Tutorial 7 Detailed Review Questions

Chapter 4

After the 802.3 Working Group creates a new candidate standard, what steps must the candidate standard go through to become a full OSI standard? When do vendors begin building products?

Steps to go through include the following:

1. IEEE ->ANSI->ISO and ITU-T before becoming a full OSI standard.

ii. At the point when the standard is official.

How many wires are there in an 802.3 10Base-T/100Base-TX wiring bundle? How many are actually used in transmission? How would you answer if someone asked you what "Cat 5" means?

A bundle of four UTP pairs. ie. eight wires in total. Actual number used is 2 per transmission. Cat 5 means more twists per inch of wire thus reducing cross talk interference at high speeds. The higher the Cat the more twists per inch.

What is the size of address fields in 802.3 MAC layer frames? Why does every
NIC have a unique 802.3 MAC layer frames? What is the maximum size of these frame? What is in the data field of a typical MAC layer frame?

1. Size of address fields is 48 bit.
2. It ensures that, across NIC vendors, the default address preset at the factory will be unique of every NIC

produced and hence no two same addresses.

iii. Maximum size of these frames is 1518 octets. Minimum size is 64 octets.

iv. The Logical Link control is usually in the data field of a MAC layer frame.

Chapter 5

Distinguish between permanent virtual circuits (PVC) and switched virtual circuits (SVC).

• As the name suggest PVC has permanency in its communication with another station. It is used everytime a connection is being made.
• In contrast, SVC is set up only when 1 station wishes to connect to the other. ie the SVC varies per connection made

In ISDN, distinguish between the Basic Rate Interface (BRI) and the Primary Rate Interface (PRI).

BRI mulitplexes 3 channels to the desktop:

• Two 64 kbps "B" channels (to carry user data)
• One 16 kbps "D" channe for supervisory communication
• It is communcation within the customer premises

PRI in based on more channels, possible combinations are:

• 23 64kbps "B" channels + 1 64kbps "D" channel
• 30 64kbps "B" channels + 1 64kbps "D" channel
• it is exists as communication between customer premises and the ISDN carrier.

How do speeds of Frame Relay and ATM compare?

Frame Relay speeds are generally slower than ATM. Quantum is as follows:

• Frame Relay : 64kbps - 10 Mbps
• ATM : 25 Mbps - a few gigabits per sec

However Frame Relay speeds often suffice corporate needs and are priced aggressively.

Tutorial 7 Thought Questions

Chapter 4

1. To list all the additional hardware and software needed for a simple PC network. Organisation wishes to use email, word processing, file sharing and print sharing with one existing printer.

Hardware	Software
Ethernet 802.3 10Base-T &/or 100Base-TX UTP wiring (8 wires)	Server operating system (Unix/Novell/Windows NT)
Switches/hubs	Application s/w (Windows 2000/Red Hat Linux)
NIC for all PCs	Printer software
File, email and application servers

2. Explain the steps a receiving station takes when it receives an Ethernet 802.3 frame NOT intended for it. List each field encountered in order and tell what the receiving MAC layer process does with it. Make each field a separate paragraph.

Preamble field and start of frame delimiter field

Frame begins with these two fields. Purpose is to synchronize the receiver's clock.

Preamble has 7 octets of 10101010 for synchronization, frame delimiter 1 octet of 10101011 to start frame.

Destination and source address field

MAC layer frame uses a 48-bit source address and destination address. 6 octets for address receiving station.

Length field

No specification of fixed length for frames. 802.3 MAC frame has 2-octet length field, which tell the number of octets in the data field.

Data field

This field holds the information being sent and contains the PDU of the next higher layer ie the Logical Link Layer (LLC)

PAD field

Required to "fill up the space" to achieve a minimum of 64 octets.

Frame check sequence field

To keep the error rate very low, the MAC frame specifies a four octet error-handling field, the frame check sequencing field. The transmitting station performs a calculation on the remaining bits and places the results in the frame check sequence field.

