Server Types

This list, courtesy of serverwatch.com, categorizes the many different
types of servers used in the marketplace today. Click on the server
category you'd like to know more about, and you will be taken directly
to a serverwatch.com page that provides additional information and
resources.

Server Platforms
A term often used synonymously with operating system, a platform is
the underlying hardware or software for a system and is thus the
engine that drives the server.
Application Servers
Sometimes referred to as a type of middleware, application servers
occupy a large chunk of computing territory between database servers
and the end user, and they often connect the two.
Audio/Video Servers
Audio/Video servers bring multimedia capabilities to Web sites by
enabling them to broadcast streaming multimedia content.
Chat Servers
Chat servers enable a large number of users to exchange information in
an environment similar to Internet newsgroups that offer real-time
discussion capabilities.
Fax Servers
A fax server is an ideal solution for organizations looking to reduce
incoming and outgoing telephone resources but that need to fax actual
documents.
FTP Servers
One of the oldest of the Internet services, File Transfer Protocol
makes it possible to move one or more files securely between computers
while providing file security and organization as well as transfer
control.
Groupware Servers
A groupware server is software designed to enable users to
collaborate, regardless of location, via the Internet or a corporate
intranet and to work together in a virtual atmosphere.
IRC Servers
An option for those seeking real-time discussion capabilities,
Internet Relay Chat consists of various separate networks (or "nets")
of servers that allow users to connect to each other via an IRC
network.
List Servers
List servers offer a way to better manage mailing lists, whether they
be interactive discussions open to the public or one-way lists that
deliver announcements, newsletters, or advertising.
Mail Servers
Almost as ubiquitous and crucial as Web servers, mail servers move and
store mail over corporate networks (via LANs and WANs) and across the
Internet.
News Servers
News servers act as a distribution and delivery source for the
thousands of public news groups currently accessible over the USENET
news network.
Proxy Servers
Proxy servers sit between a client program (typically a Web browser)
and an external server (typically another server on the Web) to filter
requests, improve performance, and share connections.
Telnet Servers
A Telnet server enables users to log on to a host computer and perform
tasks as if they're working on the remote computer itself.
Web Servers
At its core, a Web server serves static content to a Web browser by
loading a file from a disk and serving it across the network to a
user's Web browser. This entire exchange is mediated by the browser
and server talking to each other using HTTP. Also read ServerWatch's
Web Server Basics article.

Getting started with IMAP for Gmail

Getting started with IMAP for Gmail

What is IMAP?

IMAP, or Internet Message Access Protocol, lets you download messages from Gmail's servers onto your computer so you can access your mail with a program like Microsoft Outlook Express or Apple Mail, even when you aren't connected to the Internet.

IMAP creates a constant connection between mail clients (desktop and/or mobile) and Gmail.

What's the difference between IMAP and POP?

Unlike POP, IMAP offers two-way communication between your web Gmail and your email client(s). This means when you log in to Gmail using a web browser, actions you perform on email clients and mobile devices (ex: putting mail in a 'work' folder) will instantly and automatically appear in Gmail (ex: it will already have a 'work' label on that email).

In addition, IMAP provides a better method to access your mail from multiple devices. If you check your email at work, on your mobile phone, and again at home, IMAP ensures that new mail is accessible from any device at any given time.

Finally, IMAP offers a more stable experience overall. Whereas POP is prone to losing messages or downloading the same messages multiple times, IMAP avoids this through its two-way syncing capabilities between your mail clients and your web Gmail.

If you're trying to decide between using POP and using IMAP with Gmail, we recommend IMAP.

How much does IMAP cost?

IMAP for Gmail is free.

Great! How do I get started?

First, you'll need to enable IMAP in Gmail. Once IMAP is enabled, follow the configuration instructions for your client of choice. Currently, only the clients listed are supported for IMAP. If you'd like to download your Gmail messages with a different client, please check to see if it's on our list of supported POP clients.

When you've enabled IMAP and set up your client, sign in to Gmail through the client and watch your messages arrive. You'll notice that all of your custom Gmail labels will appear in your client as folders, with copies of the messages to which you've applied those labels. While we'd like to make your IMAP experience match the Gmail web interface as much as possible, some Gmail-specific features and terms, such as conversation threading and stars, won't appear in your client. Don't worry; you can still perform all the usual Gmail functions, just in a slightly different way. The IMAP behavior chart shows you how to perform common functions on your IMAP client.

