What is a network? You have probably heard of a computer network. Maybe you even have one (perhaps you've heard people say, "No e-mail today -- the network's down" or "No Internet today - the router isn't working"). Maybe you need one (you often hear people say, "Can you turn the printer switch to letter 'D'" or, "Can you pass me that disk"). Whatever your needs, you may be wondering, "What exactly is a network?" In the simplest terms, a network consists of two or more computers that are connected together to share information. All networking, no matter how complex, builds off this simple system. Though this may seem like a basic idea, the concept was a major achievement in communications. What makes up a network? A network typically includes four things (besides the computers themselves): Protocol: a set of communication rules to make sure that everyone speaks the same language Network interface cards (NICs): cards that plugs into the back (or side) of your computers and lets them send and receive messages from other computers Cable: the medium to connect all of the computers together Hub: hardware to perform traffic control Note: The key word is "typically." Wireless networks obviously don't use cables and NICs aren't necessary for small networks that use parallel/serial ports. But the basics still apply. How does a network work? How does one computer send information to another? It is rather simple. The diagram below shows a simple network: If Computer A wants to send a file to Computer B, the following would take place: Based on a protocol that both computers use, the NIC in Computer A translates the file (which consists of binary data -- 1's and 0's) into pulses of electricity. The pulses of electricity pass through the cable with a minimum (hopefully) of resistance. The hub takes in the electric pulses and shoots them out to all of the other cables. Computer B's NIC interprets the pulses and decides if the message is for it or not. In this case, it is, so Computer B's NIC translates the pulses back into the 1's and 0's that make up the file. Sounds easy. However, if anything untoward happens along the way, you have a problem, not a network. So, if Computer A sends the message to the network using NetBEUI, a Microsoft protocol, but Computer B only understands the TCP/IP protocol, it will not understand the message, no matter how many times Computer A sends it. Computer B also won't get the message if the cable is getting interference from the fluorescent lights, or if the network card has decided not to turn on today. Network classification Like snowflakes, no two networks are alike. So for the sake of discussion, it helps to classify them by some general characteristics. A given network can be characterized by its: Size: the geographic size of the network Security and access: who can access the network and how access is controlled Protocol: the rules of communication in use on it (for example, TCP/IP, NetBEUI, or AppleTalk) Hardware: the types of physical links and hardware that connect the network Size (LANs and WANs): Regarding size, networks are generally lumped into two categories, local area networks (LANs) and wide area networks (WANs). A LAN is primarily defined by geography, and is typically housed in one building or campus. A WAN, on the other hand, is a network that joins many LANs together using super special, highly secret, WAN technologies, but we will delve into that arena some other day. Hopefully you're still reading. Because they are so common, LANs are usually further divided into two major types: Peer-to-peer: A peer-to-peer network doesn't have any dedicated servers or hierarchy among the computers. All of the computers on the network handle security and administration for themselves. The users must make the decisions about who gets access to what. Client-server: A client-server network works the same way as a peer-to-peer network except that there is at least one computer that is dedicated as a server. The server stores files for sharing, controls access to the printer, and generally acts as the dictator of the network. Protocol As stated above, the protocol of a network is the set of guidelines for inter-computer communication. Two computers with different protocols won't be able to communicate with one another (imagine Ralph Nader and Pat Buchanan in the same room). While many computers have the ability to interpret multiple protocols, it is important to understand the different protocols available before deciding on one that is appropriate for your network. Hardware While some theoretical people would claim that the hardware involved in a network isn't extremely important, they probably haven't ever actually dealt with setting one up. Hardware is important. While in theory, every hub should send and receive signals perfectly, that isn't always the case. And the problem is that if you ask two network administrators what hub they recommend, you will probably get two entirely different, yet passionate answers. From picking the cable (optical fiber, coaxial, or copper), to choosing a server, you should find the most suitable hardware for your needs. Peer to Peer Networks Networks can allow computers, servers, and other devices to talk to each other. There are a number of different types of networks, and it's important to find the right one to fit your library's needs so that you don't waste time and money with one that is too complex, or one that doesn't suffice. If you only need to share a printer or an Internet connection, a client-server network might be overkill. Sometimes, a simpler peer-to-peer network may be all you need. The diagram below shows a simple peer-to-peer network: As you can see from the diagram, in a peer-to-peer network there are no dedicated servers or any kind of hierarchy among the computers. All of the computers on the network handle security and administration for themselves. The users must make the decisions about who gets access to what. Beyond that, there are more similarities between the types of networks than differences. All the computers must have network cards. You also use the same cables, the same hubs and switches, and the same protocols as you would with a client-server model. The only difference is that with a peer-to-peer setup there is no server. Since there isn't a server, there are some things you need to think about before you go down the peer-to-peer path. Before taking the plunge Peer-to-peer networks work remarkably well in certain circumstances; however there are a few things to consider before setting one up: Size Peer-to-peer networks are designed to connect a small number of computers. They tend to run into problems at around 10 to 15 computers. Security Security on a peer-to-peer network is not very powerful. So if you have security concerns, go for something you can control (like a server). Because the users will be required to give access to folders, they