PROGRAM STUDI Management
Bina Sarana Informatika
Data communication is the process of sending information between two points using the binary code
passes the transmission line and switching equipment can occur between the computer and the
computer, the computer terminal or computer equipment. Data communication is a combination of
telecommunications engineering data processing techniques.
Communication is very important in our daily lives, so that we can mutually Interact with others.
When we Communicate, we share information. This sharing can be done locally or remotely.
Between individuals, local communication is usually the case with face to face, while remote
communication takes place from a distance. Terms of telecommunications, the which includes
telephone, telegraph, and television, means of communication at a distance (in Greek Tele meaning
'far'). So is the computer, in the which we Often the make the process of sending and receiving of
data from one computer to anotheris commonly Referred to as the data communications.
Keywords: Communications and Networks, Communications and Processing
Purpose Data Communication.
• Allows sending large amounts of data efficiently, without errors and economically from
one place to another.
• Allows the use of computer systems and support equipment (remote computer use)
• Allows the use of a centralized computer system and are dispersed so that support the
management in terms of control (either centralized or decentralized)
• Facilitate the possibility of managing and regulating the existing data in a wide variety of
• Reduce time for data processing.
• Obtain data directly from the source (enhances reliability).
• Accelerating the dissemination of information.
Basically, data communication is the process of sending data from one computer to another. To be
able to transmit data on a computer should be added a special tool known as a network interface
This type of network interface varies depending on the physical medium used to transfer data.
Another thing to note is on the computer, the data transfer destination there may be more than one
application is waiting for data. The data must be sent to the appropriate application, the right
computer without errors.
For any problem in data communications, created a special solution in the form of rules to deal with
such problems. To handle all the data communication problems, overall this rule must cooperate with
each other. A set of rules to regulate data transmission process is referred to as a data
communication protocol. This protocol is implemented in the form of computer programs (software)
contained on the computer and other data communications equipment.
Data Communication Model
Data communications relating to the exchange of data between two devices directly terhubuang
which enables the exchange of data between the two parts. Figure 2.1 illustrates the data
Figure 2.1 Data Communication
In figure 2.1 are the key elements in the model:
• Source (source): This tool generate the data that can be transmitted, for example telephone,
Personal Computer (PC)
• Transmitter (sender): Usually the data generated from sources sister ditransmisikansecara not
directly in its original form. A transmitter is quite moving, and marking information in the same
way as electromagnetic signals that can be transmitted over multiple sequential transmission
• Transmission system: Form of a single transmission line (single transmission) or jarinagn
complex (complex network) that connects the source to the destination (destination).
• Destination (destination): capture data generated by the receiver
Based on the background of the above problems, the authors are interested in researching this
field to take the title "Application of Modulation Techniques In Data Communications.
The computer network is a collection of computers, printers and other equipment
connected. Information and data moving through wires allowing
computer network users can exchange documents and data, print on
the same printer and together using hardware / software that is connected
the network. Each computer, printer or peripherals connected to the network
called nodes. A computer network can have two, tens, thousands or even
millions of nodes.
A network typically consists of 2 or more interconnected computers
among one another, and share resources such CDROM,
Printer, exchange files, or allow it to communicate with each other
Type - Type Network
There are three types of networks:
1.Local Area Network (LAN)
LAN is a network that is limited by the relatively small area, generally limited
by the environment such as an office area in a building, or a
school, and usually not far from approximately 1 square km.
2. Metropolitan Area Network (MAN)
MAN usually covers a larger area than a LAN, for example between regions
within a province. In this case the network connecting several pieces
small networks into larger areas of the environment, for example
namely Bank network where some branches of a bank in a big city is connected between one and
3. Wide Area Network (WAN)
Wide Area Networks (WAN) is a network whose scope usually already
by means of satellite or submarine cable as an example of a whole network of BANK BNI in
Indonesia or in countries.
Source: Materi Kuliah Bina Nusantara
a.LAN (Local Area Network)
LAN is used to connect a computer that is located in a small area, such as in an office building or
campus. The distance between the connected computers can reach 5 to 10 miles. A LAN bias works
at speeds from 10 Mbps to 100 Mbps sampi. LANs are becoming popular because it allows multiple
users to use the resources that you can use it for example a mainframe, file servers, printers, and so
b.MAN (Metropolitan Area Network)
MAN is a network whose scope covers a city. MAN connects LANs, which are located far apart.
