Network construction

• LAN (Local Area Network) means the computer network which connected two or more PCs. Recently, as for a company, it is not new that even the individual, of course, owns two or more PCs, either. It is the thing of the technology which connects and carries out the resources share of two or more PCs by the network. The example which is building "domestic LAN" does not have few individual users who own two or more sets of PCs in domestic, either. Many merits which are not in stand-alone use can be pulled out by building LAN.

• Internet connectivity environment . -- it is, changing abruptly Ages Although the dialup connection by . telephone circuit was in use at home, they are . now and a Broadband. Super-high speed and service of a low charge are offered by maintenance of an infrastructure also at . each home. The merit by share of the Internet environment by LAN construction has in it the thing which is not. Measured and found.
  
  
• The merit of No. 1 of LAN construction is that a share of data or a file and speedy transmission are attained. Although it was common to have used a floppy disk to delivery of a file when it was the former, recently, a document is not settled in one floppy disk more often, either. Moreover, using the same data, former data is copied with different PC, and there is only passing by the floppy disk etc. too. The inefficient thing understands at least time. Moreover, not only it but data is usually updated always. if new data is added by mistake, it will become a due to occupational cases mistake before inefficient if a copy is not allowed in order to prevent a mistake, one set only of PC with which it was memorized can use data, but there is no merit of the computerization of "being in a required place about required data when required" -- it will be alike and will become equal It becomes indispensable in order for "an informational share" by network to pull out the merit of computerization of a system to the maximum extent.
  
  
• It is considered [ to which PC a printer is connected, wavering in many cases, and ] when stand-alone use of two or more sets of the PCs is being carried out in the small-scale company. Even if it removes the special business to which a printer operates at full swing and it usually has 4-5 PCs, one set is of use for a printer. I consider [ using properly the dot impact printer and the usual LASER beam printer color printer which print a copy list in many cases again, and ]. If this is used by the stand-alone, even PC to which the target printer was connected has only carried [ the method ] data by the floppy disk. In a design-related office, in case a lot of data is exchanged, since time is taken too much, by communication, you have to exchange data using mass external memory media, such as MO and Zip. It is very inefficient-like to purchase those drives by the number. If a network is introduced, the peripheral equipment connected to a certain PC can be freely used to other PCs. If it is a small-scale network, if there are MO and one Zip drive, they are enough, and a printer is also the number of necessary minimum and they end.
  Till a decade ago [ peer to peer ], although the change of a personal computer was transposing old PC to new PC literally, with the latest PC with which a mass hard disk is becoming natural, serious work is needed for moving a lot of data of PC to throw away to new PC. If network connection will be first made if it is PC of a level with which Windows 95 works except a machine [ like / before Pentium ] whose CPU is, data is transmitted and a printer is connected after that, work of print-out will be left to the old PC, and a machine will work more efficiently by reducing the burden of new PC.

Peer to peer connection


• LAN constituted, using the network function which Windows 95 and Windows 98 have as it is. With this composition, each PC is treated on equal terms. When there are only sets [ several ] PCs to use in SOHO or a very small-scale company, it can be said that this is enough. If they are wide opened on LAN, using as a shared resource the hard disk and printer which are connected to a certain PC, use of it will be attained from every PC. Since introduction and an addition are easy, while LAN begun by 2-3 sets at first calls it as for this type of LAN, it is not new to become ten or more sets, either. However, in such spontaneous LAN, various problems occur as the number of PC increases. It is because there is a weak point "a possibility that an obstacle will be encountered as the number increases is high." For example, it is also considered that PC user of a transmission place drops a power supply during transmission of a file, and it uses disorderly and the problem that the files of the same name will be scattered on LAN also tends to arise. In order to prevent such an obstacle, the method of centralizing shared resources, such as a file and a printer, on specific PC is effective. This is the fundamental view of client server type LAN.
  
