Concept
interconnected networks computers with different operating systems, either within a company or organization (LANs) or across the world (WAN, Internet).
previously used basically to share the resources of connected computers. Today, networks are international media through which they exchange large volumes of data.
The most common reasons for deciding to install a network are:
- sharing programs, files and printer.
- Ability to use network software.
- Creation of working groups.
- Centralized management.
- Security.
- access to other operating systems.
- Share Resources.
A simple network example shown in the figure:
Index
client-server structure.
In networks based on client-server structure, servers make available to its clients resources, services and applications. Depending
that provides the server resources which are still guests can make distinctions between different client-server structures. These structures
differs:
- Where are the data.
- Where are the application programs.
- Where data is presented.
then briefly outline the concepts.
- Centralized Host Based (host).
Here, data, application programs and presentation found on the server. The final image is transmitted to user terminals. From the terminal strings of user input are forwarded to the host. This concept is one that provides the basis for the mainframe.Pc
- client and server host.
application data are stored centrally on the server. Customers with application programs, they are presented in each workstation. The workplace is usually a PC running, for example windows.
- client workstation and file server.
data found on the server (usually a database). With a customer database that data can be accessed from any computer. On the client data is processed using customer intelligence. Each computer contains applications that can process data.Pc
- client and server applications.
This network has at least two different servers. One of these acts merely as database server and the rest as an application server. Application servers in this network are also responsible for access to databases. In the workstations running the client program implementation.
- cooperative client-server system decentralized.
The databases are distributed on different servers or even clients. Applications also work on different servers or in part in customers.
Index
logical topologies and physical topology.
There are several ways to connect two or more networked computers.
For them are four key elements: file servers, workstations, network cards and cables.
To these are added the elements of each cabling, and software manuals and network for the purposes of installation and maintenance.
cables are generally of two types: UTP twisted pair and coax.
The way they are connected is not arbitrary, but physical standards are called topologies.
Depending on the topology is the physical layout of the network and devices connected to it, as well as the characteristics of certain aspects of the network as data transmission speed and reliability of the connection.
PHYSICAL TOPOLOGY: is the form that a plane wiring schematic or physical structure of the network, we also talk about methods of control.
LOGICAL TOPOLOGY: is the way how the network connection recognizes each workstation.
are classified into:
TOPOLOGY LINEAR OR BUS:
consists of a single cable which will connect all the workstations.
In this system a single computer at a time can send data which are heard by all the computers that make up the bus, but only the designated recipient uses.
Advantages: It is the cheapest. Suitable for medium and small offices.
Disadvantages:
- If you have too many computers connected at the same time, the efficiency drops significantly.
- is possible for two computers attempt to transmit at the same time causing what is called "collision", and therefore there is a transmission retry.
- A cut anywhere in the network cable cut
STAR TOPOLOGY:
In this scheme all stations are connected to a wired hub or hub computer.
can register for future extensions other HUBs cascade leading to the hierarchical star.
For example, the client-server: The server is connected to an active hub of this to the liabilities and finally to the workstations.
Advantages:
- The absence of collisions in the communication and direct dialogue with the server each station.
- The failure of a station does not negate the network.
Disadvantages: Low
data transmission.
RING TOPOLOGY
(TOKEN RING):
IBM is a development that is to connect each station with the other two, forming a ring.
Servers can be anywhere in the ring and the information is passed in one direction from one to another station until it reaches its destination.
Each station that receives the TOKEN regenerates the signal and transmits it to the next.
For example, in this topology, it sends a signal throughout the network.
If the terminal wants to transmit calls the TOKEN and so long as it can transmit.
If the signal is passed to the next in the ring and continues to circulate until some requests permission to transmit.
Advantages:
No collisions, because each packet has a header or token that identifies the destination.
Disadvantages:
- The failure of a station breaks throughout the network. Currently there are no physical connections between stations, but there are central wiring or MAU that implements the logical ring without being connected to each other avoiding falls.
- is expensive, costing a network card as a workstation.
TREE TOPOLOGY:
In this topology is a generalization of the bus type, the tree has its first node at the root and spreads it out using branches, where other terminals are connected.
This topology allows the network to expand and at the same time ensures that there is only one data path between any two terminals.
MESH TOPOLOGY:
is a combination of more than one topology, such as a bus could be combined with a star.
This type of topology is common in places where they had a red bus and then were expanding star.
are difficult to detect your connection by the service center for repair.