MAN range up to 10 miles to several hundred miles. A MAN usually work at a speed of 1.5 to 150
c.WAN (Wide Area Network)
WAN is designed to connect computers located on a broad geographic scope, such as the
relationship from one town to another within a State. WAN coverage bias covering 100 km to 1,000
km, and regular inter-city speed varies between 1.5 Mbps to 2.4 Gbps. In the WAN, the cost of
equipment for high-speed transmission, and WAN networks typically owned and operated as a public
Computer Networking: Computer Network
TopologyTopologi describe the structure of a network or how a network is designed. This pattern is closely
associated with the method of access and delivery of media used. Topology that is highly dependent on the
location geofrapis of each terminal, the quality control required in the communication or delivery of messages,
as well as the speed of data transmission. In the definition of the topology is divided into two, namely the
physical topology (physical topology) which indicates the position of the physical cabling and logical topology
(logical topology) which shows how a media accessible by the host.
Network topology there are several forms as follows.
• Bus Topology
This topology is the initial topology is used to connect a computer. In this topology each computer will be
connected to a long cable with multiple terminals, and at the end of the Kable must end with a terminator. This
topology is very rarely used in building a network of regular computer because it has several shortcomings
including the possibility of its collision data stream, if one device is broken or there is damage to one part of
the computer directly connected network will not work until the damage to be overcome.
This topology Coaxial Cable initially used as a medium of instruction data and information. But at the moment
this topology in the build kabal computer network using optical fiber (fiber optic) but combined with other
network topologies to maximize performance.
• Ring Topology
Or extending the ring topology is often called the ring topology is a network topology where each computer
connected in a circle. With a sense every computer that is connected into a network of inter-connected to two
other computers to form a network similar to the shape of a ring.
The advantages of this topology is the cable that is used can be saved. The downside of this is the development
of a network topology will be difficult because each computer will be connected.
• Token Ring Topology
This topology is similar to a ring topology but making more refined. Can be seen from the difference image.
In the picture clearly shows how the token ring Kable made into a circle connecting the first and will
be in to back the terminals for each of the computers and other devices.
• Star Topology
Or star topology is more often called star topology. In this topology we have to use another tool to
help connect computer networks. Examples of tools in use here is the hub, switch, etc.
In the visible image of the hub serves as a hub of computers interconnected. The advantage of this topology is
very much all of which facilitate network administrators to manage, facilitate the addition of a computer or
terminal, ease of detecting defects and errors in the network. But with many of its advantages in terms of
topology is not without flaws. Shortcomings include waste to cable, control centered on the hub so sometimes
critical problems that in case of damage to the hub, then all of the network will not be in use.
• Topology tree
Or tree topology also called hierarchical topology and can also be called multilevel topology is a
topology that can be used on the network in the multi-storey office space.
In the picture we can see the relationship between one computer to another computer with a branching
hierarchy or central jelas.sentral which is at the very top of an active central central while underneath is a
Public Data Network (PDN); Network used to connect a network hub with each other and
are usually located far apart even be on another continent. The central general of PDN
possession of the government or other organizations.
Private Branch Exchange (PBX); Network which is used primarily for telephone or voice
communication on the buildings but uses the same technology as the telephone exchange.
Similar to the LAN but the data transfer is not as high as its LAN.
3. Data Communications Hardware
The equipment used to perform the interaction / communication distinguished above
(equipment inter action):
a. Data Communication Equipment - DCE, to distribute information between locations.
b. Data Terminal Equipment - DTE, the equipment where entry and exit information for
users and computers.
In the existing system data communication system that governs the relationship with the
data communications equipment. This equipment is called Data Communication Controller
Unit - DCCU.
The task of DCCU among others:
Establish an interface between the system input / output bus and a modem;
Controlling modem interface signals and converting the signal level to match the
Change the data to be transmitted into the series and vice versa;
For synchronous equipment are buffers, and control of news between the two
stations is done by DCCU;
Set the error recovery to retry mechanism;
Perform code conversion where necessary;
Perform synchronization good character by means of start / stop and the SYN
Conduct bit synchronization for asynchronous controller. Sometimes synchronous
controller can also do it with the internal clock;
Perform testing error (parity, longitudinal or BCC);
Controlling procedures to track the transmission control character.
