network computer

network computer OSI AND TCP/IP,NETWORK APLICATION

Definitian of  OSI and TCP/IP

OSI is a conceptual model consisting of seven layers, each layer has a different function. OSI was developed by the international agency that is ISO (International Organization for Standardization) in 1977.

This OSI Layer model

OSI Layer Model

There is a layer of the OSI 7 layer that has its own task. In general this layer 7 is classified into two main layers of the Upper Layer and Lower Layer. Lower Layer is where the process of data communication over a network, such as the sharing of data segments, the change data into bits, etc.. Upper layers can be said as a visualization of the work happens in the lower layer, examples of jobs done upper layer is a representation of the file on the screen.

The functin of each layer in OSI :

1.Layer Physicsal

Physical Layer is the layer of the simplest, relating to electrical (and optical) connections between devices. This layer Serves to define the network transmission media, signaling method, synchronization bits, network architecture (such as Ethernet or Token Ring), network topology and pengabelan. In addition, this level also defines how the Network Interface Card (NIC) can interact with the media cable or radio.

2.Layer  file-link

Data link layer is responsible at the end of the package binary data derived from a higher level into discrete packets before the physical layer. Will send frames (block of data) via a network. Protocol on the data-link layer is Ethernet (802.2 & 802.3), Tokenbus (802.4) and Tokenring (802.5).

In general, the functions of the Data Link Layer

are:

1. Framing: Divide the bit stream that

received from the network layer into

2. Physical addressing: the definition of identity

sender and / or receivers

added in the header.

4. Flow Control: take action

to create a stable bit rate if the rate

or excessive bit rate stream or

reduced.

5. Error Control: the addition of

detection and retransmission mechanisms

frames that failed messages.

6. Communication Control: determines

device that must be controlled at

certain time if there are two connections

same

                                  

3. Network layer

 Network layer provides routing functionality so that packets can be sent out from the local network segment to a destination that is on a network other.

Some network layer functions:

 - Divide the binary data stream into discrete packets with a certain length

 - Detect Error

 - Fix error with resend the corrupted packet

 - Controlling the flow

4.Layer Transport

Transport layer is the center of the fashion-OSI. Serves to break down data into packets of data and provide the serial number of the packages that can be rearranged on the side of the goal as it arrives.

5.Layer session

This layer coordinates communication between the layer entities they represent. Serves to define how the connection can be established, maintained, or destroyed. In addition, at this level also performed name resolution. Some of the protocol at this layer: NETBIOS: a session interfaces and protocols, developed by IBM, which provides service to the presentation layer and application layer. NETBEUI, (NETBIOS Extended User Interface), a development of NETBIOS used in micro ** oft networking products, such as Windows NT and LAN Manager. ADSP (AppleTalk Data Stream Protocol). PAP (Printer Access Protocol), which is found on a Postscript printer to access the AppleTalk network.

6.Layer Presentation

Serves to translate the data to be transmitted by the application into a format that can be transmitted over the network. The protocols are in this level is redirektor software (redirector software), such as Workstation service (in Windows NT) and Network shell (a sort of virtual network computing (VNC) or Remote Desktop Protocol (RDP).

7.Layer Aplication

Application Layer is the primary interface between applications running on one computer and network resources that require access to it. Application layer is the layer where the user will operate it, protocols such as FTP, telnet, SMTP, HTTP, POP3 is the Application layer.

In general, the function of application layer

 are as follows:

 •  Support for file transfer

 •  The ability to perform

 printing (print) on the network

 •  Electronic mail (email)

 •  Sending electronic messages (electronic

 messaging)

 •  Perform browsing on the World Wide

 web

The workings of the OSI

What do the seven layer OSI?

When data is transferred over the network, before the data must pass through all seven layers of a single terminal, ranging from physical layer to application layer, then on the receiving side, the data is passed through physical layer applications. At the time of data through one layer of the sending side, it will add a "header" while on the receiving end "header" removed in accordance with layernya

·         Communication that occurs between

 applications in two computers.

