Examples of Communication Systems III - Electronic Commerce

pg 294
Financial transactions over an electronic network

·         ATM (Automatic Teller Machine)

·         EFTPOS (electronic funds transfer at point of sale)

·         Internet Sales

·         Internet banking

1.       For an ATM identify the collection and display devices it contains and the nature of the data they collect/display.

-display devices include the screen - often a CRT, although LCD screens are becomign popular, speaker.

- collection - magnetic stripe reader that collects magnetic information from the back of the customer's card

2.       List some possible methods of connecting an ATM to a network.
-ethernet
-data dial up modem
-

3.       For an EFTPOS terminal, identify the collection and display devices it contains and the nature of the data they collect/display.
-keypad
-magnetic stripe reader
-screen + printer -> output

4.       What protocol ensures the secure delivery of webpages during an internet banking transaction?
-HTPS & SSL
-transport layer security

5.       What is the function of server-side code indicated by the .shtml file extension of the internet banking pages?
-transmitts data to the server -> shtml webpage is customised by the server before it comes to the customer

6.       Describe three methods used to seek unauthorized access of internet banking accounts.
-Fraudulent emails
-Malicious software that records keystrokes such as passowrds and sends them to illegal operators. e.g. trojan and keystroke loggers
-Identity theft where a fraudulent person obtains sufficient information about another so that they can contact the bank, identify themselves as the other person and have the password altered.

7.       Identify some of the social and ethical implications of internet banking replacing face to face banking.

-changing nature of work

-equity and access

-age
-consulting can not be done online

8.       Define the term Virtual Business. What advantages do they offer to the business owner and customer. What concerns might customers have regarding online purchases?
-Virtual Business: employs electronic means to transact business as opposed to a traditional brick and mortar business that relies on face-to-face transactions with physical documents and physical currency or credit
-advantages : no rent, reduce overheads, flexible hours -> changing natue of work, ease of promoting, small business are able to efectively advertise on the internet.
-positives for cutomers: acces to virtual business 24/7, discounted products, product is posted to you
-negatives: reduce overheads of owner passes onto the customer, security of payments, reliability of receiving the product.

9.       Does online trading have any social or ethical implications? Explain.
- bound by fair trading
-change: flexibility
-unemployment
-retail outlets are suffering as deman for online businesses increase
-interpersonal relationship between the customer and business - customer loyalty

Examples of Communication Systems -Messaging

Refer to pages 274 – 292

1.       Which part of the PSTN network is digital, which part is analog?

Apart from the connections between telephones and their local exchange, the remainder of the PSTN is essentitally digital.

2.       Define multiplexing and identify how it increases efficiency on a digital network. Is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. The aim is to share an expensive resource. The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred.
-multiple conversations on a single wire

3.       What other features does a digital PSTN offer?
-call waiting, caller ID,

4.       Describe the basic principle of a Facsimile machine (FAX), use the words – scan, light source, sensor, transmission.

The basic principle of a FAX machine us to transmit data from one location to another. like morse code the message is sent as a serius of tones, one for white and another for black, these tomes were converted to an image using heat sensitive paper.
-scanner with a light source that the document is fed through, dark adn light area's are detected by sensor and are coded and transmitted to the receiver.

5.       Complete group task from page 277 – create DFD for voicemail system.

6.       Describe what is meant by a Phone Information Service – give four examples of a service they may provide. Where have you encountered such a system
-phone information service-  computerised service e.g. calling up phone centre's such as vodafone for information and you are met with a computerised voice.
-direct the caller to an extension of the system
-recording voice mail.
-text to speech/speech to text -> either u speak or write and an information system will either repeat what u have written or write in text what you have said.
-Fax
-Call logging to databases.
-Support for multiple incoming and outgoing lines

7.       According to the commonly used standard for IVR (Interactive voice response) identify the numeric key suggested for each of the following actions;

·         Conclude data input - - #

·         Indicating yes/no 1, 2/0

·         Cancel and return to previous step

8.       Both VOIP (Voice over Internet Protocol) and Instant messaging allow for the transmission of audio over the internet. How does VOIP differ from instant messaging? What are the cost components of a VOIP to VOIP call?
- instant messaging is pc to pc

-VOIP transfers voice calls over the public internet -> uses IP datagrams, makes a jump from the internet protocol to computers and telelphones.

9.       VOIP relies on several protocols in the communication and control layer. One is RTP – identify its role. Others are   UDP/IP – why is UDP used and not TCP?
-VOIP - communication control
-RTP -
-UDP/IP instead of TCP/IP - not lagging, speed, compression of data, doesnt perform error checking whereas TCP checks and makes sure data is intact. TCP is slower than UDP but UDP data does get corrupted.
UDP doesnt have processing overheads involved in error checking and therefore can stream teh data more quickly compared to TCP -> downside, some datagrams will be  corrupt.

10.   Typically what hardware would be used to enable the use of VOIP in a home?

11.   Summarise the advantages and disadvantages of VOIP.
Advantages:
-low costs for long distance calls.
-no additional cabaling required.
-requires an internet question
can originate from any location with an internet connection.
portability
Disadvatages:
- IP and internet form a packet switched network, which was not designed for continous delivery of real time data
-emergency calls cannot be made when there is a power failure.
-broadband connections are unreliable in terms of quality of service compared to the PSTN.

12.   Describe the role of the email Destination address fields, To:, CC: and BCC:.
-contains the address of the primary recipients of the message.
- these are the people who the message is directly written to.
-Cc: is short for carbon copy - they receive a copy however the message is not directed at them.
-Bcc: blind carbon copy - those who also recieve the message but their addresses are not to be revealed to any other recipient.

