Redes

The Communication Networks (Las Redes de Comunicacion)


1. Introduction


Communication networks are nothing more than the possibility of a universal sharing of information between groups of computers and their users, a vital component of the information age. Widespread computer or personal computer (PC) and local area network (LAN) during the eighties has led to the ability to access information in remote databases, load applications from overseas points, send messages to other countries and share files, all from a personal computer. The networks that allow this are advanced and complex equipment. Its effectiveness is based on the confluence of many different components. The design and implementation of a global network of computers is a major 'technological miracles' of recent decades.


2. Concept Network

It is a set of physical devices hardware and software "software", by which computers can communicate to share resources (disks, printers, software, etc..) And (time of calculation, data processing, etc.). . Each of the computers connected to the network is called a node. Network is considered local if it only reaches a few kilometers.

3. Types Of Networks

Information networks can be classified by their size and topology. A small network can start to grow with the organization or institution. Below is the different types of networks available:

Extension According to geographical distribution:

Network segment (subnet) :

A network segment is usually defined by the hardware or a specific network address. For example, in the environment "Novell NetWare" on a network segment includes all workstations connected to a network interface card on a server and each segment has its own network address.

Local area network (LAN) :

A LAN is a network segment that is connected workstations and servers or a set of interconnected network segments, usually within the same area. For example a building.

Campus Network

A campus network is extended to other buildings within a campus or industrial area. The various segments or LAN in each building are connected by network cables support. Metropolitan area network (MAN) A MAN network is a network that spreads by towns or cities and are interconnected by various public or private facilities such as telephone system or the suppliers of microwave communication systems or optical media.

Wide Area Network (WAN and global networks)

WANs and global networks extend beyond the borders of cities, towns or nations. The links are made public telecommunications facilities and private, in addition to microwaves and satellites.

4. Topology

The topology or logical form of a network is defined as the way to build the cable to individual workstations, for walls, floors and ceilings of the building. There are a number of factors to consider to determine which topology is most appropriate for a given situation. There are three common topologies:

"Ring"

The stations are linked to each other in a circle through a common wire (Figure 1). The last node of the chain is connected to the first closing the ring. The signals traveling in one direction around the circle, regenerating at each node. With this approach, each node examines the information that is sent through the ring. If information is not directed to the node that the review, go to the next in the ring. The disadvantage of the ring is that if a connection is broken, the entire network goes down.

Figure 1

"Star"

The network joins a single point, usually with a centralized control panel, as a hub for wiring (Figure 2). The blocks of information are routed through central control panel to their destinations. This scheme has an advantage to have a control panel that monitors the traffic and avoid collisions and a broken connection does not affect the rest of the network.

Figure 2

"Bus"

The stations are connected via a single cable segment (Figure 3). Unlike the ring, the bus is passive, there is no regeneration of signals at each node. The nodes in a network of "bus" transmit information and hope it will not collide with other information transmitted by another node. If this happens, each node waits a short amount of time at random, then tries to relay information. Figure 3

• Hybrid

The linear bus, star and ring sometimes combine to form combinations of hybrid networks (Figure 4).

* Star Ring

This topology is used in order to facilitate network administration. Physically, the network is a central star in a hub, while logical level, the network is a ring.

* "Bus" star

The order is equal to the previous topology. In this case the network is a "bus" to be physically wired as a star through hubs.

* Hierarchical Star

This structure cabling is used in most existing local networks through hubs pair arranged in cascade form a hierarchical network.

Figura 4

5. Network Protocols

A network protocol is like a language for communication of information. Are the rules and procedures used on a network to communicate between nodes that access the cable system. The protocols govern two levels of communication:

The high-level protocols: These define the way applications communicate.

The low level protocols: These define how signals are transmitted by cable.

As usual in the case of computers constantly changing protocols are also constantly changing. Currently, the most commonly used protocols in the networks are Ethernet, Token Ring and ARCNET. Each of these is designed to provide some kind of network topology and have certain standard features.

Ethernet

Currently the protocol is easy and inexpensive. Use the topology of "Bus" linear.

Token Ring

The network protocol is the IBM token ring, which is based on ring topology.

Arnet

It is based on the star or star topology distributed, but has a topology and protocol.

6. Network devices

NIC / MAU (Network Card) "Network Interface Card (network interface card) or" Medium Access Unit (Medium Access Unit). Each computer needs the hardware to transmit and receive information. This is the device that connects other computer network computadorau with the physical environment. The NIC is a type of expansion card from the computer and provides a port on the back of the PC to which it connects the network cable. Today more and more computers with network interface, primarily Ethernet incorporated. It is sometimes also necessary network card, a transceiver. This is a device that connects to the physical environment and the card, either because it is not possible direct connection (10 base 5) or because the medium is different from that to the card.

Hubs (concentrators)

These are computers that allow structured cabling networks. The variety of types and characteristics of these teams is great. At first there were only wiring hubs, but have increasingly greater number of network capacity, remote management, etc. The trend is to incorporate more functions in the hub. There are hubs for all types of physical media.

Repeaters

Teams are physically active. Prolong the length of the network by joining two segments and amplifying the signal, but with it also amplify the noise. The network remains a single, which still apply the limitations on the number of stations that can share the medium.