Network devices can

 communicate between each other due to

 these devices run the protocol

 the same stack, even though they

 using different operating systems.

 Data sent from one device running

 down to protocol stack below the

 transmission media, and then rose to

 protocol stack on the opposite side of the device

 communication.

 The figure below illustrates

 how the communication process between the two

 computer.

 In the picture labeled

 X applications and applications Y. When the applications X

 want to communicate with the application of Y

 such as sending messages, the application X will

 asked the OSI layers to make

 relationship with the layers on the computer

 target. This OSI layer communication interaction

 often described as communication between

 peer layer, this means each OSI layer

 can not directly communicate with

 layer on the target computer, but each

 layer has a dependency with

 layer below or above such as layer

 application (layer-7) to make

 relations equivalent to the application layer

 target computer, using

 protocol in the layer. this Prottokol

 requires service on the layer below it

 the presentation layer, and so

 so on each layer will

 requires service on the layer below it

 to the physical layer where this layer

 transmitting the bits through a media

 transmission. Here's the process will be explained more

 much about the process of communication in the OSI.

 Both devices are mutually

 must communicate using a protocol

 the same stack. A message data

 sent from one device to another device

 walk through the process as follows:

  1. Message data is broken down into paketpaket

This is called the prosesencapsulation.

2. Each protocol in the layer

 adds control information

 into packets, enable the features

 such as encryption and error checking. every

 package usually has a component

 follows: Header, Data, and Trailer.

 Header: the header contains

 following information:

 a) Address the origin of the computer

    sender,

 b) Address of the message destination

    sent

 c) Information to synchronize

    clock

Data: Each packet contains data

 which is:

 a) real data from applications, such as

    part of the file sent

 b) The size of 48 bytes of data to the surrounding areas

    up to 4 kilobytes

    Trailer: Trailer package may include:

 a) the information is error-checking

 b) Other control information

    assist the delivery of data

 3. At the physical layer, packets

   converted into a format

   appropriate for electrical

   transmitted.

 4. Protocol at each layer

    related to the device

    opponents (on the receiver side) will

    remove the header and trailer

    added when shipping. package -

 packets are then compiled

 back as the original data.

Advantages and disadvantages of OSI model

The OSI model is very widely used

 in communication networks. It should be

 remember that this is just a theoretical model

 which defines the standards for

 programmers and system administrators

 network. OSI model in its application

 has advantages and disadvantages.

Advantages of the OSI model:

 •  Provide language and references

 the same among fellow professionals

 network

 •  Divide tasks into a network

 logical layers for ease of

 in the development ahaman

 •  Provide flexibility features

 specialized on different levels

 •  Facilitate troubleshooting

 •  Encourage interoperability standards

 between networks and devices

 •  Provide modularity in fiturfitur

 network (developers can

 change features without changing

 with the overall approach)

Disadvantages OSI model:

 •  OSI layers are theoretically and

 in penerapannay not necessarily

 perform functions that

 real.

 •  The implementation of a specific protocol

 can not represent every layer OSI

TCP/IP (Transmission Control Protocol/Internet Protocol)

TCP / IP is a data communications standard used by the Internet community in the process of exchanging data from one computer to another computer on the network the Internet. TCP / IP is an open networking standard that is independent of physical network transport mechanism used, so it can be used anywhere.

The function of each layer in the TCP / IP:

·         Physical Layer

 Bottom layer is a layer that defines the physical quantities such as the communication medium, voltage, current, etc.. TCP / IP is flexible so it can integrate the various networks with the physical medium is different.

·         Network Access Layer

 Has the distribution function set data frames on the physical media used reliably. This layer usually provide service for the detection and correction of errors of data transmitted. Some examples of protocols used at this layer is X.25 public networks, Ethernet for networking Etehernet, AX.25 for packet radio networks, etc..

