CISA made Easy - Easy CISA Preparation: IT Service Delivery

Showing posts with label IT Service Delivery. Show all posts

Friday, September 19, 2008

Presentation Layer - Data Security and Formatting

Over a network different types of information are transferred. Have you ever thought which layer deals with formatting and syntax checking of these information. As discussed in my earlier article about Application Layer (Layer 7 of OSI model) which deals with different applications (protocols).Thus the question arises that where and which layer of OSI model decides that a particular type of information has to be converted to a particular format by following a particular syntax. Answer is Presentation Layer (Layer 6 of OSI model). For example this layer decides that what will be http encoding and format (Remember http is a layer 7 protocol ). So, the layer deciding encoding must reside immediately below the layer 7. So, the Presentation Layer is the Layer 6 of OSI model. It converts a particular picture information received to gif format, a particular movie information received to mpeg format.

Question: Which Protocol or a set of protocol function(s) at Presentation Layer ?

Answer: No protocol functions at Presentation Layer.

Functions of Presentation Layer includes:

1. Data Formatting & Syntax Checking - Presentation Layer converts information received from Application Layer(Layer 8 of OSI model)to standard formats and syntaxes.

2. Support to all major formats & Services - Presentation Layer support all important formats like ASCII, EBCDIC,MPEG etc.

3. Data Security - Information received may be encrypted or decrypted by using Cryptographic principles. Thus this layer provides data and information security within OSI framework

4. Data Compression & Decompression - data can be compressed or decompressed as required by Presentation Layer

5. Communication with Application Layer and Session Layer- It receives information from Application Layer and syntactic, formatted, compressed and encrypted( whichever applicable) data is sent to the Session Layer (Layer 5 of OSI model).

Architecture of Presentation Layer-

Presentation Layer has two sublayers - Common Application Element Sublayer & Specific Application Element Sublayer.

Abbreviations used:

OSI - Open Systems Interconnection
HTTP - Hypertext Transfer Protocol
ASCII - American Standard Code for Information Interchange
EBCDIC - Extended Binary Coded Decimal Interchange Code
MPEG - Moving Picture Experts Group
GIF - Graphics Interchange Format

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Friday, August 22, 2008

Important points to remember about OSI – Application Layer

The Application layer of TCP/IP suite corresponds to combination of Application Layer, Presentation Layer and Session Layer of OSI Model. This article intends to discuss briefly the Application Layer of OSI model.

Application Layer is highest layer /7th Layer/Closest to user layer of 7 OSI layers.

Many people think that Application Layer will contain different applications. Application Layer does not contain any application. It contains the protocols supporting different applications.

If an application A has to work over networks, required data and related instruction needs to be sent. Here role of Application Layer comes into picture. Application layer sends the required data and related information to the protocol(s) supporting application A and not to the application A. In this way data and instruction is sent to lower layer and request is sent to the Presentation Layer(Layer 6).

Application Layer defines message types, message formats, semantics and rule sets for communication between user and application. Application layer also controls communication between application and user.

There can be two types of application layer protocols.

1.CASE

2.SASE

Some common protocols sitting in Application Layer are:

FTP

Telnet

SMTP

DNS

DHCP

Summary:

1. Application layer connects user and applications.
2. Application Layer helps in communication between different applications through protocols supporting those applications.
3. It controls the exchange of information.
4. Application layer handles semantic conversion between applications
5. File Transfer, Virtual filing, job/message transfer are also addressed by Application Layer.

Abbreviation Used:

TCP - Transmission Control Protocol

IP – Internet Protocol

OSI- Open System Interconnection

SMTP- Simple Mail Transfer Protocol

FTP- File Transfer Protocol

DNS- Domain Name service

CASE - Common Application Specific Elements

SASE- Specific Application Specific Elements

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Friday, July 11, 2008

Data Integrity for CISA Exam

CISA Quick Tips: 008-1107
A good Database Management System (DBMS)must ensure completeness,accuracy,authenticity,correctness and relevancy of data it contains.
To ensure this various machinisms / constraints are being used by various DBMS like:

1. NULL/NOT NULL
If a field is defined as NOT NULL, every row of that particular field will contain some value of defined data type.
Note: Zero '0' is not a NULL character.

