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Network Topology

چهارشنبه 14 اردیبهشت 1390   12:49 ب.ظ


نوع مطلب : Network + ،

Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer network.[1][2] Network topologies may be physical or logical. Physical topology means the physical design of a network including the devices, location and cable installation. Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network.

Topology can be considered as a virtual shape or structure of a network. This shape does not correspond to the actual physical design of the devices on the computer network. The computers on a home network can be arranged in a circle but it does not necessarily mean that it represents a ring topology.

Any particular network topology is determined only by the graphical mapping of the configuration of physical and/or logical connections between nodes. The study of network topology uses graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ in two networks and yet their topologies may be identical.

A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology. Any given node in the LAN has one or more links to one or more nodes in the network and the mapping of these links and nodes in a graph results in a geometric shape that may be used to describe the physical topology of the network. Likewise, the mapping of the data flow between the nodes in the network determines the logical topology of the network. The physical and logical topologies may or may not be identical in any particular network.


نوشته شده توسط : Hiva Eskandari Pour

what is the differences between Internet , Intranet And Extranet?

چهارشنبه 24 فروردین 1390   12:09 ب.ظ


نوع مطلب : Network + ،

Internet, Intranet ,and Extranet



There's one major distinction between an intranet and the Internet: The Internet is an open, public space, while an intranet is designed to be a private space. An intranet may be accessible from the Internet, but as a rule it's protected by a password and accessible only to employees or other authorized users.

From within a company, an intranet server may respond much more quickly than a typical Web site. This is because the public Internet is at the mercy of traffic spikes, server breakdowns and other problems that may slow the network. Within a company, however, users have much more bandwidth and network hardware may be more reliable. This makes it easier to serve high bandwidth content, such as audio and video, over an intranet.


(unless you work for the United States Marine Corps. Then you don't get to watch video's. And they Block 80% of any kind of "fun" or entertaining website available on the Internet)

The Extranet is a portion of an organization's Intranet that is made accessible to authorized outside users without full access to an entire organization's intranet.


نوشته شده توسط : Hiva Eskandari Pour

Different Types of Servers

سه شنبه 23 فروردین 1390   05:30 ب.ظ


نوع مطلب : Network + ،

A server has many functions, and they come in different types to facilitate different uses. Before knowing about the different types of servers, let's have a brief idea on what is a server.

What is a Server?
A server is a device with a particular set of programs or protocols that provide various services, which other machines or clients request, to perform certain tasks. Together, a server and its clients form a client/server network which provides routing systems and centralized access to information, resources, stored data, etc. At the most ground level, one can consider it as a technology solution that serves files, data, print, fax resources and multiple computers. The advanced server versions, like Windows Small Business Server 2003 R2 enable the user to handle the accounts and passwords, allow or limit the access to shared resources, automatically support the data and access the business information remotely. For example, a file server is a machine that maintains files and allows clients or users to upload and download files from it. Similarly, a web server hosts websites and allows users to access these websites. Clients mainly include computers, printers, faxes or other devices that can be connected to the server. By using a server, one can securely share files and resources like fax machines and printers. Hence, with a server network, employees can access the Internet or company e-mail simultaneously.

Different Types of Servers
The multiple types of servers or types of network servers are as follows:
  • Server Platform: Server platform is the fundamental hardware or software for a system which acts as an engine that drives the server. It is often used synonymously with an operating system.
  • Application Server: Also known as a type of middleware, it occupies a substantial amount of computing region between database servers and the end user, and is commonly used to connect the two.
  • Audio/Video Server: It provides multimedia capabilities to websites by helping the user to broadcast streaming multimedia content.
  • Chat Server: It serves the users to exchange data in an environment similar to Internet newsgroup which provides real time discussion capabilities.
  • Fax Server: It is one of the best option for organizations seeking for minimum incoming and outgoing telephone resources, but require to fax actual documents.
  • FTP Server: It works on one of the oldest of the Internet services, the file transfer protocol. It provides a secure file transfer between computers while ensuring file security and transfer control.
  • Groupware Server: It is a software designed that enables the users to work together, irrespective of the location, through the Internet or a corporate intranet and to function together in a virtual atmosphere.
  • IRC Server: It is an ideal option for those looking for real-time discussion capabilities. Internet Relay Chat comprises different network servers that enable the users to connect to each other through an IRC network.
  • List Server: It provides a better way of managing mailing lists. The server can be either open interactive discussion for the people or a one-way list that provide announcements, newsletters or advertising.
  • Mail Server: It transfers and stores mails over corporate networks through LANs, WANs and across the Internet.
  • News Server: It serves as a distribution and delivery source for many public news groups, approachable over the USENET news network.
  • Proxy Server: It acts as a mediator between a client program and an external server to filter requests, improve performance and share connections.
  • Telnet Server: It enables the users to log on to a host computer and execute tasks as if they are working on a remote computer.
  • Web Server: It provides static content to a web browser by loading a file from a disk and transferring it across the network to the user's web browser. This exchange is intermediated by the browser and the server, communicating using HTTP.