  Client server connection
  
• With a client/server system, the computer called server which processes a demand of a client apart from each PC (client) is used. The server is made to usually work by uninhabited for 24 hours. In small-scale LAN, although the number of the servers which manage a network is one, if a scale becomes large, the server machine according to uses, such as a server which manages a database, is needed. Moreover, although the network was built using the basic network function of Windows 95/98, with a client server type, software called Network OS is needed peer to peer one. In NOS, the present WindowsNT and UNIX system are [ two ] in use. In the case where stability, such as an internal network, is thought as important, it becomes indispensable. It is because influence will attain to the whole LAN if an obstacle occurs in a server unlike a client. Moreover, the security protection in LAN can also check a user with user ID and a password by one of the important reasons NOS is needed, and can perform resources protection and access restrictions according to it. For example, the demand of "wanting to restrict the information which can be accessed for every user" is started frequently in an internal network. It is possible if the usage of opening a file only to the member in relation to the project, or distinguishing the range of the data which can be accessed in a general employee and a general managerial position is also NOS.

• The same LAN, such as a room where the composition of LAN lays the number of PC or a printer and LAN, a building, and a way, a user's level to use, does not exist with two at all. Then, I introduce the foundation of network construction
  
  First, wiring of LAN is important when building a network. It is common to wire a star type in PC centering on a hub as a fundamental wiring style using a twisted-pair cable.
  
  however since it to a hub in the case where PC is gathering in the place from which it is separated when there is much number of PC, although one hub is enough while it is small-scale a hub the necessity of connecting comrades comes out
  
  The network consists of many LAN on the basis of the standard of Ethernet. In Ethernet, data is divided and transmitted to the small unit called packet. The quantity and time of the data sent at once by dividing data are shortened, and it enables it to use a network simultaneously with two or more PCs. However, if it says strictly, there is restriction that only one packet can be sent simultaneously, in the unit (segment) of one LAN.
  
  Generally the first Ethernet (100BASE-TX) in which the communication speed in Ethernet (10BASE-T) has one (100Mbps) 10 times the communication speed of this 10Mbpses and recently also came to be used. If LAN is newly built after this, it is the first Ethernet from the start.
  
  It will be better to come out and make a plan. However, various problems also arise by communication speed having increased 10 times. a hub -- the connection conditions of comrades become severe and the case where the apparatus which is supporting only 10BASE-T like the existing router or a print server must be made intermingled in a network also happens
  
  Then, in order to build LAN well, it is becoming important to get to know the kind and the feature of a hub.
  
  a hub large dividing "dam a hub "" dual speed a hub " there are three kinds of " and a "switching hub"
  
  most fundamental "dam a hub although price is also cheap and introduction is also easy, if " remains as it is, it cannot make 10BASE-T and 100BASE-TX intermingled
  
  the point " dual speed a hub if " is used, mixture environment can be built easily Although a "switching hub" is an expensive hub, there is a reason in it perfectly. This is a hub for making the performance of the whole LAN raise.
  
  In Ethernet, dividing data for every packet may transmit a packet simultaneously from two or more PCs in fact, although explained above. If this is called collision (collision) of a packet and collision occurs, data cannot be sent correctly. When the number linked to LAN increases, generating of this collision of thinking, "Something became late" is the cause.
  
  In a "switching hub", the port which the load to which the server etc. is connected in being able to suppress generating of collision by learning transmission and reception of a packet automatically and sending a packet only to a specific port tends to concentrate can be used efficiently.
  
  a hub there are two kinds of the methods of connecting comrades, "cascade connection" and "stack connection"
  
  "cascade connection" a hub comrades are connected by the twisted-pair cable It will be better not to use, if it can do, although the product with the connector of 10BASE-2 using a coaxial cable is also in a hub. It is because there are no 100BASE-2 even if there are 10BASE-2. If it will change to first Ethernet in the future, even when it is easy to exchange a hub, it is serious to redo wiring work.
  
  Moreover, "cascade connection" of the hub cannot be made without any restriction. It is because there is a rule called two or less steps by four or less step 100BASE-T at 10BASE-T in order to detect collision.
  
  In "stack connection", two or more hubs are accumulated (stack) and the whole is recognized as one set of a hub. Although it is convenient when there is much number of PCs to connect, such as relief of collision conditions, it is necessary to use the product corresponding to "stack connection."