The receiving MAC layer process redoes the calculation and determines if the results are consistent with the frame check sequencing field. If results are consistent, the receiving MAC layer process accepts the MAC frame.

If the results are inconsistent, the MAC layer discards the MAC layer frame. No retransmission request occurs. Rightfully, a higher-layer process must detect a problem and retransmit the lost information. 802.3 MAC layer offers only error detection not correction. The LLC layer will offer error correction capabilities.

3. Explain the steps a receiving station takes when it receives an Ethernet 802.3 frame intended for it. List each field encountered in order and tell what the receiving MAC layer process does with it. Make each field a separate paragraph.

Each field encountered does the same for the above question except for the frame check sequence field. MAC layer will accept the MAC frame and the process continues in the LLC layer.

Chapter 5

1. How do virtual circuits reduce costs?

Virtual circuits are connection-oriented transmission services. It forms a single path across multiple switches.

It reduces cost possibly in the following ways:

1. Virtual circuits provide ATM frame addresses to reduce congestion and latency thus the need for more hubs or swtiches
2. Virtual circuit numbers in ATM frames inherently provide better connectivity

2. Evaluate each option in terms of performance, cost, and technical feasibility. Select a good working solution for the college.

Option	Performance	Cost	Tech feasibility
Ethernet 10Base-T	Low	Low	Limited in distance (200m) and usage capacity
Ethernet 100Base-TX	Moderate	Slightly more option 1	Limited in distance (200m) and usage capacity
Switched 10Base-T Ethernet	Moderate	Low	Switches eases congestion. But Still suffer proximity problem.
Switched 100Base-T Ethernet	High	Slightly more option 1	Switches eases congestion. But Still suffer proximity problem.
ATM	High speed	High cost	More for corporate usage with high speed and deep pockets
Routers		Low

Choice must take into consideration scaleability and cost.

Optimium choice for a "Switched 10Base-T Ethernet" as it accommodates the usage capacity (thru switches) and proximity problem (use of at least 3 hubs). Speed will be slower as this is impossible with a "Switched 100Base-T Ethernet" solution as its inherent limitation is only 2 hubs (ie distance of 200m)

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Tutorial 8

(Communication on Intranets and other Networks)

Detailed Review Questions

What is the disposition phase in email? Why is it important?

• The disposition in the email exists as after a message is received. It is a phase where most email commands are issued.
• It is important to have an automated disposition phase as productivity can be improved.

What is electronic document management? Distinguish between full-text searches and index searches. Why do you need a retention strategy? In group memory, why is design rationale important?

• Managing of documents in electronic form by maintaining a systematic, consistent and accessible storage of digitized documents. It utility is enhanced in groupware.
• Full-text search consist of retrieving the full version of the text in the query. Index searches are more specific to a particular phrase or paragraph.
• A retention strategy is required to determine how long different group output will remain in the system ie to remove it when no longer needed. This reduces storage costs and expedites the search for documents.
• Design rationale systems are important because considerations such as cost, storage space, productivity and continuity of the system are affected. It helps to retain information on the design alternatives considered and the pros and cons of each. In addition, it allows the team to revisit its decision later and also understand why certain design decisions were made.

What is group calendaring? Why is it needed? Why is it difficult to implement?

· Group calendaring is the coordination of the availability of individuals on certain dates.

· It functions as a organisor that schedules meetings and can even inform involved personal through email.

· It is difficult to implement as it requires everyone to keep his/her availability schedule up-to-date. This is seldom achieved.

Distinguish between workflow and project management.

· Workflow management relates mainly to routine clerical tasks (at all levels) that are usually high in volume.

· Project management relates to ad-hoc tasks that involve high level managerial and professional coordination. Such tasks are more dynamic and complex in nature.

(workflow systems track individual tasks sequentially)

In Lotus/IBM Notes, explain replication and scalability.

· Replication is gives the advantage of resource sharing. Users or groups throughout the organisation can access the information so long as it resides in a Notes server.

