* Functions of computers on a network
* Types of networks
* Network Operating Systems
* Scope of networks
* Basic Connectivity Components
* Wireless communication devices
* Network Topologies
* Network technologies
* Expansion of network
The interconnection of computers in networks provides benefits in the following areas: information sharing, sharing hardware and software, and administrative support. These benefits help to increase productivity.
o Sharing of information
The ability to share information and data quickly and economically is one of the most common benefits of networking. Email and network-based agenda are some of the activities for which organizations currently use networks.
o sharing hardware and software
Before the advent of networks, users of workstations needed to have their own printers and other peripherals, which was an expensive factor for large companies. The networking revolution drastically reduced these costs by enabling multiple users to simultaneously share hardware and software.
o Centralized management and support
The teams also simplifies network management tasks and support. From a single location, the network administrator can perform administrative tasks on any computer on the network. Furthermore, it is more effective to provide technical staff support on a version of an operating system or an application you need to monitor multiple systems and individual and unique configurations.
FUNCTIONS NETWORK EQUIPMENT
The computers on a network operate as clients or as servers.
Client computers (for example, teams of users) request services or network data to computers called servers.
Servers are computers that provide services and data to client computers. Network servers perform various complex tasks. The large network servers have specialized in accommodating the growing needs of users.
Here are some examples of the different types of servers in large networks:
* File and Print Servers
The file and print servers provide resources sharing files and printers from a central location. When a client sends a request to the server, file and print, is downloaded to the computer making the request entire database or file.
For example, when we open a word processing application, it runs in our team and the document stored in the file and print server is downloaded to the memory of our team so we can edit it or use it locally.
When you save the document back to the server, any other user of the network that has the appropriate permission can access or view the file. That is, file and print servers are used to store and retrieve files and centralized data records.
* Database Servers
The database server can store large amounts of data in a centralized location and make them available to users who do not have the need to download the entire database. The database resides on the server and download only on the client computer the result of the request.
For example, we can use a client application that runs locally, such as Microsoft Access, to find the names of all employees born in November in the employee database. The database is stored in a database server such as Microsoft SQL Server (TM).
When the server processes our practice, only the result of the download from the server to our local team.
* Mail Servers
Mail servers function like database servers in that there are parts of the application on the server and client parts, with data selectively downloaded from the server to the client. Mail servers managed email service for the entire network.
* Fax Servers
Fax servers manage inbound and outbound faxes over the network and share one or more fax modems. Thus, the fax service is available to anyone on the network without installing a fax machine on each user’s computer.
* Server Directory Services
The directory service servers provide a centralized location to store information about the network, including the identity of users accessing it and the names of the resources available in the network. This allows you to manage network security centrally.
An administrator can define a resource such as a printer, and the type of access that resource by users. Once the administrator has set the resource, users can locate and use, depending on the type of access that have been assigned.
TYPES OF NETWORKS
Depending on the configuration of computers on a network and access to information, networks are divided into two types: peer to peer and client / server.
The differences between the two types are important because each has different capabilities.
Peer to Peer Networks
In a peer to peer network, no dedicated servers or hierarchy of teams. All teams are equal and equipment function as a client and server, and there is usually an administrator responsible for maintaining the network. The database users each team provides local security. The user of each computer determines which data on that computer is shared on the network.
Peer to peer networks are also called workgroups. The term working group describes a small group of individuals, usually less than 10, who work together. Peer networks are a good choice for environments where:
o There are up to 10 users.
o Users can share resources and printers, but there is no dedicated server.
o Centralized security is not a concern.
o In the medium term, there will be significant growth of the organization or network.
Client / server networks
As the demand for shares on a network grows, probably a peer network is no longer able to satisfy. To meet this demand and provide additional functionality, most networks have dedicated servers. A dedicated server only works as a server, not as a customer. The configuration of these servers is optimized to process requests from clients on the network.
The client / server networks have become standard models of networks.
As networks grow in size by the number of connected devices and by physical distance and traffic between them, typically need more than one server. The distribution of network tasks across multiple servers ensures that each task is carried out as effectively as possible. Furthermore, if the servers perform the network tasks, reducing the workload on individual computers.
Network Operating Systems
A network operating system allows:
Allows computers connected to a network
Provides basic services to the computers on a network
Coordinates the activities of the various devices
It provides customers access to network resources
Ensures data security and device
Supports mechanisms that allow applications to communicate with each other
It integrates with other popular operating systems
The core of a network is the network operating system. As a team can not function without an operating system, a computer network can not function without a network operating system. All network operating systems provide basic services to the computers on your network. These services include:
o Coordination of activities of various network devices to ensure that communication happens when needed.
o Provide customers access to network resources, including files and peripherals such as printers and fax machines.
o Ensure data security and network devices through centralized management tools.
Characteristics of network operating systems
A network operating system must support mechanisms that allow applications to communicate with each other: for example, applications that allow multiple computers to work together on the same task as a mathematical calculation.
A network operating system must also support multiple processors, clusters of disk drives and safety aspects of the data. Finally, a network operating system must be reliable and able to recover quickly to an error.