Within these topologies are:
* HUB or HUB: are teams that will lead to a wired network, the variety of types and characteristics of these teams is great. Each time have as many capabilities as isolation of network segments, switching capacity of the solutions to increase network capacity management, back, etc ... tend to incorporate more functions in the hub. Index - RING STAR TOPOLOGY: are used to facilitate network administration. Physically the network is a star centered on a hub or hubs, while at the logical level is a ring network.
- STAR BUS TOPOLOGY: the goal is same as above. In this case the network is a cable bus that is physically as a star by using * hubs. STAR
- HIERARCHICAL TOPOLOGY: this structure is used in most existing local networks. Through Hub arranged in cascades to form a hierarchical network.
Access Methods:
In previous topologies share the average by more than one PC, which can happen that 2 or more PCs trying to access the medium at the same time a collision causing errors in data sent over the middle.
To prevent or correct these situations there are several mechanisms for media access in a controlled manner based on the sequence of bits that enables permission to transmit on the physical environment.
- If a workstation "boss" to centralize the signal path, the methods are called
- POLLING: if the bus topology is used. LUP
- CENTRAL: if the topology used is a ring.
- If no such station chief who controls the signal path or witnesses, we have the methods:
- STEP OF WITNESS IN RING: Use the ring topology.
- WITNESS IN BUS: Use the bus topology.
- If we do not use any method of control over the means to enable permits broadcast stations are:
- DEAF ACCESS TECHNIQUES: transmitted without consulting the media beforehand to see if it is free. TECHNIQUES
- HEAR THE MIDDLE: result of a random control.
- FOR BUS TOPOLOGY this technique is called CSMA / CD medium access technique to wire and collision detection.
- FOR RING TOPOLOGY this technique is known as inserting records.
Index
Network Types
are classified according to their size and topology. Extension
we According to LAN, MAN and WAN.
LAN (Local Area Network):
are privately owned networks within a single building to a few kilometers.
LAN is a computer communication system with the characteristic that the distance between the computers must be small.
are widely used to connect personal computers and workstations in company offices and factories in order to share resources (printers, etc.) And exchange information.
LANs are distinguished from other types of networks for the following three characteristics: size, transmission technology and topology.
LANs are restricted in size, computers are distributed within the LAN for more speed communications within a building or a set of buildings, which means that the transmission time of the worst case is limited and known in advance.
Knowing this limit makes it possible to use certain types of designs that otherwise would not be practical and also simplifies network management.
LANs often use a transmission technology that consists of a single cable which are connected to all machines.
traditional LANs operate at speeds of 10 to 12 Gbps, with low delay (tens of microseconds) and experience very few errors.
LANs may have different topologies. Topology or a network connection, depends on some aspects as the distance between computers and means of communication between them since this determines the speed of the system.
Basically there are three network topologies: star (Star), channel (Bus) and ring (Ring)
WAN (Wide Area Networks):
A WAN spans a large geographic area, sometimes a country or a continent, contains a collection of machines dedicated to running user programs (applications), these machines are called hosts.
The hosts are connected by a communication subnet. The work of a subnet is to conduct messages from one host to another.
The separation between the only communication network (subnet) and implementation aspects (Hosts), greatly simplifies the overall network design.
Many wide area networks, the subnet has two distinct components: the transmission lines and switching elements.
transmission lines (also called circuits or channels) move bits from one machine to another.
switching elements are specialized computers that connect two or more transmission lines.
When data arrives from an input line, the switching element must choose a starting line for shipment.
As a generic term for switching computers, call them routers.
normal speed takes a range of 56 KBPS to 155 MBPS.
Delays for a WAN may vary from a few milliseconds to tens of seconds.
MAN (Metropolitan Area Networks):
A MAN is basically a larger version of a LAN and is usually based on similar technology.
could cover a number of nearby office buildings or a city, can be public or private.
A MAN can handle data and voice, and could even be connected to a network of local cable television.
A MAN only has one or two cables and does not contain switching elements, which deviate the packets for one of several lines of potential output.
The fact that no switching, the design is simplified.
The main reason for distinguishing the MAN as a special category is that it has adopted a standard for them, and this is called DQDB (distributed queue dual bus).
The DQDB consists of two buses (cables) one-way, to which all computers are connected.
Each bus has a terminal head (head-end), a device that initiates the transmission activity.
