Flashcards in Chapter 2 - Communication and Internet technologies Deck (21)
What is simplex data transmission?
data transmission in one direction only
What is half-duplex data transmission?
data transmission in two directions but not at the same time
What is full-duplex data transmission?
data transmission in two directions at the same time
What is serial transmission?
data sent one bit at a time over a singe wire or channel
What is parallel transmission?
several bits of data sent down several wires/channels at the same time
What is asynchronous transmission?
data being transmitted in an agreed bit pattern
What is synchronous transmission?
a continuous stream of data which is accompanied by timing signals generated by an internal clock
What is a Universal serial bus? (USB)
an asynchronous serial data transmission method which has become an industry standard
What are the advantages of a USB?
the device is automatically detected
can only be entered one way around (prevents false connections)
device drivers are automatically loaded
What are parity checks?
Allows us to see if any bits have been skewed in data transmission
can either be odd or even number of 1's (parity complete with parity bit)
What are Automatic repeat request (ARQ)?
Uses an acknowledgement to indicate data is received correctly
A timeout is used which is the time allowed to elapse before an acknowledgement is received
What is checksum?
an additional value known as checksum is sent at teh end of the block of data
the checksum is based on the number of bytes in the block
if the checksum does not match on the receivers end, then an error has occoured
What is an echo check?
the data is returned to the sender
the sender then compares the data received with the data sent
if they are different then an error in data transmission has occoured
What is the issue with echo checks?
the data could become skewed when transferred back and not have been affected when sent to the receiver
What is an ISP?
a company that provides the user with access to the internet - usually with a monthly fee
gives a user an account and email address
What is an IP address?
an address which each device is given when connecting to the internet - will be different each time the device connects
What is a MAC address?
uniquely idenitifies a devic connected to the internet - the MAC address does not change but can be LAA or UAA
What is structure in HTML?
an essential part of HTML documents: includes semantics and structural mark ups of the documents
What is presentation in HTML?
the style of the document: how the document will appear on a user's computer screen
What is http?
a set of rules which must be obeyed when transferring files over the internet