"Bridges" (Bridges)

Are teams joining two networks operating on low-level protocols at the level of media access control. Only network traffic that is directed to the other through the device. This allows administrators to divide the networks into logical segments, relieving traffic interconnections. Bridges produce signals, thus noise is not transmitted through them.

Routers (Router)

They are networking equipment operating at the level of network protocols. Can use different interconnection systems improve the efficiency of transmission between networks. Its operation is slower than bridges but its capacity is greater. Allow even link two networks based on a protocol by one using a different protocol.

"Gateways"

Teams are to interconnect networks with completely different protocols and architectures at all levels of communication. The translation of the information units greatly reduces the transmission rate through these devices.

Servers

These are computers that allow connection to the network of peripheral equipment for both input and output data for. These devices are offered in the network as shared resources. Thus a terminal connected to one of these devices can establish sessions against several multi-user computers available on the network. Similarly, any system on the network can print to printers connected to a server.

Modems

These are computers that enable computers to communicate with each other over telephone lines, modulation and demodulation of electronic signals that can be processed by computers. Modems can be external (communication device) or internal (internal communication device or circuit board that is inserted into an expansion slot of the computer).

The development of information technology.

The Information Technology has been conceptualized as the integration and convergence of computing microelectronics, telecommunications and technology for data processing, its main components are: the human factor, the content of information, equipment, physical infrastructure , software and mechanisms for electronic exchange of information, elements of policy and regulations and financial resources.

Is the information between computers, integrated services digital networks, satellite transmission and trans-border data flow global problems of mankind and a serious political issue of unpredictable social and economic conscience?.

If we examine these components we realize that are the major players in software development in a society for their development both as to its implementation also recognizes as information technologies are the core of a multidimensional transformation experienced by the economy and society, hence the importance of the study and mastery of the influences that such a transformation requires humans as social beings, as it tends to change not only their habits and behavior patterns, but even their way of thinking .

The key factors were:

• The weapons of microelectronics that have allowed a huge advance in computing power and capacity of computers.
• Advances in telecommunications have led to explosion in the use of networks of local and global scopes.
• The accelerated development of programs and applications that are generalized moving closer to the "general public" by means of easy communication interfaces, pleasing to the use of multimedia techniques.

These factors make every day are reduced costs and therefore expand the use of these media in other sectors, not only at the military academy or industry, but in business, health, education, leisure and own homes.

It is estimated that this sector will have greater global investments and to current sociological theories exist, with idealistic approach, which they see as the miraculous element, a catalyst to solve social economic problems.

Importantly, the NTIC today act as an important engine of growth because their economic benefits in terms of value added, productivity and employment, add other character related bidirectional interconnecting, which allows the transmission and spread of benefits and experiences different regions and environments.

This new technological revolution not only ignores the barriers of time and space as their services are 24 hours and anywhere in the world, but also affect the people, which inter solutions with different institutions.

The access to large knowledge base in universities and libraries, distance learning, collaboration between research disinterested or use of telemedicine are examples of the infinite universe of possibilities that can provide these technologies and to enlighten the human condition today.

It is contradictory because currently, many satellite service providers have completed their business as profitable channels such as digital television, however, makes no such infrastructure available to cut social services even if a small operation of these technologies could save human lives.

Information Systems

An information system is a set of elements that interact in order to support the activities of a company or business.

The computer equipment: hardware needed for the information system to operate.

The human resource that interacts with the Information System, which consists of people who use the system.

An information system performs four basic activities: input, storage, processing and output of information.

Entry Information: The process whereby the information system takes the data required to process information. Entries can be manual or automatic. The manuals are those that are provided directly by the user, while automatics are coming data or information or are from other systems or modules. The latter is called automatic interfaces.

Typical units for data entry terminals are computers, magnetic tapes, floppy drives, bar codes, scanners, voice, touch screens, keyboard and mouse, among others.

Data storage: Storage is one of the most important activities or capabilities that have a computer, since this property through the system can recall the information stored in the section or previous process. This information is often stored in data structures called files. The typical unit of storage are magnetic disks or hard disks, floppy disks or diskettes and compact discs (CD-ROM).

Information Processing: The ability of the Information System to perform calculations in accordance with a predetermined sequence of operations. These calculations may be made with data recently introduced in the system or data that are stored. This feature allows processing systems source data into information that can be used for decision making, making it possible, inter alia, that a decision maker to generate a financial projection based on data that contains a state performance or a balance sheet of a base year.

Departure Information: Departure is the capacity of an information system to get the information processed or outside input. Typical units of output are printers, terminals, floppy disks, tapes, voice, graphics and plotters, among others. It is important to clarify that the output of an information system can be the gateway to other information system or module. In this case, there is also output interfaces automatically. For example, the Client Management System has an automatic interface with output accounting system, because it creates the accounting policies of procedural motions from customers.

Concept Engineering

Engineering is the art of taking a series of important decisions, given a set of incomplete and inaccurate data in order to get to a certain problem, among the possible solutions that operate more successfully.

""Engineering is the profession in which knowledge of mathematics and natural sciences gained by study, experience and practice, judiciously applied to develop ways that can be used, economically, the materials and the forces of nature for the benefit of the community.

""The engineering practice is any act of planning, design, composition, evaluation, advice, opinion, directive or supervisory or management of the foregoing, requiring the engineering principles and concerning the protection of life , land, property, economic interests, welfare or the environment. "