Included in the classification DCCU include the I / O controller and the controller
Terminal is the location in the network which is where the information can get in and out.
Thus a computer can be classified as a terminal, when the function is indeed the case.
Some common kinds of terminals:
Key board - printer
Key board - a video display
Benefits of Data Communication Network
1. Allows multiple computer systems sharing (sharing) resources together
So it is economical.
2. Adding the benefits of the computer as a network expands the usefulness and usability of
computer systems that are connected to the network so that the terminal with the terminal can
communicate, exchange data, and can replace the function of correspondence.
3. Allows a variety of brand computers interconnected, thus users do not
depending on the vendor / seller.
4. Allow the development of computer systems are relatively easier and causes the system
computers become more flexible.
5. The distributed processing, so as to prevent dependence on the center or central
processor or not depending on a single computer system.
6. Allows the integration of a wide variety of applications that run on a variety of systems
computer. The data generated by one part can be immediately used by other departments and vice
Cycle Data Processing
Derived from the word processing if that means a series of activities or conducting activities - specific
activities for specific activities as well. Based on the understanding that the processing of data is a
series of activities, thoughts and energy assistance or an equipment which follow a series of steps,
the formulation of such data, form the composition, the nature or contents become more useful. Data
processing can be done in centralized and decentralized. Sentaralisasi data processing allows
a. Application of the division of labor with the division of costs and quantitative development more
b. Use the same file on a lot of data processing.
c. A better utilization of technical administration of the target.
d. Application of separation of functions between operational and central data processing.
Data processing can be interpreted also as all the processing to make the data useful in accordance
with the desired result that can be immediately used. Data processing is a process of receiving data
as input (input) and processed (processing) by a particular program and issued the results of data
processing by computers is known a system called EDP (Electronic Data Processing) is a data
processing system in which computers play a major role.
Judging from the data processing system, can be divided into three basic phases, namely:
a. Read data or input data.
b. Process data or process
c. Results or outputs.
Data through computer processing includes several sections, among others:
Data were processed and written in a basic form of further data processing.
Giving an identification into processed data, the classification that is often made is code such as
numeric, alphanumeric, and so on.
Once the data to be processed are identified, the data needs to diataur / sorted according to its
classification code and usually sorted according to their numeric code.
4. Calculating (counting)
Implementation of the calculation is needed in calculating the data in and data out.
5. Storing (storage)
Similar data storage in the form of reference that will come to be done. The period of data storage
each data differ among one another.
6. summarizing (compilation)
To enable the analysis of the data or information that is generated, it is necessary to manufacture
recapitulation report liking the needed information.
7. Retrieving (Search)
Search data into a file or stored distore consists of several ways adapted to storage.
8. reproducing (Distribution)
The data can be reproduced owned liking, doubling can be done with a photo copy.
9. Distribute (Distribution)
In data processing, information generated from several parts that held the division of the report.
The Internet is a computer network that is very open in the world, the consequences
which should be on the responsibility is no guarantee of security for the network related to
The Internet. This means that if network operators are not careful in setting up the system, then
most likely related to the Internet network will be easily accessible people
were not invited from outside. It is the duty of the relevant network operator,
to suppress these risks to a minimum. Selection strategies and skills
The network administrator, will be very easy to distinguish whether a network
penetrated or not.
Firewall is a tool to implement the security policy (security
policy). While the security policy, based on the balance between facilities
supplied with its security implications. The more stringent security policies,
increasingly complex service configuration information or the fewer facilities
available on the network. Conversely, with more and more facilities are available or
applied in such a simple configuration, the easier people
'Nosy' from the outside into the system (a direct result of the lack of security policy).
In the real world, a firewall is a wall that separates the room, so that
fire in a room does not spread to other rooms. But the truth
firewall on the Internet is more like a defense around the castle, which maintains
against attacks from outside. Point:
• restrict the movement of people into the internal network
• restrict the movement of people who come out of the internal network
• prevent attackers layered defense approach
So that out of the firewall should be acceptable. A firewall is a combination of
routers, servers, and appropriate complementary software.
