Note: We have tried solving the question paper in a very short time span as per our understanding and the study material we had. Feel free to contact us through comment box or through email if you have some descriptive answer.

Q1. Answer the following questions in brief                                   
A. What are the two ways by which public cloud helps the customers to reduce their IT costs?
Answer:

1. Flexible billing models enable customers to pay only for what they use.
2. It reduces the capital expenditures required for setting up the infrastructure.

 Practice Question - What are the components of a cloud computing environment?
 Answer: client, application, platform, infrastructure, server

B. What are the two limitations of SKI Virtualization?
Answer:

1. It is not possible, for instance, to run different versions or even different patch levels of a particular operating system on the same machine. 
2. Whatever versions exist in the host, that same software will be provided in the guest. SKI also sacrifices the security and reliability provided by other virtualization  methods. 

C. A company interested in cloud computing is looking for a service provider who offers a set of basic services such as virtual server provisioning and on-demand storage that can be combined into a platform for deploying and running customized applications. What type of cloud computing model fits these requirements?
Answer: Infrastructure as a Service.

D. How can a software development company leverage the PaaS cloud computing delivery model?
Answer:

Q2. Answer the following questions appropriately.
A. What is 3 - 4 - 5 rule of cloud computing?
Answer: This 3 - 4 - 5 rule stands for:

3 cloud service models
4 deployment models
5 essential characteristics of cloud computing infrastructure

RULE 3 - Cloud service models:
IaaS (Infrastructure as a Service):
The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications.
The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly limited control of select networking components (e.g., host firewalls)

PaaS (Platform as a Service):
The capability provided to the consumer is to deploy onto the cloud infrastructure consumer created or acquired applications created using programming languages and tools supported by the provider.
The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly application hosting environment configurations

SaaS(Software as a Service):
The capability provided to the consumer is to use the provider's applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., webbased email).
The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user specific application configuration settings

RULE 4 - Deployment models:
Private Cloud (Single Org)
The cloud infrastructure is operated solely for a single organization. It may be managed by the
organization or a third party, and may exist on-premises or off-premises, Also called as “Enterprise Cloud”

Community Cloud (Multiple Org)
The cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, or compliance considerations).
It may be managed by the organizations or a third party and may exist on-premises or off premises.
Public Cloud (For Public)
The cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services, Also called as “Internet Cloud”

Hybrid Cloud
The cloud infrastructure is a composition of two or more clouds (private, community, or public)
Leasing public cloud services when private cloud capacity is insufficient, Also called as “Mixed Cloud”

RULE 5 - Characteristics:
On-demand self-service:
Users can provision servers and networks with little human intervention.

Broad network access:
Any computing capabilities are available over the network. Many different devices are allowed access through standardized mechanisms.

Resource pooling:
Multiple users can access clouds that serve other consumers according to demand.
Cloud services need to share resources between users and clients in order to reduce costs.

Elasticity:
Provisioning is rapid and scales out or in based on need.

Metered or measured service:
One of the compelling business use cases for cloud computing is the ability to "pay as you go“, where the consumer pays only for the resources that are actually used by his applications.

Note: We have tried solving the question paper in a very short time span as per our understanding and the study material we had. Feel free to contact us through comment box or through email if you have some descriptive answer.



Question) 
Answer)
In a wide SCSI, the device IDs from 8 to 15 have the highest priority, but the entire sequence of wide SCSI-IDs has lower priority than narrow SCSI IDs.

Therefore, the overall priority sequence for a wide SCSI is 7, 6, 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, and 8.

Question) Firewall configuration is difficult for which NFS version? Justify.
Answer)
NFS is a client server protocol that allows users to share files across a network. There are some problems with NFS as stated below:
● NFS relies on the inherently insecure UDP protocol
● Transactions between host and client are NOT encrypted
● Hosts and users cannot be easily authenticated, IP Spoofing is possible
● Persmissions are granted by normal access rules
● Firewall configuration is difficult because of the way NFS daemons work

NFSv3 requires dynamic ports between the NFS server and client which can cause problems getting through your firewall.