can choose not to require passwords. This lack of hierarchy has a tremendous impact on the security of your network and you will need adequate training for your users to prevent problems. Growth If your library's computer system is growing rapidly, it will likely outgrow a peer-to-peer network very quickly. While a peer-to-peer network may work fine for 10 computers, it probably won't for 20. Training In a peer-to-peer network, the users handle administration. This means that all the users need to be trained in how to share files, folders, and printers. In a peer-to-peer network, suddenly shutting down your computer can cause one of your colleagues to be unable to print. Hosting resources Each computer that attaches to another computer, whether for printing or for file sharing, takes up system resources on the host computer. If the drain becomes dramatic enough to slow down the host computer, then perhaps it is time to start thinking about a dedicated server. What are your options? If you've assessed your situation, and you've determined that a peer-to-peer network is appropriate for your library, the setup can be relatively simple if you are using one of the common operating systems available today. Macintosh The Macintosh operating system has included peer-to-peer network capability for many years. You even have the option to set up the network with phone lines and very simple connectors. For more detailed information see, How to Create a Small Ethernet Network, a guide from Apple on setting up a small peer-to-peer network. Windows 95/98/ME/2000/XP Windows 95, 98, ME, 2000, and XP all include the capacity for peer-to-peer networking and can be set up with limited hardware expenditures. For detailed information, see the following: Cross-Platform It is possible to connect your Macs and your PCs together on one network. The resources below tell you how to do this: Connectivity between PC-Compatible and Macintosh Computers on a Network Information from Apple on connecting PCs to a Mac network. The ultimate source for Macintosh-Windows compatibility and networking information. Conclusion A peer-to-peer network is sometimes the perfect (and cheap) solution for connecting the computers at a small library. However, peer-to-peer networking has its limitations, and your library should tread with caution to avoid headaches (security issues, hardware inadequacies, and backup problems) down the road. Client Server Networks While a peer-to-peer network is often a good choice for small networks, in an environment with more than 10 to 15 computers, a peer-to-peer network can become more trouble than it is worth: Your computers start to slow down, you can never find the file you are looking for, and security is non-existent. If this is happening in your library, it is probably time to switch to a client-server network by bringing in a dedicated server to handle the load. The server is called "dedicated" because it is optimized to serve requests from the "client" computers quickly. The diagram below shows a simple client-server network: What is a server? A server is simply a computer that is running software enabling it to serve specific requests from other computers, called "clients." For example, you can set up a file server that becomes a central storage place for your network, a print server that takes in print jobs and ships them off to a printer, and a multitude of other servers and server functions. A server provides many benefits including: Optimization: Server hardware is designed to serve requests from clients quickly. Centralization: Files are in one location for easy administration. Security: Multiple levels of permissions can prevent users from damaging the files. Redundancy and backup: Data can be stored in redundant ways, making it easy to restore in case of problems. A server, like any computer, consists of two parts -- the hardware and the software. Server hardware basics Any desktop computer can act as a server, but typically you want something much more robust. Standard server hardware includes: Hot-swappable drives (drives that can be replaced while the computer is running) to speed up adding or replacing hard disks. The ability to support multiple processors. Support for larger amounts of RAM. Faster input and output. Fast network cards. Redundant components, such as hard drives and power supplies, to cut down the chance of computer failure. Server software basics Server software comes in two categories -- operating systems and applications. Network operating systems There are many different operating systems for servers just like there are many different operating systems for desktop computers. Windows Server (NT, 2000, and 2003), Linux, and Novell Netware are the three main network operating system competitors, but they are most assuredly not the only ones (there will always be the occasional OS/2 WARP fanatic screaming from a soapbox). A Network Operating System (NOS) will have many features built in. All will include file serving, print serving, backup, and some way to secure those resources. Some NOSs will include a Web server or mail server, while others require you to buy these items separately. Research all the options before making a decision on the NOS for your server. Figure out precisely what you want by browsing through Web sites and sales pamphlets. Then try to find a computer guru who knows your library's network and ask this person about what would work best. If you can, try to make sure that this is not the same person who would be doing the work or selling you the product, otherwise there may be a conflict of interest. This is a big decision, and it will dramatically affect all of your future computer transactions and operations. Server applications Server applications can be designed for nearly every purpose imaginable, from fax servers to remote access servers. Every application will have specific server requirements, and typically will be designed to run on Windows NT/2000, Linux, or Netware. Many servers run multiple applications (like e-mail and faxing) to serve a variety of needs. Last thoughts The client-server model of networking is the way to go for larger networks or libraries. Once you have a client-server network set up, it should provide you with more flexibility than a peer-to-peer network as your needs change. For example, as network traffic increases, you can add another server to handle the additional load. You can also consider spreading out tasks among various servers, ensuring that tasks are performed in the most efficient manner possible. Most importantly, a client-server network is much easier to secure and back up, and greatly improves the reliability and confidentiality of your data. Server Applications Computer networks can range from a simple peer-to-peer network to a more complex client-server network. While a complicated network can generally perform more advanced functions, it