2. UNIQUE
If a field is defined as UNIQUE, no two rows of that field will be identical.

3.PRIMARY KEY
Primary key means UNIQUE & NOT NULL

4. FOREIGN KEY
It represensts refrential integrity. Primary key of one table can be used to connect to other table with similar values.
By above we achieve data integrity. There are many other wasy to ensure data integrity but above four should be very clear to you.

CISA Type Question 08-1107
An IS Auditor while auditing a Relational Database Management System (RDBMS) finds the following description of a Name field:

field name constraint
---------------- -------------
Name UNIQUE & NULL

He verifies the table and the table contains following values in the name field
Name
i. Alex
ii. Rahul
iii.
iv. Alex Parera
v.
vi. Rajeev

Which of the above violates the data definition for Name column ?
1. i and iv
2. iii and v
3. ii and vi
4. more than one of the above

Answer to CISA Type Question 08-1007
Correct answer is 4. None of these.Refer to CISA Quick Tips 08-1007

Further Reference:
1. CISA Review Manual by published ISACA
2. http://www.isaca.org

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Thursday, July 10, 2008

Bridges for CISA exam

CISA Quick Point 08-10-07

I am happy to receive your comments and a slight confusion.Some one wanted to know about number of ports in repeator.

I have seen 4, 8 and 16 ports repeaters only.They also wanted to know about difference between Repeator and bridge.

So, I thought this is the right time to discuss about bridge in brief.For CISA exam you need not know in depth but yes clarity of thoughts and a clear basics about each topic will help you a lot.
Never be negative while your preparation and then I guarantee for your success.Also be regular in your studies.

Let us know about Bridge.

Repeators, Hubs and Bridges are similar but they have got fine line of difference.

For example,

bridge works on Layer 2 whereas repeater and hubs on Layer 1

Repeaters boost amplitude and frequency and bridges connect/bridge one LAN segment to other LAN/WAN segment.

Bridges deals with MAC address (not the IP address.remember IP will come at Layer 3)

We can configure software based switches but repeator generally can not be configured like that.

Bridges deal with frames where as repeator with bit-streams

With development of good switches the use of Bridges has gone down.

The following diagram will further clarify you about bridges.

With this I guess now you will ask the difference between Bridges and switches ?

Do not worry about other LAN components and be clear about repeaters and bridges first.

CISA Type Question 08-1007

Which of the following is false about a Bridge?

1. It deals with MAC address.

2. It sends data frames

3. It can be used to connect a lAN segment to other LAN/WAN segment

4. None of these.

Answer to CISA Type Question 08-0807

All of the points are correct but repeater generally fail to manage complex traffic. so, the correct answer is 4.can manage complex traffic across networks.

Further Reference:
1. CISA Review Manual by published ISACA
2. http://www.isaca.org

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Wednesday, July 9, 2008

Repeator a LAN device for CISA Exam

CISA Type Point 08-0807:

If you are not an expert in networking you need not worry. I shall try my best to present you the concepts in simplest form. Today i shall be discussing Repeator, a LAN component/device.

Repeator is basically amplifier which ies bitstreams from one media segment to another of a network (LAN).

I have said every thing about a repeator in one statement.

Now i shall explain some important terms of above definition in brief.

1. amplifiers - repetition of signal amplitude and frequency
in simple words repetition or amplification of bitstreams.

2. Bitstreams - Layer 1 of OSI deals in bitstreams.
which also tells us that repeator works at Layer 1.

3. Segment - repeator conects two segment of a Local Area Network

Even if you are not very much aware of terms like LAN & OSI. My future posts will contain a simplified tips on them. Do not worry about these terms at this moment.

The following diagram will clear the concept of repeater further:

CISA Type question 08-0807

Which of the following is NOT the function of repeator ?