· Scalability gives the utility the advantage of adding new components to cope with new demands of the organisation. In Lotus/IBM Notes, this is often present in the broad and constantly emerging modules that one can add.

What are the advantages of combining groupware with telephony.

• The possible advantage is the availability to convert text to voice and vice versa. This enables more productive use of time. Call centers utilise computer-telephony integration (CTI) to expedite handling customers and maximize human resources.

Thought Questions

At what layer in the TCP/IP-OSI hybrid architecture would you find e-mail standards?

· The e-mail standards will reside in the Internet layer this is because the mail standards are in the TCP/IP architecture.

Why do you think e-mail has grown so explosively while more sophisticated groupware products have lagged? Do not limit yourself to what was said in the text.

Email has grown rapidly because of the following factors:

· Internet Mail Standards like SMTP govern it use.

· It is very user friendly and is as simple as 'posting' a letter.

· It is individualistic in nature, everyone has a private mail account.

Groupware has lagged behind because:

· It requires a group to utilise it before its benefits are realised.

· It is very specific to corporations and are only essential in corporate environments.

· Various objectives are served by plethora of groupware available.

You want to send someone an attachment. What things should you negotiate beforehand?

· The email account settings of the receiver as it may have size restrictions.

· The internet encoding scheme of sender and user must be common.

· There must also be an agreement pertaining to the application file format so that the recipient can access the file

What groupware services would you like to have for a team designing a new software product? Explain.

· Email for fast and simple communication.

· Video-conferencing (if the personnel involved are from diverse geographic location)

· Project management to coordinate phases and adhere to timelines.

· Electronic document management to organise phases of software development.

· A bulletin board for placing concerns and issues in relation to project.

· (size of team, location of members, degree of coordination required)

Projects

E-Mail Usage	A survey of 436 U.S. adults using computers found that: 84 percent of home users and 83% of work users used e-mail in the last 3 months. 82% used e-mail to communicate with friends, 56% with co-workers, 47% with business clients, and 39% with their boss. Associated Press, "Computer Users Use E-Mail to Reach Out and Touch Someone," August 13, 1998.
Communication Interruptions	A survey of office workers at many levels by Pitney Bowes found the following averages: Respondents used 8.7 communication tools. Of their primary communications methods or tools, 72% were electronic and 28% were paper. They communicated with 24 people per day. Respondents sent or received 190 messages per day. They were interrupted by messages 6 times per hour. 34% of these message disrupted work 45% were feeling overloaded by the number of messages received. Pitney Bowes, Pitney Bowes Workplace Communications in the 21st Century, 1998 study, May 1998.
@	Who decided to use the @ sign in e-mail? It was Ray Tomlinson, who wrote the first e-mail program to work across multiple hosts. This was in the early 1970s.

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Tutorial 9

(Larger Networks II: Servers, Management and Security)

Detailed Review Questions

What is 24 x 7 operation? Why is it important for some applications than for others?

· 24 x 7 operation occurs when computer systems need to be operating all the time and no downtime or shutdown is allowed.

· Certain applications require this feature as they may support mission critical services of the organisation. Eg.

· A bank needs such operations to run its ATMs and update its dbase in real-time.

· Airports need flight monitoring systems to be operational all the time.

In geographical decentralization, distinguish between replication and caching.

· In geographic decentralization, server replication and data caching promote greater efficiency (time/speed/load adv's) as client PCs utilises server nearest to them.

· In replication, the main server's entire content is made available at each remote server. May pose a question of redundancy.

· In caching, only some webpages are made available at remote servers.

· Replication and caching options require cost (of server and maintenance) benefit (efficiency) analysis. Also to consider directory server use to aid user in locating resources.

Characterize each of the following: fault management, configuration management, performance management, security management and accounting management.

Key objective of the following management technology is to move bits efficiently, effectively and securely amongst computers in a network.