requires more involved planning, particularly regarding the server application. If you have a client-server network, you are probably using the server to share files and printers, and you may also be using it to host a Web site or e-mail. If you are, then you probably are using server applications. If you aren't, then you need them. Servers are designed for nearly every purpose imaginable, from simple e-mail servers to more complicated application servers. Every application will have specific server requirements, and is typically designed to run on Windows NT/2000, Novell Netware, or Linux. Many servers can run multiple applications to serve a variety of needs. As your network grows, you will find uses for a variety of specialized server applications. The following is just a brief introduction to the most common types of server applications. File and print servers File and print servers are typically combined on one server and perform as part of the network operating system. The file and printer servers manage the storage of data and the various printers on the network. These servers regulate and monitor access to these resources. The three most popular are: Mail servers Mail servers manage local (within your network) and global (Internet-wide) electronic messaging. The mail server you choose should support the Internet standards such as POP3 and SMTP. Sometimes they even incorporate entire groupware solutions: managing calendars, contacts, group meeting scheduling, and other operations. There are many examples of mail servers, but the most popular are: List servers While many mail servers offer the capability to serve an e-mail listserv or mass e-mail distribution, there are some servers that handle those tasks exclusively. Here are a few to look at: Fax servers Fax servers manage fax traffic in and out of the network, allowing multiple users to send and receive faxes without a fax machine. Most of the popular e-mail servers have fax servers that you can buy and integrate into your system, so look there first. One interesting note is that Microsoft Small Business Server (basically their BackOffice software for fewer than 30 users) includes a fax server. However, they didn't include it in Windows 2000. Some other examples of standalone fax servers are: Web servers Web servers allow Internet users to attach to your server to view and maintain Web pages. Web browsers such as Netscape and Internet Explorer request documents from the Web server using standard protocols, and the Web server retrieves the requested documents and forwards them on to the browsers. Web servers support a variety of technologies including CGI scripts, Active Server Pages, and secure connections to extend the power beyond the basic HTML code. The two most popular Web servers are: Apache (for “A patchy” Web server) One interesting thing is that this field is primarily the domain of Linux and Unix (with Apache). However, Microsoft has been playing catch-up, and it is gathering support around its IIS product. Database servers or database management systems (DBMS) Though not exactly a server, DBMS systems allow multiple users to access the same database at the same time. While this functionality is typically built into database software (ex. Microsoft Access allows concurrent connections to its databases), a larger database, or a database with many users, may need a dedicated DBMS to serve all the requests. Examples of these include: Application servers Application servers have undergone many changes and have grown in both quantity and variety with the growth of the Internet. Basically, an application server acts as an intermediary to information. Here is a typical situation: 1. A client makes a request for information (often as a database request). 2. The application server passes that request on to the application. 3. The application processes the request and sends the results to the application server, which then returns the results to the client. 4. The client gets the results of their query without needing to download the whole database to his or her workstation. In many usages, the application server works with a Web server and is called a Web application server. The Web application server receives requests from a Web page then returns the information in a new Web page based on the results and uniquely created. The technology to do this typically involves the Common Gateway Interface (CGI) Microsoft's Active Server Pages (ASP) , or Java Server Pages (JSP). Examples of application servers include Cold Fusion. Once again, this is just the tip of the iceberg. There are many more application servers available. For a more detailed introduction to all of these servers see: DevX.com. Terminal servers or communication server Generally, a terminal server refers to a piece of hardware that allows devices to be attached to the network without a need for network cards. PCs, “dumb” terminals supporting just a mouse and monitor, or printers can all be attached via standard ports, and can then be managed by the network administrator. However, Microsoft has co-opted this term and changed it to fit their purposes. A Microsoft Terminal Server is a program running on its Windows NT 4.0 operating system that provides the graphical user interface of the Windows desktop to user terminals that don't have this capability themselves. The latter include the relatively low-cost Net PCs or “thin clients” that some companies are purchasing as alternatives to the autonomous and more expensive PC with its own operating system and applications. In the past, Terminal Server required an entirely different operating system version, but Microsoft has expanded this capability to be a standard application in Windows 2000. Proxy servers Proxy servers act as intermediaries between your network users and the wide world of the Internet. Proxy servers perform a number of functions: Masks your network users IP addresses Strengthens security by only allowing certain requests to come through and by providing virus protection Caches Web page data for a given period of time to allow for more rapid access Examples of proxy servers include: Conclusion The preceding list is only an introduction to common server applications. With the amount of time and money thrown at the Internet, many types of servers are springing up to fill every conceivable need. Whether you need to start up an e-mail list, or provide access to talk radio 24 hours a day, there is a server for you. For a detailed examination of the various types and competitors in each of these markets, we recommend visiting the holy grail of server information: ServerWatch.
Documents
| Introduction to Networking |
This all-in-one article compiles a series of networking articles including basic networking, peer-to-peer, and client-server networks in order to give you a full overview of networking generally.
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