However, the size and speed of the server's processor s , hard drive, and main memory might add dramatically to the cost of the system. On the other hand, a workstation might not need as much storage or working memory, but might require an expensive display to accommodate the needs of its user. Every computer on a network should be appropriately configured for its use. On a single LAN, computers and servers may be connected by cables or wirelessly.
Wireless access to a wired network is made possible by wireless access points WAPs. These WAP devices provide a bridge between computers and networks. A typical WAP might have the theoretical capacity to connect hundreds or even thousands of wireless users to a network, although practical capacity might be far less.
Nearly always servers will be connected by cables to the network, because the cable connections remain the fastest. Workstations which are stationary desktops are also usually connected by a cable to the network, although the cost of wireless adapters has dropped to the point that, when installing workstations in an existing facility with inadequate wiring, it can be easier and less expensive to use wireless for a desktop.
See the Topology , Cabling , and Hardware sections of this tutorial for more information on the configuration of a LAN. Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of global network. Using a WAN, schools in Florida can communicate with places like Tokyo in a matter of seconds, without paying enormous phone bills. Two users a half-world apart with workstations equipped with microphones and a webcams might teleconference in real time.
A WAN is complicated. It uses multiplexers, bridges, and routers to connect local and metropolitan networks to global communications networks like the Internet. Florida Center for Instructional Technology. College of Education ,. University of South Florida ,. This publication was produced under a grant from the Florida Department of Education. The information contained in this document is based on information available at the time of publication and is subject to change.
Although every reasonable effort has been made to include accurate information, the Florida Center for Instructional Technology makes no warranty of claims as to the accuracy, completeness, or fitness for any particular purpose of the information provided herein. Nothing herein shall be construed as a recommendation to use any product or service in violation of existing patents or rights of third parties.
What is a Network? Advantages of Installing a School Network User access control. To conserve system resources, disable the ports for protocols that you do not need. Topics in this section describe how to set up users and servers. INI file. An accidental or incorrect change may cause Domino or Notes to run unpredictably.
INI file only if special circumstances occur or if Support recommends that you do so. This section provides an overview of messaging and describes how to set up mail routing, how to set up and customize mail servers, and how to track mail. Administrators specify mail policy and security policy settings as well as notes.
Setting up a cluster includes the tasks of creating and verifying that it is working correctly, and then setting up user access, mail, replications, size quotas, directory assistance, roaming, web navigation, and use of a private LAN in the cluster.
Let's look at another diagram: Diagram 3 Here we see Diagram 1 redrawn with more detail. The physical connection through the phone network to the Internet Service Provider might have been easy to guess, but beyond that might bear some explanation.
The ISP maintains a pool of modems for their dial-in customers. This is managed by some form of computer usually a dedicated one which controls data flow from the modem pool to a backbone or dedicated line router. This setup may be refered to as a port server, as it 'serves' access to the network. Billing and usage information is usually collected here as well.
From here the packets will usually journey through several routers and over several backbones, dedicated lines, and other networks until they find their destination, the computer with address 5. But wouldn't it would be nice if we knew the exact route our packets were taking over the Internet? As it turns out, there is a way This one is called traceroute and it shows the path your packets are taking to a given Internet destination. Like ping, you must use traceroute from a command prompt.
In Windows, use tracert www. From a Unix prompt, type traceroute www. Like ping, you may also enter IP addresses instead of domain names. Traceroute will print out a list of all the routers, computers, and any other Internet entities that your packets must travel through to get to their destination. If you use traceroute, you'll notice that your packets must travel through many things to get to their destination. Most have long names such as sjc2-core1-h These are Internet routers that decide where to send your packets.
Several routers are shown in Diagram 3, but only a few. Diagram 3 is meant to show a simple network structure. The Internet is much more complex.
Internet Infrastructure The Internet backbone is made up of many large networks which interconnect with each other. These networks peer with each other to exchange packet traffic. NAPs were the original Internet interconnect points.
Below is a picture showing this hierarchical infrastructure. Diagram 4 This is not a true representation of an actual piece of the Internet. None of the physical network components are shown in Diagram 4 as they are in Diagram 3. This is because a single NSP's backbone infrastructure is a complex drawing by itself. Most NSPs publish maps of their network infrastructure on their web sites and can be found easily. To draw an actual map of the Internet would be nearly impossible due to it's size, complexity, and ever changing structure.
Does every computer connected to the Internet know where the other computers are? Do packets simply get 'broadcast' to every computer on the Internet? The answer to both the preceeding questions is 'no'. No computer knows where any of the other computers are, and packets do not get sent to every computer. The information used to get packets to their destinations are contained in routing tables kept by each router connected to the Internet.
Routers are packet switches. A router is usually connected between networks to route packets between them. Each router knows about it's sub-networks and which IP addresses they use. The router usually doesn't know what IP addresses are 'above' it. Examine Diagram 5 below. The black boxes connecting the backbones are routers. Under them are several sub-networks, and under them, more sub-networks. At the bottom are two local area networks with computers attached.
Diagram 5 When a packet arrives at a router, the router examines the IP address put there by the IP protocol layer on the originating computer. The router checks it's routing table. If the network containing the IP address is found, the packet is sent to that network. If the network containing the IP address is not found, then the router sends the packet on a default route, usually up the backbone hierarchy to the next router.
Hopefully the next router will know where to send the packet. If it does not, again the packet is routed upwards until it reaches a NSP backbone. The routers connected to the NSP backbones hold the largest routing tables and here the packet will be routed to the correct backbone, where it will begin its journey 'downward' through smaller and smaller networks until it finds it's destination.
What if the you need to access a web server referred to as www. How does your web browser know where on the Internet this computer lives? The DNS is a distributed database which keeps track of computer's names and their corresponding IP addresses on the Internet.
Many computers connected to the Internet host part of the DNS database and the software that allows others to access it.
0コメント