Please note that every client handles IMAP in a slightly different way. If you're curious about the specific use of your client, please contact the client's support team.

Internet and Computer Security

Internet

In a nutshell, the Internet is a whole bunch of cables running around the entire globe, connecting millions of computers to each other. Technically, it is called a Wide Area Network, or WAN. The Internet is often described as ‘a network of networks’ because all the smaller networks of organizations are linked together into a giant network called Internet. It is a conglomeration of thousands of computer networks using a common set of protocols to create a worldwide communication medium.

Origin of Internet

In 1970s, there was a project called APRANET (Advanced Research Projects Agency Network) by US department of Defense called Advanced Research Projects Agency (APRA). This project was design a network service for computer communications on over wide area.

OSI Reference Model Internet Protocol suite

FTP, Telnet SMTP, SNMP	NFS
	XDR
	RPC
TCP, UDP
IP
ARP, RARP
NOT SPECIFIED

Application

Presentation

Session

Transport

Network

Data Link

Physical

Physical: Transform raw transmission into data frames and transmit the frames sequentially.

Network: Controls the operation of the network like routing of the packets to the destination.

Transport: Takes care of splitting of data into units, if required and ensures correct delivery if these units on other side.

Session: Supports sessions between users on different machines. Also supports remote logins and file sharing between systems.

Presentation: Takes care of syntax and semantics of the information transmitted.

Application: Contains a collection of protocols is that are commonly needed for application.

Conceptual overview of Internet

There are four basics types of entities on the Internet.

1) End users

2) Internet service providers.

3) Backbone providers and

4) Network Access point (NAP) operators.

End users access and send information either through the individual connections or through organizations. Internet service providers connect those end user to Internet backbone networks .The Backbone providers route data between ISPs and interconnect with other backbone providers. NAP operators maintain public peering points on the Internet through which data is routed between the major backbone providers. The NAP’s are equipped to handle large amounts of data to avoid bottlenecks.

Some ISPs are: BSNL, Satyam online.

Types of Internet access

Single user Access: This uses a Standard Computer, a Modem, a Telephone line, an Internet Account and few extra things such as Web Browser software and E-mail software may be required.

Multi User Access: Multi user Access means that two or more people can access the Internet from different computers at same time. This involves setting the computers that are at different points in the organization into Local Area Network (LAN). Once set up into LAN a router can be used to provide multiple accesses.

Types of accounts

Shell account: The shell account is UNIX based on a service provider’s computer. Using a shell account is usually a time consuming and monotonous task. A shell account will not support any of the Graphical browsers. When using a shell account the user is transported to the remote computer (the service provides computer), which is on the Internet. These accounts provide the user with a dial- in service to access providers network.

TCP/IP account: A TCP/IP account places the users machine directly on the Internet.

Internet tools & applications

Benefits of the Internet for Business: The usefulness of the Internet depends directly on the products and services of each business.

E-mail: Electronic mail is a messaging system, which allows you to send/receive messages and reports to/from user on the Internet. Some advantages of E-mail are

1.speed 2.cost effectiveness 3.audio and video clips

Features of E-mail:

1. Compose 2.Receive and Reply 3.Copies

4. Forward 5.Folders 6.Vacaion Replies.

7. Attach Signatures 8.Attach visiting Cards 9.Address Books.

10. Greetings 11.Filter Mails.

Mailing lists: Mailing lists are extension of E-mail. When you want to send information about a product should send messages to all your customers. Instead of typing all their address in the recipients address field you can create a mailing list with all these addresses called “customers”. Then when you send a message to this list it will send to all the customers.

Internet Newsgroup: Internet Newsgroup is a system to public worldwide conferencing and discussions somewhat in the manner of an electronic bulletin board. Internet Relay chat (IRC): IRC is a multi user chat system where people meet on channels to talk in groups or privately. There is no restriction to the number of people that can participate in a given discussion or the number of channels that can be formed on IRC. IRC uses a streaming technology that provides fast response how fast you type is how fast your messages are up.