·          Internet Layer

Having such a function at the Network Layer of the OSI that defines how the relationship can occur between two parties who are on different networks. In this layer duty to ensure that a packet is sent to find the goal wherever located. Therefore, this layer has a particularly important role in realizing the vast territory covering internetworking (Internet worldwide).

·         Some of the important tasks at the Internet layer are:

 a. Addressing

 which complement each datagram to the Internet address of the

 purposes. This protocol addresses the known IP Address.

b. Routing

 Determine to which datagram will be sent in order to achieve the desired goals. This function is the most important functions of the Internet Protocol (IP). Routers on the network TCP / IP is very crucial in the delivery of datagrams from the receiver to the destination.

·         Transport Layer

 Function in defining the ways to perform data transmission between end to end in a reliable host. This layer ensures that the data received with the data that is sent to the sender.

Some essential functions include:

a.  Flow Control

 Delivery of data that has been broken down into packets must be arranged in such a way so that the sender not to transmit data at speeds that exceed the ability of recipients to receive the data.

b. Error Detection

Sender and receiver also complement the data with some information that could be used to check the data transmitted is free from error. If found errors in the received data packet, the receiver will not receive the data. Sender will retransmit data packets that contain errors earlier.

·         Application Layer

 Serves to define applications that run on the network. Protocols at this layer example is SMTP (Simple Mail Transfer Protocol) for sending e-mail and FTP (File Transfer Protocol) to transfer files.

·         advantages:

a.       The existence of the Open Protocol Standard, which is freely available and can be developed independently of the type hadware computer or any operating system that we use. TCP / IP has received broad support from several hardware and software vendors. Thus, it is hoped we can easily connect a wide range of different protocols from different operating system platforms.

b.      There is a High Level Protocol Standard, which can be used to serve users at large, so that computer users can use the existing facilities on the network.

c.        A common method of addressing, so the hardware devices that use the TCP / IP addresses can connect devices to other computers are on the whole network of interconnected computers. It can even also with an external Internet connection.

·         weaknesses:

TCP / IP weakness

 Protection through the use of privileged ports (0000-1000) has little value since the PC has become a client TCP / IP.

     1. There is no priority traffic (easily flood the network).

     2.Lalu traffic can be injected, packets can be stolen or hijacked.

     3. does not offer authentication

     4.TCP (connection based) offer a weak authentication.

     5. No confidentiality (encryption).

·         solutions:

   1.Meminimalkan SYSTEM prior to the time required to empty the connection information from the buffer.

   2.Meningkatkan buffer capacity.

   3.Gunakan Syn-cake method. (This is used in the Linux System)

This is the definition of OSI and TCP/IP according to our group, and the material then we will discuss about the network user application

      NETWORK APPLICATIONS

The working principle of the network protocol TCP / IP is described in outline. Some commonly used applications on a computer network TCP / IP will be presented. Possibility of developing a Wide Area Network (WAN) using TCP / IP in Indonesia will also be explained. For example, the author's experience running a PC in the amateur radio AMPRNet related to the network - the Internet using TCP / IP in Canada will be explained.

Introduction.

Many computer communication protocols have been developed to form a computer network. Competition among computer companies such as DEC, IBM etc.. spawned a variety of standard computer network. This raises difficulties, especially if it will be the interconnection between different types of computers in a wide area.

Around the 70's the Department of Defense (DoD) in the United States pioneered the development of computer network protocol that was not tied to the type of computer or communications media used. Protocol developed called Internet Protocol (at the network layer) [1] and Transmission Control Protocol (the transport layer) [2] or abbreviated as TCP / IP. Various additional protocol was then developed to solve various problems in a TCP / IP. Computer networks using TCP / IP network is now better known as the Internet. It appears that the Internet evolved from the needs and implementation in the field so that these computer networks continue to be refined. Currently TCP / IP is the standard in the UNIX operating system with the included socket library for accessing UNIX programmers directly to the TCP socket. All the standard used on the network TCP / IP can be obtained for free from various computers on the Internet.

