Chapter 2: Communications Flashcards
What is the role of a router in a network
- Connects two (or more) networks
- Can connect a network to a WAN // acts as the single access point
for - Receives packets and forwards towards the destination
- using the IP address of the destination
- Assigns private IP addresses
- Operates between similar networks // networks using the same protocol
- Can be used to segment a network
What is the difference between the internet and the World Wide Web
Internet
* massive network of networks/interconnected network of computer devices
- Internet stands for Interconnected Networks
- uses TCP/IP protocol
World Wide Web (www)
* is a collection of (multimedia) web pages/documents
- …stored on websites
- http/protocols used to transmit data
- web pages are written in HTML
- URLs specify the location of the web pages
- web documents are accessed using browsers
What is the role of a gateway in a network
- Connect two (or more) networks
- Can connect a network to a WAN // acts as the single access point
for - Receives packets and send packets towards the destination
- using the IP address of the destination
- Assigns private IP addresses
- Connects two dissimilar networks // networks that use different
protocols
How is a URL used to locate a resource on the WWW and how does a DNS help
- URL is a reference address to a resource on the Internet.
- The URL is passed to the nearest Domain Name Server (by browser software).
- DNS server stores a database / list of URLs and matching IP addresses.
- DNS (Name Resolver) looks for the URL in its database.
- Finds the matching IP address and returns it to the originator.
- Or if it cannot find it, it forwards to another Domain Name Server at a higher level.
What are the differences between a public and a private IP address
- Public address can be reached across the Internet.
- Private address can only be reached internally/through the LAN/Intranet // private address cannot be reached across the Internet.
- NAT (Network Address Translation) is necessary for a private IP address to access the Internet directly.
- A private address is more secure than a public address // A public address is less secure than a private address.
- Public addresses are provided by ISP / assigned by InterNIC // Private addresses are assigned by the router (of the network concerned).
- Public addresses are unique (to the Internet) // Private addresses (are unique within their network, but) can be duplicated within other (discrete) networks.
Describe the transmission of data using a PSTN.
The PSTN consists of many different types of communication lines
Data is transmitted in both directions at the same time // (full) duplex
data transmission
The communication passes through different switching centres
Benefits of the client server model
– files and resources are centralised
– creation of security / manage security
– user needs user name and password to access network
– centralised back-up
– intranet capability
– Internet monitoring
– clients can be less powerful machines, therefore less expensive to buy
– saving resources on server reduces the burden on the client
Describe the 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
What is the difference between real-time and on-demand bit streaming
- Real-time - a live stream of an event that is currently taking place
- On-demand - streaming of an event/programme that has taken place in the past
- Real time – the event is captured live with a video camera connected to a computer
- On-demand – Existing media are encoded to bit streaming format and uploaded to a server
- Real-time – cannot be paused / rewound etc
- On-demand – can be paused / re-wound / fast forwarded etc
Drawbacks of fibre optic cable over copper
- (Initial) installation cost is higher // Cable / hardware is more expensive
to buy (per metre) - Specialists / trained personnel needed to install / maintain
- Difficult to terminate // Electronics at both ends are more complex
- Fibre-optic cables can break when bent
- Only transmits data in one direction
- If a fibre-optic cable connection fails, many more services can be
affected
Benefits of fibre optic over copper cable
Less interference in signal
Signal does not degrade as fast // Needs less signal boosting
More difficult to hack // more secure
Greater bandwidth // Faster transmission speeds possible
How is data sent via bit streaming
- The data is compressed before transmitting
- The video is transmitted continuously as a series of bits
- The video is hosted on a media server
- On download, the server sends the data to a buffer on the client computers //
The buffer stores the data from the server - The recipient / user’s software receives bit stream from the buffer
What are the differences between IPv4 and IPv6
IPv4:
32 bit address split by “.”
Each block has vale between 0 to 255
Eg :255.0.1.255
IPv6:
128 bit address divided into eight 16 bit blocks by “:”
Each block could have 4 hex value ranging from 0000 to FFFF
Why is subnetting used in a network
To improve the security of the LAN
* … so that devices do not receive unintended data
To make the network management easier
* … because faults can be isolated more efficiently
To make the network easier to expand // For better control of network
growth
* … by allowing for greater range of IP addresses to be available
To improve network performance
What does CSMA/CD do
To monitor the communications channel
- To send data only when there is no data being transmitted / the line is
quiet / idle - To detect a collision and then stop transmissions of further data //
transmit a jamming signal
* To calculate a random wait time / back-off time
