What is Tunneling (VPN)?

Virtual Private Networks creates a tunnel for using a public network (such as Internet) to transfer information between client's PC and office's network. To initiate tunnel in client PC it must have VPN software to connect the ISP router (RAS). After verification of validity of user, software establishes the connection between ISP and use client machine. 

What is Network Security Threats?

• Computer Security means to protect information. It deals with prevention and detection of unauthorized actions by users of a computer.

In simple words security is defined as "Protecting information system from unintended access"

What is Network Security? Explain Basic Requirements of Network Security.

Network security is a broad topic with multilayered approach. It can be addressed at the data link layer, network layer and application layer. The issues concerned are: packet intrusion and encryption, IP packets and routing tables with their update version, and host-level bugs occurred at data link layer, network layer and application, respectively.

Explain Types of Firewall Architectures

Internet provides a two-way flow of traffic that may be undesirable in many organizations where some information may concern exclusively within the organization or for Intranet. Intranet is aTCP/IP network that is modeled after the Internet that only works within the organization. In order to delineate information meant only for the benefit of the organization or its Intranet and the other open to all or meant for Internet, some sorts of security measures need to be employed to control two-way flow of traffic. The measure known, as firewall is simply used for this purpose.

What is Firewall?

A firewall is a device installed between the internet network of an organization and the rest of Internet. When a computer is connected to Internet, it can create many problems for corporate companies. Most companies put a large amount of confidential information online. Such an information should not be disclosed to the unauthorized persons. Second problem is that the virus, worms and other digital pests can breach the security and can destroy the valuable data.

Types of Servers

File servers. -With a file server, the Computer Network client passes requests for computer network files or file records over a computer network to the file server. This form of computer network data service requires large bandwidth and can slow a computer network with many users down considerably. Traditional LAN (Local area Network) computing allows users to share resources, such as data files and peripheral devices, by moving them from standalone PCUs onto a Networked File Server (NFS).

What is packet

A packet is the unit of data that is routed between an origin of  computer  network and a destination of computer network on the Internet or any other packet-switched computer network. When any file (e-mail message, HTML file, Graphics Interchange Format file, Uniform Resource Locator request, and so forth) is sent from one place of computer network to another place of computer network on the Internet, the Transmission Control Protocol (TCP) layer of TCP/IP of computer network.

What is Switching? What is Network Switch?

Switching: Every time in computer network you access the internet or another  computer network outside your immediate location, your messages are sent through a maze of transmission media and connection devices. The mechanism for moving information between different computer network and network segment is called switching in computer network.

What is Router

Router: Routers are devices (computers) containing software that help in determining the best path out of the available paths, for a particular transmission. They consist of a combination of hardware and software. The hardware includes the physical interfaces to the various networks in the internet work. The two main pieces of software in a router are the operating system and the routing protocol.

What is a Modem? Types of Modems

Modem is abbreviation for Modulator – Demodulator. Modems are used for data transfer from one computer network to another computer network through telephone lines. The computer network works in digital mode, while analog technology is used for carrying massages across phone lines.

MAC Address - What do you understand by MAC address?

In a local area network (LAN) or other network, the MAC (Media Access Control) address is your computer's unique hardware number. (On an Ethernet LAN, it's the same as your Ethernet address.)

SubNetting - What is Subnetting?

The process of subnetting involves dividing a network up into smaller networks called subnets or sub networks. Each of these subnets has its own specific address. To create these additional networks we use a subnet mask. The subnet mask simply determines which portion of the IP address belongs to the host. The subnet address is created by dividing the host address into network address and host address.

Public IP Address - What Is a Public IP Address?ARP

An IP address is considered public if the IP number is valid and falls outside any of the IP address ranges reserved for private uses by Internet standards group. Public IP addresses are used by servers (including those for Web sites and DNS servers), network routers or any computer connected directly to the Internet via a modem.

IP Address Classes or Classful addressing

• IP addressing supports five different address classes: A, B, C, D and E. Only classes A, Band C are available for commercial use.

• We can find the class of an address when given the address in binary notation or dotted decimal notation.

What is IP (Internet Protocol)? IPV4 & IPV6 (Internet Protocol Versions)

In order to provide computer to computer communication via Internet, we need a global addressing scheme. Such an addressing is provided by Internet Protocol (IP) at the network layer.

JDBC operations - SELECT, INSERT, UPDATE, DELETE

• How to insert new records/rows in database tables (INSERT operation)
• How to find a record/row in database tables (SELECT operation)
• How to update records/rows in tables (UPDATE operation)
• How to delete a record/row from tables (DELETE operation)

Implementation of 0/1 Knapsack problem using Dynamic Programming in Java

What is 0/1 Knapsack problem ?The knapsack or rucksack problem is a problem in combinatorial optimization. Here there are a set of items(n) which has a profit value(v) and weight(w). 

SQL Interview Questions

SQL Queries Interview Questions - Oracle Part 1

As a database developer, writing SQL queries, PLSQL code is part of daily life. Having a good knowledge on SQL is really important. Here i am posting some practical examples on SQL queries.

To solve these interview questions on SQL queries you have to create the products, sales tables in your oracle database. The "Create Table", "Insert" statements are provided below.

SQL Queries

1.     To fetch ALTERNATE records from a table. (EVEN NUMBERED)
select * from emp where rowid in (select decode(mod(rownum,2),0,rowid, null) from emp);

2.     To select ALTERNATE records from a table. (ODD NUMBERED)
select * from emp where rowid in (select decode(mod(rownum,2),0,null ,rowid) from emp);

3.     Find the 3rd MAX salary in the emp table.
select distinct sal from emp e1 where 3 = (select count(distinct sal) from emp e2 where e1.sal <= e2.sal);

4.     Find the 3rd MIN salary in the emp table.
select distinct sal from emp e1 where 3 = (select count(distinct sal) from emp e2where e1.sal >= e2.sal);

5.     Select FIRST n records from a table.
select * from emp where rownum<= &n;

Informatica Important Questions?

What are the differences between Connected and Unconnected Lookup?

The differences are illustrated in the below table

Connected Lookup	Unconnected Lookup
Connected lookup participates in dataflow and receives input directly from the pipeline	Unconnected lookup receives input values from the result of a LKP: expression in another transformation
Connected lookup can use both dynamic and static cache	Unconnected Lookup cache can NOT be dynamic
Connected lookup can return more than one column value ( output port )	Unconnected Lookup can return only one column value i.e. output port
Connected lookup caches all lookup columns	Unconnected lookup caches only the lookup output ports in the lookup conditions and the return port
Supports user-defined default values (i.e. value to return when lookup conditions are not satisfied)	Does not support user defined default values

Power Exchange, Power Center, Power mart

PowerCenter===========PowerCenter can have many repositories. It supports the Global Repository and networked local repositories.PowerCenter can connect to all native legacy source systems such as Mainframe, ERP, CRM, EAI (TIBCO, MSMQ, JMQ) High Availability and Load sharing on multiple servers in the grid.Informatica Session level Partioning is available.Informatica Pushdown Optimizer is available.