A firewall is a method / system / mechanism is applied both to
hardware, software or system itself with the aim of protecting, either
by filtering, limiting or even reject any or all relationships / activities
a segment of the private network to the outside network that is not a space
scope. These segments can be a workstation, server, router, or
local area network (LAN).
Source: Free Articles (Firewall)
Firewall is defined as a component or set of components that
restrict access between a protected network and the Internet, or between
clusters of other networks (Building Internet Firewalls, by Chapman and
Zwicky). A firewall is a system or group of systems that enforces an access control policy
between two networks (http://www.clark.net/pub/mjr/pubs/fwfaq/). The main purpose of a
firewall system is to control access to or from a protected network. It implements a
network access policy by forcing connections to pass through the firewall, where they can
Be Examined and evaluated (http://csrc.ncsl.nist.gov/nistpubs/800-10/node31.html).
2.2.1 Task - Task Firewall
Firewalls generally at designated to serve:
• Engineering / Computers
Every machine that is connected directly to a computer outside the network or the Internet and
wants all contained in the protected computer.
Computer network consisting of more than one computer and various types
network topology, both owned by the company, organization
Firewall has several tasks:
• First and foremost is: must be able to implement policies
security in the network (site security policy). If a particular action is not allowed by
This policy, then the firewall must ensure that all businesses that represent
The operation should fail or be defeated. Thus, all the illegal access
inter-network (not authorized) will be rejected.
• Perform filtering: requiring all existing traffic to pass through
firewall for all the process of granting and utilization of information services. In The
this context, the flow of data packets from / to the firewall, selected based on their IP address,
port number, or direction, and adapted to the security policy.
• Firewall should also be able to record / record suspicious events and
notify the administrator against any attempts to penetrate policy
There are some things that can not be done by the firewall:
• Firewalls can not protect against insider
• Firewalls can not protect against that is not through the firewall (not
through chocke point). For example, there are installing a dial-up service, so
network can be accessed via a modem.
• Firewalls can not protect the internal network against attacks models
• Firewalls can not protect the network against viruses.
Source: Free Articles (Module Personal Firewall)
1. The whole relationship / activities from the inside out, must pass through the firewall. This matter
can be done by blocking / physical limit all access
to the local network, but pass through the firewall. There are many types of network
2. Only the registered activity / known that can pass / intercourse,
this can be done by adjusting the local security policy configuration.
Many types of firewalls that can be selected at the same time various types of policy
3. The firewall itself must be immune or relatively robust against attacks / weaknesses.
This means the use of a system that can be trusted and the operating system
Techniques Used Firewall
1. Service Control (control of the service)
Based on the types of services used on the Internet and can be accessed either
into or out of the firewall. Usually the firewall will check no IP
Address and port number in use both TCP and UDP protocols,
can even be fitted to the proxy software that will receive and
translate each request will be a service before allowing.
It could even be the software on the server itself, such as services for the web and
2. Direction Conrol (control of direction)
Under the direction of the various requests (request) to the services that will
recognized and permitted through the firewall.
3. User control (control of the user)
Based on the user / user to be able to run a service, meaning that a user
which can and there are not able to run a service, it is in because
The user is not allowed to pass through the firewall. Typically used for
restrict users from the local network to access the exit, but can also
applied to restrict the user to the outside.
4. Behavior Control (control of treatment)
Based on how many services it has been used. For example, the firewall can
email filtering to mitigate / prevent spam.
Type - Type Firewall
1. Packet Filtering Router
Packet filtering is applied by arranging all the good IP packet
toward, past or will be addressed by the packet. In this type of packet is
will be set if be received and forwarded or rejected. Packet Filtering
is configured to filter the packets to be transferred in both directions
(Both from and to the local network). Filtering rules based on IP header and
transport header, including the initial address (IP) and destination address (IP), the protocol
transport that is in use (UDP, TCP), as well as the port number used. Excess
of this type is easy to implement, transparent to the user,
The weakness is pretty complicated for setting up a packet to be
filtered appropriately, and weak in terms of authentication. The attack can be
occurred on the firewall with this type are:
• IP address spoofing: Intruder (intruder) from outside can do this with
I include / use local network IP addresses that have been permitted
for through the firewall.