Question)
What are the three types of nodes maintained by JFFS2? Mention percentage hit by ‘Garbage Collector’ to reclaims space from various types of nodes.
Answer)
JFFS is a log structured file system, Nodes containing data and metadata are stored on the flash chips sequentially. There are three types of nodes defined and implemented by JFFS2. These are as follows:

1. JFFS2_NODETYPE_INODE - It contains all the inode metadata, as well as potentially a range of data belonging to the inode. However, it no longer contains a file name or the number of the parent inode.
2. JFFS2_NODETYPE_DIRENT - this node represents a directory entry, or a link to an inode. It contains the inode number of the directory in which the link is found, the name of the link and the inode number of the inode to which the link refers. 
3. JFFS2_NODETYPE_CLEANMARKER -- this node is written to a newly erased block to show that the erase operation has completed successfully and the block may safely be used for storage.

Garbage Collector (GC):
Samba is an open-source software suite that runs on Unix/Linux based platforms but is able to communicate with Windows clients like a native application. So Samba is able to provide this service by employing the Common Internet File System (CIFS).

Can we install on windows ? - No we can not install it on Windows. Samba can be run on many different platforms including Linux, Unix, OpenVMS and operating systems other than Windows and allows the user to interact with a Windows client or server natively. It can basically be described as the Standard Windows interoperability suite of programs for Linux and Unix.

Name of file to configure SAMBA: smb.conf

Question )
In a SCSI based interface, a target has to support multiple initiators. Explain how a target will handle an incoming read request when it is busy, giving complete steps of read request between such initiator and a target components (handling multiple imitators) of a SCSI interface. Clearly indicate any assumptions made.

Answer)
Assumptions :Let us assume we have one target T1 and three initiators I1, I2 and I3 with below SCSI IDs :

Initiator  SCSI ID
I1              6
I2              3
I3              5

The device with SCSI ID 7 has the highest priority on the SCSI bus and is usually assigned to the host adapter. The priority of other SCSI IDs is descending from 6 to 0.

Phases of SCSI bus :
There are basically 3 phases :
•Bus Free Phase
–Bus is not being used by anyone

•Arbitration Phase
–One or more initiators request use of the bus and
the one with the highest priority (SCSI ID order) is allowed to proceed

•Selection / Re-selection phase
–Initiator asserts BUS BUSY signal and
•places target’s address on the bus thus establishing a connection/session
–Re-selection applies for a target resuming an interrupted operation:
•target asserts BUS BUSY signal and places initiator’s address on the bus.

Steps for Bus Phase Sequence Read Operation

Mid-Sem Paper Solutions:

Mid-Sem Paper Solutions:



Question:
Q.1 Choose the most appropriate architectural pattern (one) for the 5 descriptions below. Give reasons for choosing the pattern (in 1-2 line maximum)

• Wants a system that quickly can analyze enormous volumes of data by sorting the data and then analyzing the grouped data. -> Map-Reduce
• Wants to set up a set of equal distributed computational entities that are connected via a common protocol to share their services and provide high availability and scalability. -> Peer-to-peer

Answer:

Question:
Give an example for each of the following preprocessing activates
a. Incomplete
b. Inconsistent

Answer:
Data Processing: It is a data mining technique that involves transforming raw data into an understandable format. Our Real-world data is often incomplete, inconsistent, and/or lacking in certain behaviors or trends, and is likely to contain many errors. Hence it is needed for resolving such issues.
"Preprocessing is needed to improve data quality"

A. Incomplete: Lacking attribute values, lacking certain attributes of interest, or containing only aggregate data.
E.g. Many tuples have no recorded value for several attributes,
Occupation = “ ” (missing data)

B. Inconsistent: Containing discrepancies in codes or names.
E.g.
Age = “42”, Birthday = “03/07/2010”
Was rating “1, 2, 3”, now rating “A, B, C”
discrepancy between duplicate records

Question
One of your friends has written a program to search a string in a string and requested you to test the below function using equivalent class portioning :

function strpos_generic( $haystack, $needle, $nth,  $insensitive)
Following are terminology definitions:

