Transcript of Core 3: Communication Systems. Internet The internet is a worldwide packet switched public network...
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- Core 3: Communication Systems
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- Internet The internet is a worldwide packet switched public
network based on the internet protocol where all data moves between
nodes within IP datagrams. The internet is designed for
asynchronous (emails etc) and synchronous (webcam etc)
purposes.
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- Public Switched Telephone Network (PSTN) PSTN is a network that
carried traditional telephone connections throughout the world. It
establishes a synchronous connection between individual clients in
a circuit. Internet service providers often lease out PSTN
connections rather than establish their own infrastructure.
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- Intranet and Extranet An intranet is a private network
maintained by a company or government organisation and is based on
the Internet protocol (IP). Optical fibres are often used in
intranets because the short distances arent too expensive to cover
with cables. WAN stands for private Wide Area Network. Extranets
are an extension of an intranet and allow customers and other users
outside the organisation. For this reason the extranet MUST be
secure. Both Intranets and Extranets can also include VPNs or
Virtual Private Networks. A VPN uses the internet to allow external
access to an organisations Intranet.
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- Teleconferencing is a multi-location, multi- person conference
where audio, video and/or other data is communicated in real time
to all participants. There are two examples of this from page 262
271 of the text.
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- For one of the two examples in the text create single page
document that includes the Information System diagram (see right)
as well as a list of advantages /disadvantages below the diagram.
This should fit on a single A4 page.
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- Distance Education System Environment ABC University, lecturer,
local students, servers for video transfer, remote students and
their PCs and internet connections. Purpose Enable remote students
equal learning opportunities, reduce work for lecturers, allow
remote students to connect via the IT they have in their home,
allow for minimal disruption within the lecture (webcam etc should
be used discretely).
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- Distance Education System Data/Information Participant audio,
Participant video stream, application software for running
conference or sharing documents during conference, text chat
program, IP addresses, PIN numbers. Participants Lecturers, local
students, remote students. IT Purpose built audio, video, web
teleconferencing room including PCs, displays, projectors, cameras,
microphones.
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- Distance Education System Information Processes Audio and video
are collected, audio and video are transferred through internet,
servers process, information is received and displayed.
Advantages/Disadvantages Remotes students do not need any special
IT, Video streams are automatically adjusted to fit remote students
internet specs, PTSN provides reliable audio connection for all
participants, remote students with poor internet connections may
experience video lag, home telephone of remote student may be tied
up during extensive telecom calls.
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- 1. Traditional Phone and Fax Telephones are largely similar to
the way that they were when first created 100 years ago. Old phones
used to use pulse dialling and were connected through copper wires
that were manually changed by an operator. Now phones use tone
dialling and the copper wire is changed using electronic switching,
which is automatic. There is also a use of analogue AND digital
transmission rather than analogue only. The PSTN includes more
digital mediums and less use of copper wire now.
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- 1. Traditional Phone and Fax Fax machines are similar to
telephones. These days they use a digital signal of compressed bits
to describe an image collected by light sensors. The receiver then
recreates the image and uses an inkjet or laser printer to
reproduce it.
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- 2. Voicemail and Phone Information Services Voice mail used to
be a timed analogue recording that was stored on a tape. Now it is
a digital version that records after having given the outgoing
message after a certain number of rings. The digital file is stored
in the customers voice mailbox. The customer can then ring the
voicemail and have the recording played back to them. Voice mail
can also be used as a decision tree; for example Press 1 to access
junior school. Press 2 to access the front office. Etc. Come to
page 279 of the text
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- 3. Voice over Internet Protocol (VoIP) Voice Over Internet
Protocol (VOIP) uses the internet to transfer individual digital
recordings that are strung together to sound like a conversation.
It uses IP addresses and the internet rather than PSTN. It is also
different because it provides an interface for the connection. Come
to page 283 284
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- 4. Electronic Mail During email the message is composed of two
broad components the envelope and the contents. Envelope: The
envelope contains the information required to transfer the message
to its destination, much like a physical envelope. The envelope
data is examined and used by SMTP servers to relay messages to
other SMTP servers and ultimately their destination.
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- 4. Electronic Mail Email Contents: The contents contains the
actual message data together with various header fields used to
specify sender, receiver, date/time, subject and also relationship
of this message to other related messages. Page 285 287 of the text
outlines all of the possible header fields attached in the contents
of an email.
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- 4. Electronic Mail MIME (Multipurpose Internet Mail Extensions
Mime is the protocol used to code non- textual data and attachments
into ASCII so that it can be transmitted within email messages.
MIME is used to code HTML email messages, image files, video files
and any other type of file attached and transmitted via email.
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- Financial transactions that occur over an electronic network
are all examples of electronic commerce. In this section we will
explore ATMs, EFTPOS and Internet Banking.
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- ATMs or Automatic Teller Machines ATMs are used to withdraw
money from a bank account. The collection devices include a
magnetic stripe reader that collects magnetic information from the
back of the customers card, and a keypad used to input the
customers PIN. Display includes an LCD screen and a receipt
printer. Cash dispensers include a safe that contains drawers for
each denomination of bank note and another drawer for bills that
are rejected. ATMs are connected to their respective bank using a
dedicated phone line or an Ethernet connection.
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- EFTPOS or Electronic Funds Transfer at point of sale EFTPOS
machines are similar to ATMs in that they use a card and PIN to
access a bank account and make a transfer. However, they are
different in that they can only charge money on an account rather
than withdraw money, also they dont deal with cash. They are
connected to the banks through a dedicated phone line on the PSTN.
EFTPOS organises the transfer of cash from one institute to another
by verifying the account and then making a withdrawal from the
bank, and a deposit in the receiving institute.
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- Internet Banking Internet banking allows bank customers to pay
bills, transfer money between accounts and perform carious other
functions from the comfort of their home or office. It is more cost
effective than face-to-face banking and is also available 24/7.
Uses user ID and password. Connects directly to the banks web
server using a URL with https. Https shows that it is a http with
SSL (secure sockets layer) or TLS (Transport Layer Security).
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- Come to page 300 of the text