Communication and Information Systems Ch 18

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Communication and Information Systems Ch 18
This chapter deals with how organisations

• use networks to improve communication and
  productivity within an organisation.
• how networks allow communication between
  organisations.

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Four ways in which a company can use its computer
network to support the exchange of data and
information

• Intranet so that communication can be delivered
  to the workstation so potentially everybody gets
  information at same time
• E-mail so that communication can be delivered to
  specific staff within the organisation
• Video-conferencing so that meetings can be
  arranged without the need for travel
• Collaborative software Ability to work on the
  same document so that workers in different areas
  of the company can collaborate

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Five more ways networks are used

• Electronic Data Interchange (EDI) allows one
  organisation to transfer data electronically to
  another organisation without the need for paper
  transactions
• A retail organisation can use point of sale (POS)
  terminals with electronic fund transfer (EFT)
  that transfers money from one bank account to
  another
• A network allows stock control to be managed
  interactively by decreasing the stock by one when
  an item is sold so that the other computers on
  the network can see up-to-date stock levels
• Telecommunting allows personnel to work at home
  reducing office overheads and absence.
• A centralised database allows all areas of the
  organisation to have access to the same data at
  the same time.

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Useful Definitions
NB Recap ICT2 Networks
A network may be a mixture of LANs and
WANs Public WANs such as the Internet can be
accessed by anyone for free or with the payment
of a fee Private networks have restricted access
eg only accessed by employees of a company A File
Server is a powerful computer with a large hard
disc. Data is stored here and can be accessed
from any terminal. A Printer Server is a
powerful computer that manages the allocation of
the printer to different jobs sent from different
workstations and maintains a queue of waiting
jobs. It may need to manage several printers in
different locations. A web server is a
powerful computer that hosts (stores) web sites
and organises the web pages on the site. The
server has the ability to restrict access to
those sites for unauthorised web users and allow
access to the stored web pages for authorised
users.. A Bridge is a piece of hardware that
physically connects a LAN to another network.
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Useful Definitions of LAN and WAN
LAN a collection of computers and peripherals
that are normally connected in one building or
site. They are connected via private cables or
private wireless links.
WAN a collection of computers spread over a
wide geographical area. They are connected
together via many different telecommunication
links such as microwave and satellite links. At
least one link is public.

• The WWW (world wide web) is a collection of
  information held on the internet in multimedia
  form. It is a network of networks!

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The Internet Infrastructure
Router

• The major physical pathways in a WAN are called
  the backbone and are high speed telecommunication
  links such as optical fibre. However many
  different telecommunication methods are used.
• The internet requires a set of protocols such as
  http that are conformed to by all such as the
  standards for technical detail (See Ch 23)
• Each computer on the internet is uniquely
  identified with a unique IP (Internet Protocol)
  address. Eg 192.168.0.233. This is then converted
  into a domain name which is easier to remember.
  You have to apply for a domain name.
• The domain name can be typed into a web browsers
  address line to view their web pages

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IP Addresses ? Domain names ? URL address
Router
DNS

• Once allocated, domain names are stored using the
  Domain Name System (DNS), a way of locating and
  translating domain names into the IP address of
  the computer containing the required website.
• www.ucas.ac.uk is a domain name. www says it is a
  website. Ucas is the organisations name. ac is an
  academic institution. Uk is the country where
  registered
• The uniform resource locator (URL) is a unique
  webpage identifier consisting of 3 parts
• The protocol generally http
• The domain name translated into the IP address
• The path and filename of the specific web page eg
  index/index.html
• Eg http//www.ucas.ac.uk/index/index.html

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Sending Data over the Internet Infrastructure

• Sent in small packets of data containing a
  destination address and sender address. A message
  can be broken up into many small packets
• Routers (hardware) act as gateways between
  networks and they maintain a table of available
  routes to other networks. They receive the
  packets, check their address and send them off in
  the right direction. The packet may pass through
  several routers before it gets to the destination
  computer. The router also checks the parity of
  the data to ensure the data is not corrupt. If
  corrupt the router will ask for the data packet
  to be sent again.
• The packets are reassembled on the destination
  computer into the correct order.

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The Internet Infrastructure

• If a home user with a standalone computer wants
  to connect to the internet they need
• ISP (Internet Service Provider)
• Telephone line modem OR Broadband fibre optic
  cable
• When the user requests information from the
  Internet it is sent to the unique IP address of
  the ISP. The users computer downloads it from
  there.
• Generally organisations have their own permanent
  connection to the Internet and so have to apply
  for their own domain name.

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Question about how the WWW works!

• In order to acquire a software update, the
  software manufacturers website is visited. When
  the link leading to the download area of the
  website is followed, the address becomes
• http//192.168.0.233/downloads/software.htm.
• (i) What does the http part of the address
  represent?(1m)
• (ii) 192.168.0.233 is an Internet address.
• Explain why Internet addresses are important for
  the correct functioning of the Internet.(2m)

Answer i) Http is the protocol being used
(1) ii) The address needs to be unique so that
only one machine is identified (1) as if more
than one machine has the same address, data
cannot be routed towards it (1)
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Distributed Databases

• A distributed database is a collection of
  different interrelated databases scattered over a
  network. Eg A hotel chain might use it to store
  details of reservations. Each hotel stores its
  own reservations on a local computer. Because all
  the hotel computers are networked together hotel
  staff can see the reservations from different
  hotels.
• Advantage
• Data that is used locally can be stored locally,
  network traffic is kept to a minimum
• Disadvantage
• As all data is not stored in one location , if
  one workstation was to fail with inadequate
  backup, other locations may suffer a loss of data
  
• Distributed system system where processing is
  carried out by sharing tasks between physically
  separate computers on a network.
• Distributed control local branches can access
  their data at any time and process it according
  to their priorities

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Distributed Databases Question

• A small reprographics business based in City A
  currently keeps a record of client and job
  details in a relational database. The owner
  decides to open a separate site in City B that
  will serve new customers. The City A site will
  occasionally need to access the City B customer
  data.
• (a) Describe one advantage of using a distributed
  database in this situation.2m
• (b) Describe one limitation of using a
  distributed database in this situation. 2m
• (c) Describe one advantage of using a client/
  server database in this situation. 2m
• (d) Describe one limitation of using a client/
  server database in this situation. 2m
• (e) The two sites will be connected using a
  public communications network.
• The owner is concerned about the security and
  privacy of the data on the system. Describe two
  methods that can be used to ensure such security
  and privacy.4m

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Distributed Databases Answer

• a) Distributed Advantage data is stored locally
  (1) this is the data that is used the most, so
  response time will be quicker/ means less network
  traffic between sites (1)
• b) Distributed Disadvantage need for each site
  to perform their own backup (1) meaning that a
  complete database backup cannot be assured (1)
• C) Client/Server Advantage increased security
  (1) access control/ backup occurs at the server
  (1) less powerful client machine required (1) all
  the work is done at the server (1)
• D) Client/server Disadvantage a powerful server
  is required (1) reliance on one machine (1) if
  there is a problem with the server, no one can
  work (1)
• e) Security and privacy Use encryption
  technologies (1) so that anyone getting hold of
  the data is not able to make sense of it (1)
  passwords/ logins (1) to deter casual access to
  the system (1)
• NB See Ch17 for client server databases