Concepts of Network

User

• Single user: It is most commonly used when talking about an operating system being usable only by one person at a time, or in reference to a single-user software license agreement. Eg DOS

• Multi-user: It is a term that defines an operating system or application software that allows simultaneous access by multiple users of a computer. Time-sharing systems are multi-user systems. It avoid leaving the CPU idle while it waits for I/O operations to complete Eg Linux, unix

Workstation• It refers to a computer that has been configured to perform a certain set of

tasks, such as photo editing, audio recording, or video production. An office may have several workstations for different purposes, which may be assigned to certain employees. For example, one workstation may be used for scanning and importing images, while another is used for editing images.

Because workstations often work together like in the example above, they are commonly networked together. This allows them to send files back and forth over the network, which is important for various types of media production. To use another example, a user at a photo-editing workstation may prepare images to be used in a video clip. Once the images are ready, he may send them to another user at a video-editing workstation, where they are incorporated into the video. Once the video has been put together, the video file may be sent to another user at an audio production workstation where the soundtrack and other sound effects are added.

While workstations are often part of a network, they can be standalone machines as well. Historically, workstations had offered higher performance than personal computers, especially with respect to CPU and graphics, memory capacity .

Servers

• A server is a a software program, or the computer on which that program runs, that provides a specific kind of service to client software running on the same computer or other computers on a network.

• A server serves information to computers that connect to it. When users connect to a server, they can access programs, files, and other information from the server. Common servers are Web servers, mail servers, and LAN servers. A single computer can have several different server programs running on it.

LAN

• LAN: Stands for "Local Area Network," .A LAN is a computer network limited to a small area such as an office building, university, or even a residential home. Most mid to large-sized businesses today use LANs, which makes it easy for employees to share information. Currently, the most common type of LANs are Ethernet-based. However, with the emergence of wireless networking, wireless LANs have become a popular alternative.

MAN

• A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network.

• Examples of metropolitan area networks of various sizes can be found in the metropolitan areas of London, England; and Geneva, Switzerland.

WAN

• Stands for "Wide Area Network." It is similar to a Local Area Network (LAN), but it's a lot bigger. Unlike LANs, WANs are not limited to a single location. Many wide area networks span long distances via telephone lines, fiber-optic cables, or satellite links. They can also be composed of smaller LANs that are interconnected. The Internet could be described as the biggest WAN in the world.

IP• Also known as an "IP number" or simply an "IP," this is a code

made up of numbers separated by three dots that identifies a particular computer on the Internet. Every computer, whether it be a Web server or the computer, requires an IP address to connect to the Internet. IP addresses consist of four sets of numbers from 0 to 255, separated by three dots. For example "66.72.98.236" or "216.239.115.148". Your Internet Service Provider (ISP), will assign you either a static IP address (which is always the same) or a dynamic IP address, (which changes every time you log on). ISPs typically assign dial-up users a dynamic IP address each time they sign on because it reduces the number of IP addresses they must register. However, if you connect to the Internet through a network or broadband connection, it is more likely that you have a static IP address

IP types

• Class A - This class is for very large networks, such as a major international company might have.

• Network host

• 0xxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx

• IP addresses with a first octet from 1 to 126 are part of this class.

Class B - Class B is used for medium-sized networks. A good example is a large college campus. IP addresses with a first octet from 128 to 191 are part of this class.

• Net Host or Node

• 145.24. 53.107

• 10xxxxxx.xxxxxxxx xxxxxxxx.xxxxxxxx

• Class C - Class C addresses are commonly used for small to mid-size businesses.

• 110xxxxx.xxxxxxx xxxxxxxx.xxxxxxxx

• Class D - Used for multicasts.

• 1110xxxx.

• Class E - Class E is used for experimental purposes only.

Host

• This is a computer that acts as a server for other computers on a network. It can be a Web server, an e-mail server, an FTP server, etc. For example, a Web host is what provides the content of Web pages to the computers that access it.

Remote machine

• A remote computer is a computer to which a user does not have physical access, but which he or she can access/manipulate via some kind of network.

How does DNS service work?• DNS stands for "Domain Name System." The primary purpose of DNS is to keep Web

surfers sane. Without DNS, we would have to remember the IP address of every site we wanted to visit, instead of just the domain name. A domain is nothing but a name or a string of words that corresponds to a certain IP address for instance www.apple.com. Can you imagine having to remember "17.254.3.183" instead of just "apple.com"? The reason the Domain Name System is used is because Web sites are actually located by their IP addresses. For example, when you type in "http://www.adobe.com," the computer doesn't immediately know that it should look for Adobe's Web site. Instead, it sends a request to the nearest DNS server, which finds the correct IP address for "adobe.com." Your computer then attempts to connect to the server with that IP number.

• DNS servers are as following :• Primary DNS Server: It contains a database of all hostname and their corresponding

IP addresses for the domain.• Secondary DNS Server: Each domain have at least one secondary server for

redundancy purpose.• Caching-only DNS Server: It remember the answer for query for a period of time. If

same query is make by any client in that time period, it gives the answer stored in cache, instead of forwarding.