Transmission Management Techniques	Capabilities of Management Program
Fault Management	Id cause of network failure => take action to circumvent area of fault. Program to expedite task of identifying root fault.
Configuration Management	Looks at specific operation of each component. Ensure optimum performance and utility of component. Maintain an inventory of its network components.
Performance Management	Measures speed and reliability for indv. Component. Offers 'what-if' analysis to bring abt more desirable configurations & arrangements.
Security Management	Prevents unauthorised access. Keeps private key in secure storage. Manages encryption techniques, filtering information, firewall settings and administers security policies.
Accounting Management	A management accounting perspective of assigning network cost to various dept/users eg via activity based costing

What are the major threats to security?

· Power failure => may lead to legal suits, lost data, exposure to security threats.

· Unauthorised access within the network and from outside the network

=> sensitive information may be compromised

· Viruses upsetting the function and resources in the network

· Message integrity is lost by interception of original message and a change in its content.

How many times does encryption take place when you send a message with a digital signature? List each, and explain whose private or public key is used and what this encryption accomplishes.

It takes place twice.

· Once for encryption of the message digest (digital signature) using sender's private key.

· this achieves the authentication of signature when the message digest is check to ensure that its contents tally with the original message

· The other encryption takes place when the digital signature is attached to the entire message and sent as a whole message. This uses the receiver's public key.

· this achieves the encryption of the message which is still require to prevent unauthorised access.

Thought Questions

Why is intrusion detection central to security?

Intrusion detection is central to security because:

· It helps promote damage control of any impending intrusions by alerting the network administrator.

· Such a system can also archive possible intrusion strategies and pre-empt possible attacks. (Prevention is better than cure)

· It promotes evolution of the security features in the network.

· It identifies weak spots to strength them to prevent possible intrusions.

· Self-security analysis tool can aid in attacking the systems to further enhance security.

· Detection must also be within the organisation via audit trails that record where users have gone and what information they have accessed.

If you and I wish to communicate via public key encryption, what do you have to know? What do I have to know?

In encryption of messages to you:

· I don’t have to know anything but your public key. You should possess your private key to decrypt the message

· I would also need to know how secure I want the encryption to be. The higher the need for secured transmission the higher bit length (2 bit - 128 bit) I would employ.

In authentication of messages to you:

· I need to know place my private key in my message. You would need my public key to authenticate the message.

If I send you a message, I normally encrypt it with your public key. However, I could also encrypt it with my private key. You could decrypt it with my public key. This would work, but it would cause a serious problem. What is that problem?

The problem is that once the receiver is able to decrypt my private key he has knowledge of my encryption method.

Why do you think network management has taken so long to develop?

· The business environment is becoming more complex and dynamic that no network management can be comprehensive enuf.

· Customisation to specific business needs is likely to be an alternative.

· Many vendors con up with their own standards

· There is added advantage of a comprehensive network program that can exploit the characteristics of different network management protocols.

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TUTORIAL 10

DATAWAREHOUSING AND DATAMARTS

Describe the three types of metadata that appear in a three-layer data warehouse architecture. Briefly describe the purpose of each type of metedata.

The three types of Metadata are:

Operational Metadata

· describes the data in the various operational systems or sources that feed the EDW

· they exist here in various formats and are usually poor in quality

· variations due to different sources data is collected from

· should try as much as possible to improve quality at start so that downstream data related resources are not adversely impacted => TQM

Enterprise Data Warehouse (EDW) Metadata

· Describes the data in the EDW

· Includes description of the reconciled data

· As well as the rules for transforming ops data to reconciled data

Data Mart Metadata

· Describes the derived data layer

· As well as rules for transforming reconciled data to derived data

Describe 5 errors and inconsistencies that are commonly found in operational data.

Inconsistent key structures

- primary keys for tables are different

Synonyms

- same data values have disparate key names

Free-form fields versus structured fields

- the same data captured is expressed in different fields

Inconsistent data values

- data values are from varied sources and hence no integration

- data values are inconsistent

- data collection efforts are not orchestrated

Missing data

- data that is supposedly to be present be has been left out or not captured

Explain the use of facts, dimensions and attributes in the star schema.

Star schema exists in data marts to optimize the presentation of data through fact and dimension tables.

