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Section 2: <br>Understanding Networking<br><br>Networking can be a complex subject and unfortunately the 150 hours that we have available to us will only let us scratch the surface. However, don’t panic… becoming a successful network professional does not necessarily require 7 years of full-time study towards a Ph.D. in computer science. There are a lot of features to networking, and this tends to make the subject appear more complex than it really is. In this section you will learn about the fundamental aspects of networking, laying the foundations for more detailed features to follow…<br><br>N.B.I’ve placed a networking glossary in my library area. Most people leave glossaries until they come upon a word they are not sure about. I would instead recommend that you spend a few minutes becoming familiar with the definitions, so that you don’t miss any terms that are used.<br><br>1.0Network Features<br>Understanding the types of things you can do with a network is the first logical and important step to understanding networks as a whole. Therefore the following paragraphs discuss common network features and capabilities.<br><br>1.1File Sharing<br>Originally file sharing was the primary reason behind implementing a network. In fact small and medium sized companies in the mid-1980s usually installed networks just so that they could perform this function. Often this was driven by the need to computerise and share the accounting system files, however once the networks were in place sharing other types of file (e.g. word-processing, spreadsheets…) became commonplace. <br><br>File sharing requires a shared folder or disk drive (usually housed on a file server) to which many users can access over the network, along with the ability to make sure more than one person doesn’t make conflicting changes to that particular file at the same time (called file locking). Additionally, NOSs that perform file sharing (basically all of them these days) also administer the security for those shared files. This security can control, to a fine level of detail, who has access to which files and what kinds of access they have. For example one particular user may have permission to only view (or read) a certain shared file, whilst another user may be able to edit (modify) or even delete (full control) that same file.<br><br>1.2Printer Sharing<br>A close runner-up in the importance stakes to file sharing is printer sharing. While it is true that black and white laser printers are now so relatively cheap that each workstation can afford to have its own printer, sharing laser printers among the users on the network is still more economically viable overall. While printer sharing enables you to reduce the total number of printers needed (as well as installation and administration overheads), it also enables you to offer much higher-quality printers. <br><br>The most common way to share the printer over a network is to use printer queues. A printer queue holds print jobs until any currently running print job is finished and then automatically sends the next waiting job in the queue to the printer. Using a printer queue is efficient for workstations because they can quickly print to the printer queue without having to wait for the printer to process their job. Networked printers that use a printer queue always have a print server that handles the job of sending each print job to the printer in turn. The print server function can be filled in a number of ways:<br>&#8226&#59;By a fileserver with the printer directly connected to it (this is not recommended as it can have adverse effects on the fileserver’s performance)<br>&#8226&#59;By a computer connected to the network, with the printer connected to that computer. The computer runs special print server software to perform this job a popular traditional means).<br>&#8226&#59;Through the use of a built in print server on a printer’s NIC. For example all modern HP printers offer an option to install a NIC in the printer. This card also contains the ‘computer’ necessary to act as a print server.<br>&#8226&#59;Through the use of a dedicated network print server box (also known as a network printer appliance). This small hub-like box connects to the printer’s parallel or USB port (or even a wireless 802.11a or 802.11b connection) on one end and to the network on the other end. Dedicated print servers also contain the ‘computer’ necessary to act as the print server.<br><br>1.3Application Services<br>Just as you can share files over a network, you can also share certain applications on a network. For example, you can have a shared copy of Microsoft Office located on an application server, from where it is also run. When a workstation wants to run the program, it loads the files from the network into its own memory, just like it would from a local disk drive, and runs the program normally. Keeping the application centralised reduces the amount of disk space required on each workstation, and makes it easier to administer the application (e.g. upgrading versions, adding critical patches).<br><br>Another application service that can be run over a network is a shared installation point for applications. This involves copying the contents of an application from CD/DVD onto the server, and then have the installation program run from the server for each workstation. This makes installing the applications much faster and more convenient.<br><br>1.4Internet and Intranet<br>There’s no way around the fact that the Internet has become a vital productive entity for most businesses, and handling Internet connectivity is often an important part of the network. Many different types of services are available over the Internet, including email (see below), forums, and electronic resources.<br><br>An Intranet as its name suggests, is an internally focussed network that mimics the Internet itself. For example NMIT has its own Intranet service, where you can find tutor resources, administration documents and other information. Intranets are not usually accessed from outside the corporate network (although they can be) and are just a much smaller version of the Internet that a company maintains for its own use. <br><br>1.5Email<br>An extremely valuable and important network resource these days is email. Not only is it an essential form of communication within a company, but it has become the preferred vehicle of communication outside a company as well. <br><br>Unless a company has at least 50 employees, dedicated email servers are usually an overkill and are costly to purchase and maintain. For smaller companies there are strategies to provide email services to the employees. For instance many small companies simply set up a shared connection to the Internet that all of their computers can access and then set up email accounts either through their ISP or through a free email service such as Yahoo or Hotmail.<br><br>1.6Remote Access<br>Another important service for most networks is remote access to the network resources. Users use this facility to access their files or email when they’re travelling or working from a remote location, such as their home. Remote access systems come in many different forms:<br>&#8226&#59;Setting up a simple Remote Access Service (RAS) connection on a Windows 2003 Server, which can range from using a single modem to a bank of modems<br>&#8226&#59;Employing a workstation on the network and having users dial in using a remote control program like PC Anywhere.<br>&#8226&#59;Setting up a Virtual Private Network (VPN) connection to the Internet, through which users access resources on the company network in a secure fashion through the Internet.<br>&#8226&#59;Installing Windows Terminal Services (on Windows 2003) or Citrix MetaFrame, both of which allow a single server to host multiple client sessions, each one appearing to the end user as a stand-alone computer.<br><br>The above sample of techniques indicate that there are many ways to offer remote access services to users of the network. The right solution depends on what the users need to do remotely, how many users exist (both in total and at any given time) and how many dollars the company wants to spend. <br> |
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发表于 2005-3-1 13:29:45
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