In addition to TCP / IP protocol family is actually developed by OSI / ISO as X.25/X.75/X.400 also began to be used by some institutions. Unfortunately all the information about this protocol must be purchased by us to the ISO. This led to development of the ISO / OSI choked unlike TCP / IP. For the longer term, the possibility of TCP / IP will become the world standard computer network. In this article will explain the working principle of the TCP / IP.

Layer protocols in computer networks.

In general, the protocol layer in a computer network can be divided into seven layers. This layer can be seen in Figure 1. From the lowest layer to highest known physical layer, link layer, network layer, transport layer, session layer, presentation layer and application layer. Each layer has the function of each and do not depend on one another.

From the seventh layer is only a physical layer which is the remaining hardware is software. physical layer is a media liaison to transmit digital information from one computer to another computer that physically we can see. Various forms of hardware have been developed for this purpose.

One of them is pretty much used for local computer networks (LAN) in Indonesia is ARCnet is widely used to use Novell software. For the purposes of Wide Area Network (WAN) can we could connect the various LANs are using the medium of radio or telephone into one unit.

To regulate the relationship between two computers through the existing physical layer link layer protocol used. In packet radio networks used in amateur AX.25 link layer (Amateur X.25) X.25 CCITT which is a derivative that is also used in Packet Data Communication System (SKDP) by PT. INDOSAT and PERUMTEL. In the previous article described about <= "" p = "">

IEEE a professional organization for electrical engineering have developed some standard physical layer protocol and link layer for the LAN. Based on the IEEE recommendation on the use of ARCnet LAN (IEEE 802.3) or Ethernet (IEEE 802.3) used link layer (IEEE 802.2). In use Token Ring LAN physical layer (IEEE 802.5). Another form of LAN is less known is the Token Bus (IEEE 802.4). For high-speed LAN also has developed a standard derived from the IEEE 802.3 that became known as the Fiber Distributed Data Interface (FDDI).

This article will focus the discussion on the protocol layer network layer and transport layer. Actually there are several other families protocols in TCP / IP. Shown in Figure 2 in addition to the IP network layer also known as ICMP (Internet Control Message Protocol) [3], ARP (Address Resolution Protocol) [4], and RARP (Reverse Address Resolution Protocol). At the transport layer used UDP (User Datagram Protocol) [5] other than TCP. For a while the discussion will be limited to the working principle of the IP protocols TCP damn. This is because TCP / IP is the protocol most often used in network operations, other protocols are a supplement that helps the network is working. It should be noted that in computer networks using TCP / IP is generally done by the top three layers of the operating system of the computer used. Especially for computers that use UNIX has been available for network programming library so that we can develop your own program with direct access to TCP sockets are available. Maybe on the other opportunity will be explained further on how the TCP socket programming in UNIX that can be accessed using C language

The working principle of the Internet Protocol (IP).

The function of the Internet Protocol can be simply explained as the workings of the post office on mail delivery process. We input a letter to the mailbox will be taken by postal workers and then will be sent through a random route, without the sender and the receiver know the route the letter the letter. Also if we send two letters to the same address on the same day, not necessarily going through the same because it may be a letter that one would take a different route with another letter. In addition, there is no guarantee that the letter would reach the hands of destination, unless we send them using registered mail.

The above principles are used by Internet Protocol, "the letter" above is known as a datagram. Internet protocol (IP) functions deliver a datagram from one computer to another without depending on the medium used kompunikasi. Data transport layer is cut into datagram-datagram that can be carried by IP

Each datagram is removed in a computer network and will find themselves automatically route to be taken to the destination computer. This is known as connectionless transmission. In other words, the computer sending the datagram did not know whether the datagram will arrive or not.

To help reach the destination computer, each computer in a TCP / IP must be given an IP address. IP address must be unique for each computer, but not be an obstacle when a computer has multiple IP addresses. IP addresses consist of 8 bytes of data that has a value of 0-255 which is often written in the form [xx.xx.xx.xx] (xx has a value from 0-255).