· Fact tables contain hard facts or quantitative data about an entity.

eg. pdt_code, units_sold, dollars_cost, dollars_sold.

The granularity of the fact table is an impt design factor that determines the depth and intended use of the data.

Non-key attributes may exists in fact tables and are called data columns.

· Dimension tables hold descriptive data about the business

eg. color,size, year, month,mgr, telephone, address

Attributes exist as descriptive data in dimension tables.

Different classification of data into fact and dimensions tables are characteristic of star schemas. One-to-many relationships are between dimension to fact table.

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TUTORIAL 11

DETAILED REVIEW QUESTIONS

How do active webpages make web-enabled database applications more attractive?

· Active webpages allow the user to select the type of presentation and query for data to be retrieved.

· Query can be made more attractive by use dynamic query options.

· Presentation can be made more attractive with use of graphics

What do SQL and ODBC both do? How do they compare? What is middleware? Why does it simplify application development?

· SQL merely specifies the how to query the database. The request-response exchanges exists in different proprietary ways. Moreover, it doesn't specify the full format of the request and response messages. Additional request protocols are require to manage such exchanges. SQL is a standard for query.

· ODBC is like a "translator" in a C/S environment where different database application programs exists (eg Oracle, SQL, Access). ODBC is a standard for database interactivity.

· Middleware is an application program that translates formats of one dbase to another.

· It simplifies application by

Ø Handling interactions bet the transport and network layers for the s/w developer.

Ø Limiting the amt of expertise the developer of dbase/network needs.

Ø Linking modern RDBMS servers with older legacy systems

What is networked object oriented programming? Why is it attractive? What is the standards situation in networked OOP?

· Network OOP is a programming that contains both data and logic to process the data in components called objects.

· Its attraction stems from the ability of objects to communicate and perform task more efficiently and effectively.

· There are too many standards governing network OOP.

Explain the concept of best practices? How does ERP help companies implement best practices?

· Best practices are business process that have been tried and testing and found to be superb in expediting tasks.

· ERP embodies the best pracs in each area. eg in HR, inventory, payroll, executive DSS, => in these areas they try to use what research has shown to be the best algorithms, practices and workflow.

Distinguish between SSL and SET. In what way is SET supposed to be better for customers? Is it really better in that way?

· SSL doesn't protect the user from abuses of his information by the vendor/seller.

· SETS provides such a protection thru liasing with a 3^rd party for verification of buyers particulars. (loophole that merchant will ask for buyer/user's credit card number)

Name and briefly characterize the main types of software you will need at an electronic commerce website?

Web programming+design software/multimedia/database/server os/transaction processing software/search engine/perf monitors.

THOUGHT QUESTIONS

Comparing adhocracies, virtual corporations and international organizational systems, in what order do you think they will appear? Justify your reasoning.

1. virtual or international

2. adhocracies

· The rational for the sequence is be'cos the virtual and international organizations will first form to promote greater flexibility in business.

· After which, they require X-fxnal teams to handle corporate relations and projects.

· However, given the dynamic business environment. There is no certainty of order they will appear in.

Why are marketing channels central to e-commerce strategies?

· Marketing channel serve to bring about aware of a website. The web is like an endless road and without marketing there is no way of telling were to go for what.

· Moreover, marketing is also important in building a brandname.

· This is crucial to enhance the element of trust and increase hits at a website.

Give your own assessment of the validity of customer concerns about credit card fraud in Internet electronic commerce.

· Valid concerns b'cos Bill Gates card number just got compromised. Smart hackers don't boast abt it. They take gradual expenses or sell your card info. You won’t know when damage is done

· Limited liability clause just pacifies the customer financially but psychological effect of trust on the web is already crippled.

Give your own assessment of the validity of customer concerns about the privacy in Internet electronic commerce.

· We are not techies and if our computers get hacked into we wouldn't know.

· eg, Singnet covert activities were claimed to be for customer's good to check if hackers can actually hack a computer are doubtful.