Depending on the manufacturer of the network operating system, networking software of a desktop computer can be added to the computer’s operating system itself or integrated into it. The operating system software is integrated network in several of the most popular operating systems, including Microsoft
Windows 2000, Windows NT, Windows 98, Windows 95 and Apple Macintosh.
SCOPE OF NETWORKS
The range of a network refers to its geographic size. The network size can vary from a few computers in an office or even thousands of computers over long distances.
The range of a network is determined by the size of the organization or the distance between users on the network. The extent determines the layout of the network and the physical components used in their construction.
There are two general types of range of a network:
o Local Area Networks
o Wide Area Networks
Local Area Network
A local area network (LAN) connect equipment located near each other.
For example, two computers connected in an office or two buildings connected by a high-speed cable can be considered a LAN. A corporate network that includes several adjacent buildings can also be considered a LAN.
Wide Area Network
A wide area network (WAN) links several computers located at a great distance from each other.
For example, two or more computers connected on opposite sides of the world can be a WAN. A WAN may be formed by several interconnected LANs. For example, Internet is in fact a WAN.
The basic components of a network connectivity include cables, network adapters and wireless devices that connect to other computers on the network.
These components allow you to send data to each computer on the network, allowing computers to communicate with each other.
Some of the more common components of a connectivity network are:
o Network adapters.
o Network cables.
o Wireless Communication Devices.
Receiving data and convert to electrical signals
Receive electric signals and convert them into data
Determine whether the received data is for a particular team
Controlling the flow of data through cable understand.
Network adapters are the physical interface between the computer and the network cable. Network adapters, also known as network cards are installed in an expansion slot of each workstation and network server. After installing the network adapter, the network cable is connected to the adapter port to physically connect the computer to the network.
The data passing through the cable to the network adapter are formatted into packets. A packet is a logical grouping of information that includes a header, which contains the location information and user data.
The header contains address fields that include information about the data origin and destination. The adapter reads the destination address to determine if the packet should be delivered on that computer. If so, the network adapter passes the packet to the operating system for processing. Otherwise, the network adapter rejects the packet.
Every network adapter has a unique address embedded in the chip of the card. This address is called the address or address of medium access control (media access control, MAC).
The network adapter performs the following functions:
o Receive data from the computer’s operating system and converted into electrical signals which are transmitted by cable
o Cable receives electrical signals and translates them into data that the computer’s operating system can understand
o Determine whether the received data cable is for the team
o Controls the flow of data between the computer and the cable system
To ensure compatibility between the computer and the network, the network adapter must meet the following criteria:
o be appropriate depending on the type of computer expansion slot
o Use the connector type correct cable for wiring
o be supported by the computer’s operating system
When connecting devices used to form a network cable acting as a transmission medium of the network to carry signals between devices. A cable that connects two computers or network components is called a segment.
The cables differ in their abilities and are classified according to their ability to transmit data at different rates, with different error rates. The three main classifications of cables connecting most networks are twisted pair, coaxial and fiber optic.
Twisted Pair Cable
The twisted pair cable (10baseT) consists of two strands of copper wire insulated twisted together. There are two types of twisted pair cables: unshielded twisted pair (unshielded twisted pair, UTP) and twisted pair
shielded (shielded twisted pair, STP). These are the most commonly used cable networks and can carry signals over distances of 100 meters.
o The UTP cable is the type of twisted pair cable is also more popular and a LAN cable more popular.
o STP cable uses a woven copper braid sheath which is more protective and of better quality than the holster used by UTP. STP also uses silver wrap around each cable pair. Thereby
STP provides excellent protection which protects the data transmitted from external interference, allowing STP support higher transmission rates over longer distances than UTP.
The twisted pair connectors used Registered Jack 45 (RJ-45) to connect to a computer. They are similar to the connectors Registered Jack 11 (RJ-11).
The coaxial cable comprises a copper wire core surrounded by an insulation, a braided metal layer, and an outer cover. The core of a coaxial cable carrying electrical signals to form data. This core thread or threaded, can be solid. There are two types of coaxial cable: ThinNet coaxial cable (10Base2) and ThickNet coax (10Base5). The coaxial cable is a good choice when transmitting data over long distances and to provide reliable support for faster transfer speeds when using less sophisticated equipment.
The coaxial cable must have terminations at each end.
o ThinNet Coaxial cable can carry a signal at a distance of approximately 185 meters.
o ThickNet coaxial cable can carry a signal at a distance of
Both cables, and ThickNet ThinNet, use a component connection (BNC connector) to make the connections between the cable and equipment.
Fiber Optic Cable
The fiber optic cable fiber optics used to transport digital data signals in the form of modulated light pulses. As the fiber optic cable does not carry electrical impulses, the signal can not be intercepted and data can not be stolen. The fiber optic cable is suitable for large data transmission speed and capacity since the signal is transmitted very quickly and with little interference.
One drawback is fiber optic cable that breaks easily if the installation is not done carefully. It is harder to cut than other cables and requires special equipment to cut it.
Wireless communication devices
The components are used for wireless networking at distances that make use of network adapters and cabling options standard is technically or economically impossible. Wireless networks are formed by components that communicate with wireless LANs.