In the Internet Protocol header in addition to the IP address of the destination computer and the computer sending the datagram also have some other information. This information includes the type of transport protocol layer is superimposed over IP. Shown in figure 2 there are two types of protocol at the transport layer are TCP and UDP. Other important information is the Time-To-Live (TTL) which determines how long the IP can live on the network. TTL value will be reduced by one if the IP through a computer. This is important mainly because the IP is removed in a computer network. If for some reason could not find the IP address of the destination with the IP TTL will shut itself down when the TTL is zero. Besides, also each given identification IP forwarding so that together with the IP address sending computer data and the destination computer, each IP in the network is unique.

Especially for users of computer networks are the most important thing to understand is the concept really is the IP address. Institutions that set the IP address is the Network Information Center (NIC) in the Department of Defense in the U.S. located at hostmaster@nic.ddn.mil. IP address setting is important, especially when the routing automatically. As an example of a computer network in amateur radio have a class that has the IP address address [44.xx.xx.xx]. Especially for amateur radio in Indonesia the IP address used is [44.132.xx.xx]. While writers in Canada have an IP address [44.135.84.22]. It is seen clearly that the IP address in the amateur radio geographical nature. IP addresses of authors can be read that the author was in the machine 44 in the Internet network, known sabagai AMPRNet (ampr.org). 135 signifies that the author was in Canada. 84 tells us that the author was in the city of Waterloo in Ontario province, while 22 is the number of machines the author. With the concept of IP addresses, IP traveled route in the computer network can be done automatically. For example, if a computer on the Internet will send the IP to [44.135.84.22], first released in the IP network will try to find a way to network 44.135.84, after the networks that connect machines 44.135.84 reached the IP will attempt to contact 22 machines in the network. All this is done automatically by the program.

Surely it is difficult for humans to remember so many IP addresses. For ease, developed the Domain Name System (DNS). For example, authors in AMPRNet machine with the IP address [44.135.84.22], the authors give the name (hostname) ve3.yc1dav.ampr.org. Seen that the hostnames are used writer is very specific and very easy to learn that the author was in AMPRNet of ampr.org said. The machine was located in Canada and the provinces of Ontario currently YC1DAV ve3 is a writer himself. Another example of the DNS is sun1.vlsi.waterloo.edu which is a Sun SPARC workstation (sun1) in the VLSI research group at the University of Waterloo, Canada (waterloo.edu) where the author's work and learn. It should be noted that the current NIC domain not given to Indonesia. Hopefully with the development of computer network TCP / IP in Indonesia there are times when we in Indonesia have asked for a separate domain for Indonesia

·         The working principle of the Transmission Control Protocol (TCP).

Unlike the Internet Protocol (IP), TCP has a working principle as a "virtual circuit" on the telephone network. TCP is more concerned with know-how and reliability in data transmission between two computers in the network. TCP does not care what is done by IP, which is important is the communication link between two computers running well. In this case, the TCP setting out how to open links of communication, what kind of applications will be done in such communications (eg sending e-mail, file transfer, etc..) In addition, it also detects and corrects data errors if any. Manage the entire process TCP connection between one computer to another computer within a computer network.

In contrast to the connectionless IP mechanisms that rely on the TCP connection is a connection oriented mechanism. In this case, the logical relationships to be built by TCP from one computer to another computer. In a specified time a computer that is connected to send data or acknowledge that the relationship continues. If this is not done then it could be assumed that the computer is in contact with us to crash and logical relationships may be terminated.

TCP multiplexing set of data sent / received by a computer. The identification of the TCP header allows the multiplexing performed. This allows a computer to do some logical TCP connection. Form of relationship is full duplex, this allows two computers talk to each other in the same time without having to take turns using the channels of communication. To overcome the saturation (congestion) on the communication channel, in the TCP header has information about flow control.

It is quite important to understand the TCP port number is. Port number to determine the services performed by application programs over TCP. These numbers have been determined by the Network Information Center in the Request For Comment (RFC) 1010 [10]. As an example for the application File Transfer Protocol (FTP) over TCP transport layer used port number 20 and many more.