• $haystack= the string in which you need to search value
• $needle= the character that needs to be searched, the $needle should be a single character
• $nth= occurrence you want to find, the value can be number between 1,2,3
• $insensitive= 1- case insensitive, 0 or any other value is case sensitive
• Passing as Null as parameter in haystack or needle is not a valid scenario and will return boolean false
• The function will return mixed integer either the position of the $nth occurrence of $needle in $haystack, or Boolean false if it can't be found.

a) Derive positive and negative domain equivalence class portioning with the value in the following format     

$haystack	$needle	$nth	$insensitive

                                                                             
b) And drive test case for weak robust variant in following format and use the variable efficiently and cover  all the paths:
 

Sl.no

$haystack

$needle

$nth

$insensitive

Expected  results

Answer:
NOTE : The above question is for your exercise,kindly try solving it using below reference questions

Question
ABC Transportation Company has implemented an online ticket booking system for their buses, and they have created a simple screen to search the bus and following are some of the business rules they have incorporated in the screen.
From and To location should be minimum 3 characters and maximum  of  25 characters
• Date of travel cannot be lesser than today’s date
• Time : Morning, Afternoon, Night
• No of Passengers can be 1 to 6
• Service class can be: Premium, Deluxe, Express
a) Identify the positive and negative domain.
b) Write test case for weak robust variant.

Question 1A)
The time factor when determining the efficiency of algorithm is measured by
a) Counting microseconds
b) Counting the number of key operations
c) Counting the number of statements
d) Counting the kilobytes of algorithm

Answer: b
Justification: It is hardware and language independent , rest are dependent on hardware or on software

1B) The concept of order Big O is important because
a) It can be used to decide the best algorithm that solves a given problem
b) It determines the maximum size of a problem that can be solved in a given  amount of time
c) It is the lower bound of the growth rate of algorithm
d) Both A and B

Answer: a
Justification: We know that Big Oh notation is used in time complexity . the reason why we called Big Oh because it says "at any condition this is worst time that an algorithm could take " where as Big Omega says its is "best time that you can get , You cant get better than this.

1C) In worst case Quick Sort has order
A) O (n log n)            B. O (n² /2)                C. O (log n)                         D. O (n² /4)

Answer: A
Justification: In the worst case of quick sort has order O(n2). Quick sort is the quickest comparison-based sorting algorithm. It is very fast and requires less additional space, only O(n log n) space is required.

1D) Consider the following program segment. What is the Space complexity?
Begin
i=0;
S=0;
S=s+1;
Return s;
End

Answer: [If i,S considered as integers] => Space Complexity = 4 +(4*2)  = 12 bytes, where additional 4 bytes is for return value

To calculate the Space complexity of an algorithm, we need to follow the below instruction first:

Space Complexity = Auxiliary Space + Input space

Calculating the Space Complexity:

Type	Size
bool, char, unsigned char, signed char	1 byte
short, unsigned short,	2 bytes
float, int, unsigned int, long, unsigned long	4 bytes
double, long double, long long	8 bytes

1E)  What is the time complexity of optimal binary search
(1) a)O(n) b) O(1) c)O(2^n/2)  d) O(n²)

Answer: d
Justification:
An optimal binary search tree is a binary search tree for which the nodes are arranged on levels such that the tree cost is minimum.

For Reference:
The complexity of linear search algorithm is
a) O(n)
b) O(log n)
c) O(n²)
d) O(n log n)

Answer: a
Justification: It refers to n values complexity in the algorithm which can be reduced by choosing the other algorithms.

The complexity of Bubble sort algorithm is
a) O(n)
b) O(log n)
c) O(n²)
d) O(n log n)

Answer: c
Justification: Bubble sort, is a simple sorting algorithm that works by repeatedly stepping through the list to be sorted, comparing each pair of adjacent items and swapping them if they are in the wrong order.

Question
Randomised algorithms are also called as __________________ and whose behavior is dependent  on  _______________ in decision making as part of its logic