Browsers: It provides a user interactive interface and a lot of functions that may customize the browser, as you like.

Secured Browsing:

Types of security Zones

Zone Level of Security

Local Intranet Medium (prompt)

Trusted sites Low (Accept)

Internet Zone Medium (prompt)

Restricted Sites Zone High (Reject)

Cookies: Cookies refer to information stored on system by a server for later reference.

Search Engine: They use automated software called web crawlers or spiders. These programs move from Website to Website, logging each site title, URL and at least some of its text content. The objective is to hit millions of websites and to stay as current with them as possible.

Gopher: Gopher is a networked information retrieval and publishing tool, based on concept if hierarchical menus. Gopher is a client/server system that allows the user to access many Internet resources simply by making selections from a sequence of menus. Gopher carries the request to the computer that contains information and server it up.

Archie: It is a public domain tool offering an electronic directory service for locating file in anonymous FTP sites.

Telnet: Telnet is the protocol used to establish a login session on a remote computer on the network. This will directly connect you to the machine you specify.

Ping: The ping command checks the connections of the remote machine with your computer. It just sends 64 bytes packets of data to a computer you specify and receive them back. Then it validates the received packet against the transmitted message. You can indicate the address of machine by its name or IP address. The ping will display the number of packets transmitted and time in which each packet is received.

Internet protocols

Internet protocol (IP): It is a network layer protocol that contained addressing information and some control information that enables packets to be routed. Along with TCP IP represents the heart of Internet protocols.

IP PACKET FORMAT

Version	IHL	Typed of Service	Total Length
Identification
Time to live		Protocol	Header check Sum
Source Address
Destination Address
Options (+ padding)
Data (Variable)

Address resolution protocol: The IP address what we assign to a computer is only logical and is assigned by network administrator. But each computer has unique physical address. This address is called MAC address corresponding to a particular IP network layer address.

Reverse address Resolution protocol: The RARP is used to map MAC layer address to IP Address. RARP is the logical inverse of ARP, might be used by diskless workstations that do not know their IP addresses when they boot.

TCP: The TCP provides reliable transmission of data in an IP environment. The major services provided by the TCP are stream data transfer, reliability, efficient flow control, full-duplex operation and multiplexing.

TCP PACKET FORMAT:

Source port	Destination port
Sequence numbers
Acknowledgement number
Data offset	Reserved	Flags	Window
Check sum			Urgent pointer
Options (+ padding)
Data (Variable)

User datagram protocol (UDP): The UDP is a connectionless transport layer protocol that belongs to the Internet protocol family. UDP is basically an interface between IP and upper layer process.

UDP Packet:

Source port	Destination port
Length	Check sum

Others Applications

Hypertext transport HTML

File Transfer FTP

Terminal emulation Telnet

Electronic mail SMTP

Networking management SNMP

Distributed File Services NFS, XDR, RPC, XWINDOWS

COMPUTER SECURITY

Securing the data stored in the computer without misusing is called Computer Security.

Aspects of security

Data Integrity: Integrity refers to protection of unauthorized persons.

Data Availability: Availability refers to protection against disrupt of service.

Data Confidentiality and privacy: Confidentiality and privacy refer to protection against snooping or wire-tapping.

The issue of responsibility for information has several aspects to consider:

Accountability: Accountability refers to how an audit trail is kept. Which group is responsible for each item at data? How does this group keep records of access and change?

Authorization: Authorization refers to responsibility for each item of information and how such responsibility is delegated to others. Who is responsible for where information resides and how does a responsible person approve access and change.

Integrity mechanism

The techniques used to ensure the integrity of data against accidental damage are

Parity bits, checksum, and cyclic redundancy checks (CRCS).

A check sum or CRC cannot absolutely guarantee data integrity for two reasons. First is malfunctioning hardware, changes the value of a checksum as well as the value of the data. It is possible for the altered checksum to be valid for the altered data. Second if data changes result from a planned attack. The attacker can create a valid checksum for the altered data. Several mechanisms have been used to guarantee the integrity of message against intentional change. In general the methods encode transmitted data with a message authentication code (MAC) that attacker cannot break or forge. Typical encoding schemes uses cryptographic hashing mechanisms.