The working principle of the TCP based client-server principle. Server is a program on a computer that will passively listen (listen) port number specified in the TCP. 're Client is a program that actively opens a TCP connection to the server computer to request the services needed.

Working TCP state diagram shown in Figure 3. In the state diagram of figure 3, the client will actively open a connection (active open) by sending a SYN signal (SYN Sent state) to a destination server computer. If the server receives the SYN signal the server when it is in LISTEN state will send a signal SYN and the two computers (client & server) going to the ESTAB state. If no response from the destination computer, then the program will return to the state CLOSE. Once the service is performed has been completed then the client will send the wrong signals FIN and client computers will be in state FIN FIN WAIT until the signal is received from the server. On receipt of a signal FIN, the server will be to the state CLOSE WAIT until the connection is disconnected. Finally, both computers will be back on the state CLOSE.

Some examples of applications of the Internet.

Many applications are possible using a family of TCP / IP. Typical applications are electronic news delivery, known as electronic mail (e-mail). It developed a protocol for Simple Mail Transfer Protocol (SMTP) [6]. The protocol sets out procedures for transmitting messages from a user on a computer to another using a unique address. For example, e-mail me at AMPRNet are:

yc1dav@ve3.yc1dav.ampr.org

which means that the author YC1DAV was in (at, @) ve3.yc1dav.ampr.org machine. Certainly at the time of delivery of news, the IP will do the conversion of hostnames to IP addresses ve3.yc1dav.ampr.org author [44.135.84.22] to then send the information to be included in the SMTP protocol TCP.

Another application is the remote login to a remote computer. This is done by using the Telnet facility [7] that runs above the TCP transport layer. To perform file transfers use File Transfer Protocol (FTP) [8] which is also run over TCP. With the growing complexity of the network, network management becomes important. Currently developed a special protocol to be used to manage the network with the name of the Simple Network Management Protocol (SNMP) [9]. There are many other applications that run on top of TCP, such as NNTP, etc. RSPF. Each application has a unique TCP port number.

One thing is quite interesting with the use of TCP / IP is the possibility to connect multiple computer networks using different communication media. In other words, the computer connected to the network using ARCnet, Ethernet, Token Ring, SKDP, amateur packet radio, etc.. can talk to each other without knowing each other that the medium of communication used is physically different. This makes it possible to easily form a Wide Area Network in Indonesia. Currently UNINET pioneered by colleagues from the UI feels PUSILKOM-faltering mainly because of the high cost that must be spent for communication. In addition, the protocol used in networks today is the UUCP UNINET which is basically a very simple protocol. It is not possible UNINET to do things that are only possible for TCP / IP such as automated network management using SNMP and relationships as it is done using a connectionless IP.

To further clarify, it's good real world examples the authors put forward by the author in amateur packet radio network (AMPRNet) in Canada. Broadly speaking, computer network topology packet radio amateurs in Waterloo shown in Figure 4. Currently AMPRNet network in Waterloo working on The frequency of 145.09MHz at 1200bps speed. We plan for upgrading the network TCP / IP available to the speed of 9600bps. In the picture's written some of the machines of friends and writers such as at.ve3euk.ampr.org home.ve3rks.ampr.org.

Here we have a gateway at.ve3uow.ampr.org's University of Waterloo - Amateur Radio Club (ARC UoW), which the authors are also members, is the gateway connecting networks AMPRNet with Token Ring LAN PC network at the University of Waterloo. Through a gateway that is in Token Ring networks, the IP is sent by the machine in AMPRNet may be associated with the Unix machines on an Ethernet network at UoW or with other machines on the Internet. Not much between AMPRNet and Internet gateways that operate in the world today. It can be seen in the previous article the author about the author's experience working in amateur packet radio networks abroad.

