Online Programz

Traditional dial-up Internet services are sometimes referred to as “dial-on-demand” services. That is, your computer only connects to the Internet when it has something to send, such as email or a request to load a web page. Once there is no more data to be sent, or after a certain amount of idle time, the computer disconnects the call. Also, in most cases each call connects to a pool of modems at the ISP, and since the modem IP addresses are dynamically assigned, your computer is usually assigned a different IP address on each call. As a result, it is more difficult (not impossible, just difficult) for an attacker to take advantage of vulnerable network services to take control of your computer.

Broadband services are referred to as “always-on” services because there is no call setup when your computer has something to send. The computer is always on the network, ready to send or receive data through its network interface card (NIC). Since the connection is always up, your computer’s IP address will change less frequently (if at all), thus making it more of a fixed target for attack.

What’s more, many broadband service providers use well-known IP addresses for home users. So while an attacker may not be able to single out your specific computer as belonging to you, they may at least be able to know that your service providers’ broadband customers are within a certain address range, thereby making your computer a more likely target than it might have been otherwise.

Social network analysis, which is related to Network Theory, has emerged as a tool to understand how social networks work. Social networks have been studied for quite a while, in fields ranging from modern sociology, anthropology, social psychology, communication studies, information science, organizational studies as well as Biology (Van Den Bulte and Wuyts 2007).

A social network is a social structure made of nodes (which are generally individuals or organizations) that are tied by one or more specific types of interdependency, such as values, visions, ideas, financial exchange, friendship, kinship, dislike, conflict or trade. The resulting structures are often very complex, after all human nature is inherently complex.
The question of how the pattern of interconnection among social entities – consumers, colleagues, business units, competitors and complementors – affect behaviours and the outcomes of those entities in now receiving more attention than ever (Van Den Bulte and Wuyts 2007).

Social network analysis views social relationships in terms of nodes and ties, as basic building blocks. Nodes are the individual actors within the networks, and ties are the relationships between the actors. There can be many kinds of ties between the nodes. Research in a number of academic fields has shown that social networks operate on many levels, from families up to the level of nations, and play a critical role in determining the way problems are solved, organizations are run, and the degree to which individuals succeed in achieving their goals.
In its simplest form, a social network is a map of all of the relevant ties between the nodes being studied. The network can also be used to determine the social capital of individual actors. These concepts are often displayed in a social network diagram, where nodes are the points and ties are the lines.

At its heart, a network is simply a way of connecting two or more computers together. At the base level this allows the exchange of information between computers, but this in turn leads to bigger things — sharing of documents, files, gaming, media streaming and more.

These days a network often involves more than just computers; it can also include devices such as phones, game consoles and MP3 players thanks to the growing importance of the internet in our lives. Think of the internet as one giant network (or more correctly, a series of interconnected networks) — so when you get online, you’re becoming part of that huge network.

Network Security Concepts is start from authenticating users,

Commonly (one-factor authentication) with a username and a password.

With two-factor authentication something you always used in your daily life (e.g. a security token or ‘dongle’, an ATM card, or your mobile phone, login computers ),

or with Three-factor authentication as an additional security features that some of us also used (e.g. a fingerprint or retinal scan).

Once authenticated, a stateful firewall will enforce the access policies such as what services
are allowed to be accessed by the network users. This is effective to prevent unauthorized access, this component can’t check potentially harmful content such as computer worms being transmitted over the network.

Routing refers to the process of choosing a path over which to send packets. The information used to make routing decisions is known as IP routing information. Routing Software would examine network load, Datagram length or type of service specified in the datagram header when selecting the best path. An internet composed of multiple physical networks interconnected by computers is called routers. Both host and routers participate in routing an IP datagram protocol to its destination. The purpose of routers is to make IP routing decisions. There are two forms of IP routing. Direct delivery and Indirect delivery.

Direct Delivery :

The transmission of IP Datagram from one machine across a single physical network directly to another.

Indirect delivery :

When the destination is not on a directly attached network it forces the sender to pass the IP datagram to a router for delivery.

JDBC stands for database connectivity. JDBC is a sql level API that allows to execute SQL statement and retrieve results if any.

Two & Three Tier Databse Access Models :

The JDBC provides support for both two and three tier database access models.

Two Tier Model :

The java application lacks direct communication to the database. Hence it communicates directly to database and the results of these are then sent from database back to application.

Three Tier Model :

In Three tier model, the JDBC driver send commands to middle tier, which is then send commands to the database. The results are sent back to the middle tier which communicates them back to the application.

Advantage :

They have direct interface with database .

Disadvantage:

A defect in a driver’s native code section can crash the entire server.

Function Of  E-Mail Systems :

Typically e-mail systems support five basic function namely.

• Composition : Process of creating messages and answers.
• Transfer : Process of moving message from the originator to the recipient.
• Reporting : Process of telling the originator whether the message has been delivered or rejected or lost.
• Displaying : The process of representing the incoming message so that people can read this mail.
• Disposition: Concerned with what the recipient does with the message after receiving it.

Structure Of E-Mail :

E-mail has the distinction between envelope and its contents.

Envelope :

Envelope encapsulates the message containing all the information needed for transporting the message such as destination address priority, security level.

Message Or Content:

The message include the envelope consists of two parts

• header : information for user agents.

• body : information for human recipient.

Sockets are an extension of one of Unix’s most important ideas. They are an innovation of Berkeley Unix that allows programmer to treat a connection in network as another stream onto which bytes can be written to and from which bytes can be read.

Socket basics:

Definition : A socket is a connection between two hosts.

Operations:

A socket can perform the following operations.

• Connect to a remote machine.
• Send data.
• Receive data.
• Close a machine.
• Bind a port.
• Listening for information data.
• Accept connections from remote machines on bound port.

Sockets client are simply called as sockets and sockets for server side are called as server socket. Hence for client side socket class is being used and for server side.Server socket class is being used.

Internet Address :

Devices connected to the internet are called nodes. Nodes that are computers are called hosts. Each node or hosts is identified by at least one unique 32 bit numbers called Internet address.

Internet address is written as four unsigned bytes, each ranging from 0 to 255. Bytes are separated by periods.

DNS :

DNS stands for Domain Name system which associates host names that human can remember easily.

Example :

152.2.21.1 is associated with domain name such as oit unc.edu.

Inet Address Class:

Inet Address class is an encapsulation of IP address. It can be used by other classes like socket, server socket, URL, Datagram Socket, Datagram Packet and more.

Function:

Inet Address can be specified as two fields

Host name – String _ contains names of the host.

Address- integer- contains 32 bit IP address.

The method of this class can’t be called directly

Stream:

A stream is a an abstraction that either produces or consumes information. A stream is linked to a physical device by the java I/O stream.

Types Of Stream:

• Byte Stream
• Character Stream

Byte Stream :

• Handles input and output of bytes.
• Classes: Input Stream and Output Stream (important classes)
• Methods: read(), write() (important methods)

Character Stream:

• Handles input and output of characters
• Classes: Reader and Writer (important classes)
• Methods: read() and write() (important methods)