Access control and passwords

Many computer systems use password mechanism to control access to resources. A simple password scheme works well for a conventional computer system because the system does not reveal the passwords to others. In a network however a simple password mechanism is susceptible to eves dropping. If a user at one location sends a password across the network to a computer at another location, any one who wiretaps the network can obtain a copy of password. Wire-tapping is especially easy when packets travel across a LAN because many LAN technologies permit an attached station to capture a copy of all traffic.

Encryption and privacy

To ensure that the content of a message remains confidential despite wire-tapping. The message must be encrypted. In essence encryption scrambles bits of the message in such a way that only the intended recipient can unscramble them.

Several technologies exist for encryption key. In some technologies a sender and receiver must both have a copy of an encrypted key. The sender uses the key to produce an encrypted message. The receiver uses the key to decode the encrypted message i.e. the encrypt function used by the sender takes two arguments a key ‘k’ and message ‘m’ to be encrypted.

The function produces an encrypted version of message, E

E=encrypt (k, m)

The decrypt function reverses the mapping to produce the original message

M=decrypt (K, E)

Mathematically decrypt is the inverse of encrypt

M=decrypt (k, encrypt (K, M))

Public key encryption

In many encryption schemes, the key must be kept secret to avoid compromising security. One particular interesting encryption technique assigns each user a pair of keys. One of the user keys called the private key is kept secret, while the other, called the public key, is published along with the name of the user. The encryption function has the mathematical property that a message encrypted with the public key cannot be easily decrypt except with private key and a message encrypted with the private key cannot be decrypted except with the public key.

Let M denotes a message, pub-u₁ denotes users public key and prv-ul denote user’s private key. Then

M=decrypt (pub-u₁, encrypt (prv-u₁, M))

And

M=decrypt (prv-u₁, encrypt (pub-u₁, M))

Public key encrypt encryption can be used to guarantee confidentiality. A sender who wishes a message to remain private uses the receiver’s public key to encrypt the message. The scheme ensures that data remains confidential because only the receiver can decrypt the message.

Authentication with digital signatures

An encryption mechanism can also be used to authenticate the sender of a message. The technique is known as digital signature. To sign a message the sender encrypts the message using a key known only to the sender. The recipient uses the inverse function to decrypt the message. The recipient knows who has sent the message because only the sender has the key needed to perform the encryption. To ensure the encrypted messages are not copied and resent later, the original message contains time and date that the message was created.

Consider how a public key system can be used to provide a digital signature. The message is signed by using the sender’s private key to encrypt it. Second the encrypted message is encrypted again using the recipient’s public key.

X=encrypt (pun-u₂, encrypt (prv-u₁, M))

The recipient uses his private key to decrypt the message and sender’s public key to decrypt the message again.

M=decrypt (pub-u₁, encrypt (prv-u₂, X))

Internet firewall concept

A packet filter is often used to protect an organizations computer and networks from unwanted Internet traffic.

packet filter configured to protect and organization against traffic from the rest of the Internet Fire wall

Firewalls are the most important security tool used to handle network connection between two organizations that do not trust each other. By placing a firewall on each external network connection, an organization can define a secure perimeter that prevents outsiders from interfering with the organizations computers.

In particular by limiting access to a small set at computers. A firewall can prevent outsiders from probing all computers in an organization. Flooding the organizations network with unwanted traffic or attacking a computer by sending a sequence of IP data grams i.e. known to cause the computer system to misbehave. A firewall can lower the cost of providing security

How To Uninstall/Remove Linux & run only Win XP

Hello everybody..

This is how you can delete/remove Linux from a dualboot system with Windows XP.

First take out your Windows XP bootable disc & boot your system from it. Then enter Recovery console by pressing R. In the recovery console prompt type the following commands:
FIXMBR
FIXBOOT

The GRUB will be overwritten & Windows will restore MBR & its bootloader. Just boot your system & windows will start automatically.

Now Right click on My Computer icon on your Desktop & click Manage. Click Disk Management.
Now remove all Linux partitions (These partitions don't have any label & have unknown filesystem).
Now create new partition(s) in the free space. Format those partitions in FAT32/NTFS & now you can use them under Windows.

the above method works only for those who r using both win & lnux (and r willing to remove linux)..