13.   Describe the Date:, From: and Sender: Originator fields.
-Date: must be included and is used to specify the date and time that the user indicated that the message was complete and ready to send.
-From: contains multiple emal addresses, it is possible for a message to be sent from more than one person.
-Sender: used to specify the single email address that actually sent the message.
e.g senior management may formulate an email message that is actually send by a secretary. the From field would then contain each managers email address whilst the Sender field would contain the secretary's email address.

14.   What is the general purpose of Identification Fields?
-used to identify individual messages and to allow email application to maintain links between a thread of messages. they are designed for machines to read rather than humans ->3 possible indentification fields - MessageID, In Reply tp and Reference

15.   Informational Fields in emails are optional, however one is typically used. Name this field.
Subject field

16.   “MIME (Multipurpose Internet Mail Extensions) is a protocol used to code non-textual data” – what does this mean? Give examples of the non-textual data.
-protocol used to code non-textual (not text) data and attachments into ASCII (characters on the keyboard) so that it can be transmitted within email messages.
-transmission of many foreign language characters that cannot be represented using the 127 7-bit ASCII characters.
-type of extention
-coding nontext data as ASCII code text

17.   What code does the MIME format use to transmit data?
ASCII

The Communication Framework (pg 232 - 237)

the functions performed within the communication systems in passing messages between source and destination, including:

– message creation:

• compiled at the source in preperation for sending that takes place using some type of software app adn involves the collection of message data from on teh system's user or participants. e.g.  user writting an email using an email client such as outlook. web server retrieving requested HTML files from secondary storage in preparation for transmission to a web browser.

– organisation of packets at the interface between

source and transmitter:

• when a messagr is being prepared for transmission it descends the stack of protocols from the application level down to where it is ready for physical transmission by the hardware operating at the transmission level. Each protocol wraps teh data packet from the layer above with its header and trailer.  Protocols withins each layer are applied independently of the protocols operatin in other layers.
• the message is then passed on to the communication control and addressing level.
• at the receiving end the process described aboce the essentially reversed - each protocol strips off tis header adn trailer, performs any error checks and passes the data packet to the transmission level protocol(s).

– signal generation by the transmitter:

• the transmitter is the physical hardware that generates or encodes the data onto the medium creatnig a signal.  in most cases transmitters and recievers are contained within the same hardware device - receiver decodes the signal on the meduim.
• Hardware is controlled by protocols operation at the transmissionlevel.
• the main task of the transmitter is to represent individual bits or pattersn of bits as a wave - this wave is the signal that is actually transmitted through the medium.
• E.g. that include transmitters are: NIC's, switches, routers, ADSL, and cable moderns, mobile phones and bluetooth devices.

– transmission:

• occurs as the signal travels or propagates through the medium. each bit of often pattern of bits moves from transmitter to receiver as a particular waveform. Transmitter creates  each waveform and maintains it on the medium fro a small period of time.
• 1/5 of a second is the time requied for the physcail transmission of one megabyte  of data or binary data uf the transmission occurs as a continuous stream of symbols and the transmitter and receiver are physically together.
• in reality - data is split into packets, which are nto sent continuously, errors occur that need to be corrected and some mediums exist over enormouse distances - e.g. satelites or across oceans.
• some protocols wait for teh acknowledgment from the receiver before they send the next data packet.

– synchronising the exchange:

• to accurately decode the signal requires the receiver to sample the incoming signal using precisely the same timing used by the transmitter during encoding. this ensures each symbol or waveform is detected by the receiver. if both transmitter and receiver use a common clock then transmission can take place in the knowledge that sampling is almost perfectly synchronised with transmitting.
• e.g. system clock is used during synchronous
• synchronous transmission systems have almost completely replaced older asynchronous links which transfered individual bytes seperately using start and stop bits. Synchronous communication does not transfer bytes individually; rather it transfers larger data packets usually called frames.
• 2 elements commonly used to assist he synchronising process:
  -Preamble - can be included at the start of each fram whose purpose is iniial syncronisation of the receiver and transmit clocks.
  -second element is inluded or embeded within the data and is used to ensure synchronisation is maintained thourgh tranmission of each frame.
• manchester encoding: transition repersented through 10baseT.

– addressing and routing:

• each new communication link will have its own protovol or set of protocols and hence each packet must ascent the protocol stack untill it reaches the addressing or routing protocol adn then desend the protocol stack as it is prepared for transmission down the next path.
• Ethernet and other transmission level protocols use the receiver's MAC address to determine the path leading to the reciever.
• e.g. ethernet switch maintains a table of all the MAC addresses od attached devices. Frames can therefoer be directed down the precise connection that leads to the receiver. most routers use the IP address withing the IP datagrams together with their own routing table to determin the next hop in a datagrams travels.

– error detection and correction:

• As messages descend the stack prior to tranmission many protocols calculate checksums or CRC (Cyclic Redundancy Check) calues and include them within their headers or footers. Once the message has been received it ascends the protocol stock where each protocol examines its own received headers and trailers.
• If error detection is used by the protocol then the error check calculation is again performed to ensure the result matches the received checksum or CRC value. Whenever as error is detected virtually all protocols discard the entire packet and the sender will need to resend the packet to correct the problem.

– security and management:

• Many protocols restrict messages based on user names and passwords, and other go a step further by encrypting messages durign transmission.
• e.g. POP (Post Office Protocol) operates on most mail servers. Top retreive email messages from a POP server the user must first be authenticated - meaning a correct user name and password combination must be included.

For each example below, identify the source, destination and medium over which messages are sent. Describe suitable communication rules (protocols).

1.       A conversation with a young child

2.       Sending a birthday card to your Grandmother

3.       Watching television

4.       Ordering a meal in a restauant