but gateways cannot act like routers. Gateways cannot move packets. It is a device that helps you get connected to the internet.
It can connect two dissimilar protocols
Modems
Converts analogue signals to digital signals, inbuilt and cannot be seen. It is a part of the router now.
NIC
Receives analogue radio waves convert them to digital / binary
Checks incoming transmissions for correct MAC / IP address ignore transmissions not intended for it
Takes digital/binary input and converts to analogue waves sends the radio waves via the antenna
Encrypts / encodes the data
Decrypts / decodes the data
WNIC
Hardware component that allows a device to connect to
a wireless network // Provides a MAC address to the
device to identify it on the wireless network
WAP
Hardware component that provides radio
communication from the central device to nodes on the
network
IP v 4 Types
Network ID
Class A - Byte 1
Class B - Byte 1 and byte 2
Class C - Byte 1, byte 2 and byte 3
Host ID
Class A - Byte 2, byte 3 and byte 4
Class B - Byte 3 and byte 4
Class C - Byte 4
Public IP address
It is visible to any device on the internet
Private IP address
It is only visible to devices within the Local
Area Network (LAN)
Dynamic IP address
A new one is reallocated each time a device
connects to the internet
Static IP address
It does not change each time a device
connects to the internet