• Source routing attacks: This type does not analyze the IP source routing information,
making it possible to bypass the firewall.
• Tiny Fragment attacks: Intruder IP divide into parts (fragments)
Smaller and forced division of the TCP header information.
This type of attack is designed to deceive the filtering rules that depend
the information from the TCP header. Attackers expect only a part (fragment)
The first course to be in check and the rest will be able to pass freely. Case
This can be in the tackle by rejecting all packet with TCP protocol
and has offset = 1 IP fragment (IP section)
Source: Free Articles (Ammar-Firewall)
2. Application-Level Gateway
Application-level gateway which is also commonly known as a proxy server that serves
to strengthen / channel flow applications. This type will arrange all relationships
who uses the application layer, either the FTP, HTTP, GOPHER etc.
The way it works is if there are users who use one application
such as FTP for remote access, then the gateway will ask the user
enter the address of the remote host will be in akses.Saat user sends the user ID
as well as any other relevant information, the gateway will perform on the relationship
The application contained on the remote host, and distribute data between the two
full stop. If the data does not match then the firewall will not forward the data
it or reject it. Furthermore, in this type of firewall can be configured
for only a few applications support only and rejected other applications
pass through the firewall.
The surplus is relatively safer than the type of packet filtering routers easier
to check and log all incoming data streams at the application level.
The drawback is that excessive additional processing on any relationship. Which
will result there are two connections between the user and the gateway connection,
where the gateway will check and forward all of the two-way flow.
Planning the Network With Fireawll
Plan a firewall system on the network, closely related to the type of facility
which will be provided to the users, the extent of the risk-level of security that can
received, as well as how much time, money and expertise are available (technical factors and
economical). Firewalls generally consists of the filter (also called screen or choke)
and part of the gateway (gate). Filter function to restrict access, narrow canals,
or to block certain traffic classes.
The access restrictions, will reduce the network function. To stay
maintaining a network of communication functions within the air-firewall, generally
taken two ways:
• First, if we imagine we are in a protection network a
fort, communication can occur through the doors of the castle exit. Way
This is known as a packet-filtering, where the filter is used to reject
traffic on the unused channel or channels with sufficient security exposures
large, while the other traffic on the canal is still allowed.
Policies can be applied to perform packet filtering operations. At The
Essentially, in the form of a data level controlled by a mechanism that is allowed to flow from
and / or to the internal network, using several parameters
listed in the header of a data packet: direction (inbound or outbound), address the origin and
destination, the port of origin and destination, as well as the type of transport protocol. The router will
The information in each packet of data that flows through it, then
specify the action to be performed on the package, based on the set
rules / program in the packet-filtering. So the basic router routing decisions
these, then fitted with a part of the network security policy.
• The second way, using the proxy system, where each communication that occurs
between the two networks should be done by an operator, in this case the proxy
server. Some protocols, such as Telnet and SMTP (Simple Mail Transport
Protocol), will be more effectively dealt with the evaluation of the packet (packet filtering),
while others such as FTP (File Transfert Protocol), Archie, Gopher and
HTTP (Hyper-Text Transport Protocol) will be more effectively dealt with by the system
Proxy. Most firewalls use a combination of these two techniques (packet
filtering and proxy).
In a network that implements the proxy system, communication links to the internet
conducted through a system of delegation. Computers that can be recognized
by the Internet acts as a 'representative' for the other machines that want to connect to
outside. Proxy server (set) of certain protocols are run on a dual-homed
bastion host or host, where all network users can communicate
to him, then the proxy server acts as a delegate.
In other words each client program to be associated with the proxy server and proxy servers
who will be in touch with the real server on the internet. Proxy servers will
evaluate each request from the client relationship and decide which one
is allowed and what is not. When this connection request is approved, then the
proxy server relays the request to the real server.
From the above discussion, the authors conclude that the data communication is very beneficial for
humanity and life in the fields of education, social, economic and also as a means of entertainment,
especially for the advancement of science and technology.
Data Communications also has many applications menyuguhkam various advantages and
convenience for users.
Let us be wise in all things, including the use of activity modulation techniques and data
communication in the network components in the computer. If we use the internet properly it will help
us in the work. Conversely, if we use for the bad things that would harm ourselves or others.
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