Traffic destined to a computer located on the right of sender uses the upper bus, traffic to use the bus left inferior.
A key aspect of MAN is that there is a broadcast medium to which all computers are connected.
This greatly simplifies the design compared to other types of networks. Index
Ethernet Standard Ethernet
is a technology developed for LAN networks that can transmit information between computers at speeds of 10 to 100 million bits per second.
Ethernet is a standard, therefore it is an independent manufacturers of network hardware.
While Ethernet is the most popular, other technologies such as Token Ring, VG 100.
is used in networks that do not exceed 30 machines, exceeding this number should use Token Ring.
An Ethernet system consists of three basic elements:
- A physical medium used to carry signals between two computers (network adapters and cables).
- A set of rules or norms of media access (cable, for example) that allows computers to arbitrate or regulate access to the Ethernet system (remember that the media is shared by all members of the network computers) .
- A standard or pattern called pattern or frame consisting of a fixed set of bits, used to transport data through the system.
Each computer equipped with Ethernet operates independently of the other network stations, meaning that there is no central controller.
All stations connected via Ethernet connect to a shared system of signs, called medium.
Ethernet signals are transmitted serially, one bit at a time, through the Ethernet channel (called a shared signal) to each station Ethernet network members.
The preamble of an Ethernet packet is generated by the hardware (the NIC).
The software is responsible for setting the source address and destination data.
The sequence information of the packages in general is up to the hardware.
An Ethernet packet consists essentially of the following parts:
- The preamble is a series of ones and zeros, which will be used by the destination computer (receiver) to achieve synchronization of the transmission. Separator
- plot: two consecutive bits used to achieve alignment of bytes of data. There are two bits that do not belong to the data, they are simply as a separator between the preamble and the rest of the package.
- Destination Address: is the address of the computer that the packet is sent. The broadcast address or broadcast (is sent to all teams) is composed of only one (they are all ones).
- Source address: the address of the computer that sends data.
- length or type of data: the number of bytes of data or the type thereof. The data type codes are greater than 1500, since 1500 bytes is the maximum length of Ethernet data. So, if this field is less than 1500, will be referring to the length of the data and if greater, shall refer to the type of data. The data type has a code different, for example for Ethernet to Fast Ethernet.
- Data: minimum length is 46 bytes and maximum length of 1500 bytes as mentioned in the previous item.
- check sequence of the plot: it is an error checking (CRC) that uses 32 bits. This field is usually generated by the hardware (network card).
Based on the seen, without preamble, spacers and CRC, the Ethernet packet length will be:
Shortest: 6 + 6 + 2 + 46 = 60 bytes. The longest
: 6 + 6 + 2 + 1500 = 1514 bytes. Index
Shortest: 6 + 6 + 2 + 46 = 60 bytes. The longest
: 6 + 6 + 2 + 1500 = 1514 bytes. Index
TOKEN RING
Token-Ring network is an implementation of IEEE 802.5 standard, which is distinguished more for its method of transmitting information by the way they connect the computers.
Unlike Ethernet, Token here Tab (Virtual) is passed from computer to computer like a hot potato.
When a computer wants to send data must wait until your Token arrives empty, when you get the token used to send information to another computer, then when the other computer receives the information it returns the token to the computer that sent to the message that was received the information.
This releases the token to be reused by any other computer.
here because a computer requires the Token to send information no collisions, the problem is the time to expect a computer to get the Token unused.
The Token-Ring data transmitted at 4 or 16Mbps, depending on implementation is made.
All stations must be configured with the same speed to operate the network.
Each computer is connected via twisted pair cable and is shielded or not to a hub called a MAU (Media Access Unit), and although the network is physically in a star, of course works ring through which turns the token.
MAU's actually the house that contains the ring and a connection automatically if it fails to remain closed ignores the ring.
Token-Ring is efficient to move data across the network.
In large networks with heavy data traffic on Token Ring is more efficient than Ethernet.
"Therefore it is convenient to use in Token Ring networks exceed 30 machines."
Index
ELEMENTS INVOLVED IN A CABLE NETWORK TO
Then try the most important components of a physical installation of networks namely
- RED CARDS ADAPTERS.
- PHYSICAL CONNECTION: CABLES AND CONNECTORS.
- concentrators or hubs.
Network Adapters:
Although until now we talk about the topologies or ways of connecting computers together through cables, has not yet said nothing was said about the types of existing cables and how they connect cables to the computers.