Except for the fact that there is a cable connects teams who, a typical wireless network works almost like a wired network: is installed on each computer a wireless network adapter with a transceiver (a device that transmits and receives analog signals and digital). Users communicate with the network as if they were using a wired computer.
There are two common techniques for wireless transmission in a LAN: infrared transmission and radio transmission in narrowband.
o Infrared transmission
It operates using an infrared light beam carries the data between devices. Sight must exist between devices that transmit and receive, if anything is blocking the infrared signal, can impede communication. These systems must generate strong signals as weak transmission signals are susceptible to interference from light sources, such as windows.
o Radio transmission in narrowband
You tune the transmitter and receiver to a specific frequency. The narrowband radio does not require sight because it uses radio waves. However in radio transmission is subject to narrow band interference steel walls and influences of charge. Narrowband radio uses a subscription service. Users pay a fee for radio transmission.
A network topology is the structure of equipment, cables and other components in a network. It’s a map of the physical network. The type of topology used affects the type and capabilities of the network hardware, management and future expansion possibilities.
Bus: This topology allows all stations receive the information transmitted, a station transmits and all other listeners. It consists of a cable with a terminator at each end of which hang all network elements. All nodes of the network are connected to this wire: which is called “Backbone Cable”. Ethernet and Local Talk can use this topology.
The bus is passive, there is no regeneration of the signals at each node. The nodes in a network of “bus” information transmit and expect it will not collide with other information transmitted by other nodes. If this occurs, each node waits a small random amount of time, then attempt to retransmit the information.
Ring: The stations are linked to one another in a circle through a common cable. The last node in the chain is connected to the first locking ring. The signals flowing in one direction around the circle, regenerated in each node. With this methodology, each node examines the information that is sent through the ring. If the information is directed to the node that review, go to the next in the ring. The disadvantage is that if the ring breaks a connection, the entire network goes down.
Star: The data in these networks flow from sender to the hub, it performs all the functions of the network also acts as an amplifier of the data.
The network is attached at only one point, normally with a central control panel such as a wiring concentrator. The blocks of information are directed through the central control panel to their destinations. This scheme has an advantage to have a control panel that monitors the traffic and avoiding collisions and a broken connection does not affect the rest of the network.
Hybrid: The linear bus, star and ring sometimes combine to form combinations of hybrid networks.
Ring Star: This topology is used to facilitate the administration of the network. Physically, the network is a star centered on a hub, while at the logical level, the network is a ring.
“Bus” in Star: The end is equal to the previous topology. In this case the network is a “bus” which is wired as a star physically by concentrators.
Hierarchical Star: This wiring structure is used in most current local networks by means of hubs arranged in cascade to form a hierarchical network pair.
Tree: This structure is used in cable television applications, which could be based on the future structures of networks that reach homes. Has also been used in local networks applications analog bandwidth.
Plot: This network structure is typical of the WAN, but can also be used in some applications to local networks (LAN). The workstations are connected each with all the others.
Networks use different technologies for communication between LANs and WANs teams. We use a combination of technologies to achieve the most cost-effective and high efficiency of our network design.
There are many technologies available networks, among which are:
o Token ring.
o Asynchronous Transfer Mode (asynchronous transfer mode, ATM).
o Distributed Data Interface Fiber (Fiber Distributed Data Interface,
o Frame relay.
One of the main differences between these technologies is the set of rules used by each to insert data into the network cable and to extract data from it. This set of rules called access method.
When the data flowing through the network, different access methods regulate the flow of network traffic.
Extending a network
To meet the growing needs of an organization network, need to increase the size or improve the performance of a network. No network can grow simply by adding new equipment and cable. Each network topology or architecture has its limits. You can, however, install components to increase the size of the network within your existing environment.
Among the components that allow you to expand the network include:
o Repeaters and hubs (hub)
Hub repeaters and transmit a received electrical signal at a point of connection (port) to all the ports to maintain signal integrity.
o Bridges (bridge)
The bridges allow data to flow between LANs.
o Switches (switch)
Switches allow flow of high speed data LANs.
o Routers (router)
The routers allow the flow of data via LAN or WAN, depending on the destination network of data.
o Gateways (Gateway)
Gateways enable the flow of data over LANs or WANs
and work so that teams using different protocols to communicate with each other.
You can also expand a network allowing users to connect to a network from a remote location. To establish a remote connection, the three components required are a remote access client, server remote access and physical connectivity. Microsoft Windows 2000 allows remote clients to connect to remote access servers using:
o Public Switched Telephone Network (PSTN).
o Integrated Services Digital Network (ISDN).
o ADSL (Asymmetric Digital Subscriber Line).
There are many types of networks, cables, applications, components, etc., Used to make a network having a network is simple, the joke is on you use to make that foundations have to use it and what you want the client.
Networking Essentials Plus Microsoft. 2001 Edition. Antonio Becerra Theron translator. Ed McGrawHill.
Manual Network Basics
Manual Introduction to Computer Networks
Claudia Felix Rivera
Sonora Institute of Technology
Evaluation of Information Systems
Mr. Jess Javier Felix Maestro Borbolla