نوشته شده توسط : Hiva Eskandari Pour

another types of network categorization

دوشنبه 22 فروردین 1390   03:28 ب.ظ


نوع مطلب : Network + ،

  1. Server-based Configuration
  2.  Peer-to-peer Configuration
Server-based Configuration

A server-based network consists of a group of user-oriented PCs (called Clients) that request and receive network services from specialized computers called Servers. Servers are generally higher-performance systems, optimized to provide network services to other PCs.

Some common server types include file servers, mail servers, print servers, fax servers, and application servers.

Relationship between a server and a client is same as a Teacher and a Student, where teacher provides services (of teaching) and student study. You know, student never teaches the teacher, right!

Peer-to-Peer Configuration

A peer-to-peer network is a group of user-oriented PCs that basically operate as equals. Each PC is called a peer (workstation). The peers share the resources, such as files and printers, but no specialized servers exist. Each peer is responsible for its own security, and, in a sense, each peer is both a client (because it requests services from the other peers) and server (because it offers services to the other peers). Small networks -- usually under 10 machines -- may work well in this configuration. If security is an issue, then peer-to-peer is never suitable even there are 2 computers only.

Copy R


نوشته شده توسط : Hiva Eskandari Pour

Introduction to Network Types

دوشنبه 22 فروردین 1390   01:36 ق.ظ


نوع مطلب : Network + ،

One way to categorize the different types of computer network designs is by their scope or scale. For historical reasons, the networking industry refers to nearly every type of design as some kind of area network. Common examples of area network types are:
LAN - Local Area Network
WLAN - Wireless Local Area Network
WAN - Wide Area Network
MAN - Metropolitan Area Network
SAN - Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network
CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network
PAN - Personal Area Network
DAN - Desk Area Network
LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution.
Note that these network types are a separate concept from network topologies such as bus, ring and star.

LAN - Local Area Network

A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet.

In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring.

WAN - Wide Area Network

As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth.

A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address.

A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity over the longer distances.

LAN, WAN and Home Networking

Residences typically employ one LAN and connect to the Internet WAN via an Internet Service Provider (ISP) using a broadband modem. The ISP provides a WAN IP address to the modem, and all of the computers on the home network use LAN (so-called private) IP addresses. All computers on the home LAN can communicate directly with each other but must go through a central gateway, typically a broadband router, to reach the ISP.

Other Types of Area Networks

While LAN and WAN are by far the most popular network types mentioned, you may also commonly see references to these others:
Wireless Local Area Network - a LAN based on WiFi wireless network technology
Metropolitan Area Network - a network spanning a physical area larger than a LAN but smaller than a WAN, such as a city. A MAN is typically owned an operated by a single entity such as a government body or large corporation.
Campus Area Network - a network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus.
Storage Area Network - connects servers to data storage devices through a technology like Fibre Channel.
System Area Network - links high-performance computers with high-speed connections in a cluster configuration. Also known as Cluster Area Network.


نوشته شده توسط : Hiva Eskandari Pour

How to Become a Network Engineer

یکشنبه 21 فروردین 1390   11:49 ق.ظ

Learning how to become a network engineer is in itself no easy task. The scope of topics ranges from learning where each appropriate plug goes into to mastering the use of Linux, Solaris and NetWare to optimise connections between servers and individual computers.

The rewards, however, are quite lucrative indeed, especially when you develop the latest skills and expertise in computer networking. Businesses need to stay up to date with the latest technologies, and networks are just one way for them to increase their productivity. Being a network engineer gives you employment opportunities with almost every high-tech establishment out there, which is in itself reason enough to learn the basics of network engineering.

Here are simple steps on how to become a network engineer:

Educate yourself

You must always learn to walk before you run, and network engineering is no exception. Take a computer-related university course, with a bachelor degree in Information Technology or computer and software engineering coming highly recommended. They often contain the basic knowledge about computer networking, while the diploma serves as testament to your skills with computers. The structured learning process also helps to ensure your ability to network computers, especially if you are comfortable in an academic setting.

It is important to note, however, that university is not the only way to familiarise yourself with computers. The basic exposure necessary for you to learn the ups and downs of network engineering can be learned through self-study, but you have to exert a lot of time and effort to look around for resources to get your knowledge from in the first place. You can then gain network engineering credibility by obtaining certification from institutions like Cisco, Novell, or Microsoft. This will prove to prospective employers that you know your stuff, assuring them that you are up to the challenge.

Cultivate your problem solving and communication skills

Learning how to become a network engineer is not just about computers, connections, and operating systems. You are going to be bombarded with problems left and right and you are going to have to explain this to your not-so-tech-savvy bosses and customers.

Working under pressure, identifying potential problems and coming up with quick solutions are some of the more hands-on requirements of being a network engineer. Social skills, however, are essential to gain and maintain the cooperation of others around you. This means you need to resolve conflicts, deal with difficult people, and be a 'leader' of sorts in order to cultivate your communication skills.

Acquire as much on-the-job training as possible

If there is one last thing you need to remember about being a network engineer, it is to acquire as much practical experience as possible.

Internship in either your school's IT department or local companies looking for young blood is the best ways to learn how to become a network engineer. You will be able to hone your skills in a working environment, getting a grip on everything that a network engineer has to do. The pay may be less or non-existent at all, but the experience you'll gain from being an intern is something that will teach you all you need to learn about how to become a network engineer. 


نوشته شده توسط : Hiva Eskandari Pour