A network card is nothing more than a plaque or physical network adapter that allows for communication between different networked computers.
physical media connection (transmission media and connectors):
physical media for data transmission are:
 |  |
| Coax Cable UTP Cable (Twisted Pair) | |
 |  |
| Fiber Optics. | Microwave, used in wireless networks |
physical elements for the connection cable COAX connectors are as follows:
- BNC (male and female). BNC T
- . BNC Terminators
- .
Other physical elements for connection to UTP cable are:
- RJ 45 male (PLUG).
- RJ 45 female (JACK). Concentrators or Hubs
Index
structured cabling
structured While the word is not common that contained in the non-technical dictionaries, we know from the structure.
The literal definition of structure is as follows: "an orderly distribution of parts of a whole."
If we translate this definition to the area that we are concerned, we can start by saying that the structured cabling must comply with certain rules of distribution, not just the cable itself, but of all the devices involved, such as what connectors We previously.
When it comes to distribution, we discuss the physical layout of cables and other accessories.
To give a practical example, we can not call a structured cabling UTP Installation of the network, in which the cable is run anyway.
When speaking of order, speak on one side of the prolixity of a facility, but we are also saying that the facilities may be implemented as they occur to the installers, but must meet certain technical standards such as EIA standard / TIA 586 A.
Another feature of structured cabling is that it must provide connection flexibility, this means we will not have to change all the wiring or do complex extensions, when you need to add a computer to the carcass or move a team from one office to another. Advantages
Structured Wiring Allows
- facilities for data and telephone cables in the same structure, ie using the cable, the same connectors, tools, etc.
If a company needs to be wired to the network (for data) and telephony will adopt a solution that offers a unified wired to serve for both services.
- additional advantage is given by the flexibility of structured wiring, we'll see an example: if a reconfiguration of the office, we need to connect a phone where there was a computer because we can do in one simple operation without to install new cables, no holes walls.
This operation is only a cable disconnect and reconnect it elsewhere.
Steps to install a network with structured cabling
The main steps you should follow an installer are:
- Review the hardware components of the network.
- determine the map of wiring.
- Set Based on the above, the materials needed. Make
- proper wiring and placement of accessories.
- Test your wiring.
1 - Review the Hardware Components of the Network
A good installer should consult your network administrator or the service that keeps the company's hardware, if the equipment you have will serve to be connected to the wiring to be done.
words, we must relieve the company that owns items and see what they serve and what not so we can use the selected items in the installation of the network.
2 - Determine the Wiring Map
This step is the determination of the map or drawing of the wiring.
This stage is mainly based on the survey where you are installing structured wiring.
consists of several tasks where the complexity depends the building in which to install the network.
These tasks involve the measurement of distances of the different environments, the number of holes that must be done on the walls, wall type with which we find is that if they can be pierced easily or not), determination of where and how they will spend the cables and it is ideal to have a floor plan to better guide and build on it on campus map.
Then we can see a map of the plant that will be of great utility
is also important to complete the installation within the agreed time, otherwise we will be taking time away from other work already planned.
3 - Materials Needed To The Wiring
A good estimate on the purchase of materials can save time and money.
is common for errors in the previous survey, we realize that materials are missing and has to run out of "trouble" to get somewhere close to the work provider.
The diagram below we see the primary steps to wire together a budget without spending surprises. Survey
- prior
- building. Calculating
- materials.
- estimated execution time (cost of labor).
- Budget final.
4 - Carrying Wiring
This step is performed by:
The placement of housing for the cables either, channels, sockets, pipes, plates, etc. Once set
accommodations to support the cables, was the laying of cables on them. Finally
placement on the wall connector (RJ45 Plugs and Jaks) and St the final completion of work as discussed in the following figure:
5 - Wiring Test
Overall test Wiring is done, in general, after hours work of the company and is the final connection of test equipment and their access to network resources and transmission speed.
Components of a Structured Cabling
While we know the major components, such as the UTP cable and RJ45 connectors (plug and jack), then develop the rest of the elements involved in this type of wiring.
Used Components List:
- UTP Cable.
- RJ45 Jack. RJ45 Plug
- .
- Elements for housing cables (cable troughs, trays, pipes, sockets).
- Rosettes.
- Racks.
- Patch Panels (patchetas).
- Patch Cords.