At Waterloo we use sunee.waterloo.edu AMPRNet and watserv1.waterloo.edu as domain name server (DNS). In other words, using the protocol UDP / IP AMPRNet machines at Waterloo if it would relate to other machines on the Internet that hostnamenya AMPRNet or known to ask for the IP address of the destination machine to the DNS. All this is done automatically without the need for machine operators know the process occurs.

With the amateur packet radio technology in the world of amateur radio. The chances of developing low-cost WAN in Indonesia became possible. UNINET AMPRNet because it is not possible using amateur packet radio knows no UUCP. Even if forced amateur radio should be required to develop software from scratch. The use of TCP / IP will make it easier internetwoking with various networks like AMPRNet that ultimately opens the possibility of developing WAN costs easy, but with much better facilities than the UUCP.

Additional Duties:

 1. transmission of data from the topology?

 2. difference between windows server and linux servers?

 3. differences in LAN, MAN, WAN?

 4. tree topology, multilevel what?

1.     Factors to consider when selecting a topology

·         Cost – whatever transmission medium is chosen for a Local Area Network has to be physically installed in the building, this maybe a lengthy process including the installation cables and raceways. For a Network to be cost effective one would strive to minimize installation costThis may be achieved by using the proper hardware linking the cables, good modems, cost effective computers to reduced cost

·         Flexibility – one of the main benefit of a local Area Network is it ability to have the data processing and peripheral nodes distributed around a given area. This means that the computing power and equipment can be located close to the ultimate users. Because the arrangements of furniture, internal walls etc in the offices is often subject to change. The topology should allow for easy reconstruction of the network which involves moving existing nodes and adding new nodes.

·         Reliability – The topology chosen for the network can help by allowing the location of the fault to be detected and to provide some means of isolating the faults

Data Transmission

Data Transmission success depends on:

               1. The quality of the transmitted signal

               2. Characteristics of transmission medium

                   The types of Transmission media:

                               a. Wire open / open wire

                               b. Cable double interlace / twisted pair cable

                                   Consists of two copper wire insulation

                                   arranged in a spiral that is protected.

                                   These rolls minimize interference between

                                   cable. Used to be used on the system

                                    telephone, for long distances with data

                                    rate of 4 Mbps or more, low cost.

                                   Has the lowest bandwidth.

                               c. Coaxial cable

                                   Consists of conductors outside the cavity cilinder

                                    around a single conductor wire,

                                    two conductors separated by insulating material.

                                    Used for telephone transmission and

                                     television remote, television distribution (TV

                                     cable), local area networks, short-run system

                                     links.

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3.      Local Area Network (LAN), a privately owned network within a building or campus-sized to several kilometers. LANs are often used to connect personal computers and workstations in a corporate office or factories in order to use shared resources (resouce, such as printers) and exchange information.

· Metropolitan Area Network (MAN)

Metropolitan Area Network (MAN), basically a LAN version of the larger and usually use the same technology to the LAN. MAN can include corporate offices are located adjacent or also a town and can be used for private purposes (private) or public. MAN capable of supporting data and voice, even may be associated with cable television networks.

· Wide Area Network (WAN)

Wide Area Network (WAN), the range covers a wide geographical area, often covering a country or even continent. WAN consists of a collection of machines that aim to run the programs (applications) user.

4.

Network Topology Tree (Tree) network topology is referred to as a multilevel network topology. This topology is typically used for interconnection between different central denganhirarki. For the lower hierarchy depicted in locations with low and growing up had a higher hierarchy. This type of network topology suitable for use on a computer network system.

 In tree networks, there are several levels of nodes (node​​). Central or higher level node, another node can set a lower level. Data sent to the central node first. For example to move from computer to kekomputer node node-3-7 as well as in the figure, the data must pass through node-3, 5 and node-6 before ending at the node-7. Keungguluan network tree model like this is, can the formation of a group that is required at all times. For example, companies can form a group consisting of terminal accounts, as well as in the other group formed for the sale terminals. The drawback is, if the node that is higher then does not work, then the other group who are below it eventually also became ineffective. The workings of a tree network is relatively slow.