1. Increase the number of ports of a LAN
2. Works at data Link layer of OSI(Layer 2)
3. deals with bitstream amplification and connects multiple cable segments
4. Can manage complex traffic across network
5. None of the above.

Note:all of you are requested not to know only the correct answer but try to read and understand each choices before answering the question. Remember if you do this for all the questions from now, nothing will prevent you from passing CISA exam and each choice will increase your knowledge. and this is the secret of passing examinations like CISA. So, choices are equal (even more) important than the questions.

All the best again.

Answer to CISA type question 22

Data dictionary describes/contains all of these so, the correct answer is 4. A, B, C,D &E.

Further Reference:
1. CISA Review Manual by published ISACA
2. http://www.isaca.org

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Tuesday, July 8, 2008

Data dictionary for CISA exam

CISA Quick Tips 22:

This is an easy topic and I believe easy topic like this should be carefully studied. People often do mistake in easy topics.

Before knowing data dictionary let us know what is metadata ?

Most of you will say data about data and this is the best definition of metadata i know.

As the name suggests data dictionary is dictionary of database in Database Management System(DBMS).

In file based DBMS data dictionary will be set of files which contains information about other files and in Relational Database Management System, the data dictionary will contain set of tables and processes which contains information about other process and tables.

Besides information about tbles/files Data dictionary contains
1. Policy, Procedure & Processes
2. Structure and Organization. of database

CISA Type Question 22.

Audit of data dictionary could be the best tool to study which of the following?
A. Growth of database
B. Database Usage Pattern
C. Structure & organization of the database
D. Process, Policy and Procedure of database
E. User rights and profile study

Correct answer is
1. A, C &D
2. B, C &D
3. B, C, D &E
4. A, B, C,D &E.

Answer to CISA Type Question 21.

Before using ITF what is the MOST important thing that an IS auditor should see if the live database and even the application is backed up or not. So, the correct answer is 2. He should ensure the presense of latest backup of database and application.

Programming code and structure study does not com in the purview of most IS audits.

Further Reference:
1. CISA Review Manual by published ISACA
2. http://www.isaca.org

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Thursday, June 26, 2008

ACID Property of Database for CISA Exam.

So, far I have tried to present few topics in easiest manner. I do believe

if we go ahead like this Upto next CISA exam we will have all the ingredients

for revision. and in year to come this will be a must for every CISA aspirants.

In any case ISACA's CISA Review Manual is the key for your success. This blog

will help you in the best utilization of Review Manual. I request all of you

to order for your copy of ISACA's CISA Review Manual at http://www.isaca.org

well in advance of your CISA Exam.Remember CISA Review Manual is a sea.

Here is another important CISA Quick Point and CISA Type question

CISA Quick Tips 13:

Here is the easiest way to learn about ACID Property of Database.

ACID Property of Database means

Atomicity

Consistency

Isolation

Durability

Atomicity:

Means All or None.

Which means a database transaction will be either complete or NIL and

never in between. Please, see the following diagram:

If A=5 and we have to add another 5 to A.

A will be 10 if transaction is complete otherwise A will remain 5.

Never anything else.

Consistency

All integrity constraints or integrity rules will be taken care by all transaction.

For example let us discuss the following table

Here Roll_No is primary key. Primary Key means unique and not null. If we

try to insert a new row with the value 001 in Roll Number field.It will be

aborted and not be inserted. Database will remain in their earlier state.

Isolation

All transactions will be separate and there will not be any effect on other transaction(s)

Durability

If a transaction is commited, it will be durable and not be rolled back.

CISA Type Question 13:

An IS auditor while auditing an Relational Database management System

(RDBMS) finds some disparity in value of same field in two tables.

This is MOST likely against the principal of

1. Atomicity

2. Consistency

3. Isolation

4. Durability

Answer to CISA Type Question 12:

Generally Hot Site will have all the System Software, some application software, servers, backup devices and other necessary hardware, most of the networking and communication components.The only missing thing could be last Data Backup and System documentation which will be under main site control .

So, the correct answer is 4. all documentation and data backup.

Further Reference: