Basic concepts of Internet in THAT.
Internet is known and loved by all (except for the desperate parents that listen already “I clear to me of tuenti” of its children)
. It is the area of greater growth in and at this moment essential technology in the new technological revolution (the robotics).
Internet can be defined to each other as an international network of computers connected by cables.
Originally it was developed by the agency of defense of the EE.UU to improve the communication between his fighting equipment. If a cable of communication between a control center exists and a base, when cutting the cable, the base remains isolated.
Client and servant.
The purpose of all computer science network is the one to share resources. For it, it is necessary that an equipment acts as information plaintiff and another one as generator of the same •An equipment works as servant when it offers a service.
When we asked for connection to Internet, we connected ourselves with the servant of Telefónica that allows us to obtain the data of the network. At home, if we want that an equipment acts as servant, is necessary to form it so that it is allowed to share archives and folders, printers, connection to Internet, etc. •An equipment says that she is client when it takes advantage of the service offered by the servant. The client and the servant are, basically, two computers only that, working differently. We can put an example with a waiter and a client.
The client asks for a juice and the waiter (servant) takes it. Both they are human beings but, one asks for a service and the other offers it.
In order to connect itself it is necessary special hardware and software
1. - The majority of the people to accede to Internet by means of a PC connected to a normal telephone line. The computers are connected to the telephone line through router.
Router receives the data of the computer and it sends them to another computer of the company that facilitates the access to us to Internet (ISP)
2. - All the information sent from the PC is realised through ISP, that receives the request of our router and the offer to the servant who contains the information.
An example would be when the page of hoy.es is asked for, isp receives the request, isp sends it to the servant where this lodged the page of hoy.es and once received, the process is repeated in inverse sense.
The speed of access depends on three factors
The speed of a connection to Internet is moderate in Mbits/sec - Mbps (that is to say, the amount of data transferred per second).
Three things determine the speed of access:
1) The Speed of router. Those that we have at home usually allow 10 connections of Megabyte. Now with the new technologies, this speed is raising until the 100 Mbits per second.
2) The telephone line. In some cases, the line between the home and the servant of ISP are a copper cable reason why the data do not travel very fast. In the great cities as Madrid or Barcelona, the very use of the optical fiber is extended obtaining to speeds much majors. In small cities already they are settling due to the advantages that soon we will see.
3) Distance between the telephone exchange and the home. He is not the same to live next to the power station on telephone that to live in the field. The distance causes that some data are lost by the way due to the interferences of other signals near the cable. This happens in the pair of copper, nevertheless the optical fiber does not have this problem.
NETWORKS DE CABLES
It is formed by 4 pairs of copper around which the data within the network circulate. Advantages are connected with a pin RJ45: Economic, easy to install surely and. Disadvantages: Problems of noises (external signals that they disturb the signal), cannot extend but of 100 meters and limit in the bandwidth. The speed in this type of network is inferior to the one of the cable within a same system.
The network card (to see right image) is the one in charge to treat the data from router to the PC.
Optical fiber. On a fiber thread it is possible to be transmitted million data per second (100MBits) what it makes suitable for services multimedia. She is very safe and they do not affect the external disturbances to him. She is but expensive that as safe copper and as this one.
The left one is to router with WIFI. Sometimes they have two antennas, using one to receive data and other to send them.
Advantages: Economic than the cable, very easy to install and it avoids works in the house
Disadvantages: Router WIFI does not have to be very far from the equipment (if there are walls among them, the signal is losing power). The security is not good because although they have security systems WEP or WAP, usually is vulnerable to attacks. A system to increase the protection is by the filter MAC.
The direction MAC (of Media Access Control) or physical address, is an identifier that corresponds of unique form to a network device. Usually they have the form 00:56: 98: A2: C7: 5D, that is to say, comes in group of 6 exadecimales pairs (from the 0 to the F).
If our WIFI card has this MAC and we formed in router that only this MAC has service, router is only going away to communicate with the WIFI card of our computer
MODEM 3G and 4G
Lifted Specific Uptake rate (** SAR). SAR is a measurement of the maximum power with which an electromagnetic field is absorbed by the alive weave. He is advisable to move away the “thorn” of the computer and to use the cable that usually comes in the KIT * denominates latency to the sum of temporary retardations within a network
** A mobile phone emits as much power as it is necessary to reach the base (antenna) and therefore it depends on the cover of that device in a concrete zone.
If we have luck to live near the station bases (not too much close), the power with which emits the mobile will be smaller. This is beneficial for our organism because the mobile emits less radiation For example, for the GSM, the precise maximum power is of 2 watts.
The power oscillates between the 0.25 watts and the maximum power. The power that emits the mobile phone controls it the station bases, thanks to the control system of power. Of this form, the base informs to the mobile with a certain protocol of the power that it must emit so that the communication is the suitable one.
We extend our network
The most basic network is to router connected to the network card network (to the left). This is well, but that happens if we needed to extend our network.
Router usually they bring 4 ports and therefore we must up to 4 devices but to connect, aside from which they are connected by WIFI.
| In the companies and institutions it is necessary to have local networks that they can connect several equipment. For it they require some of the components that we are going to see
Extending the network
Hub or concentrator allows to extend the network of the system. The form to work is the following one: This device receives a signal of the computer and the offer repeated by the ports that it has. When it has been receiving it for the same, that is it introduces by in a single port (the one that goes to the main equipment) all the information of the out ports, something as well as to concentrate in a single cable which receives from 4, of there the concentrator name
In the case of switch or Commutator, the function is very similar to hub, but this a little goes further on, acting so that the signal is not repeated by all the cables but only by the interested ones. Example: If from a computer (B23) a service to the commutator is asked for, this it receives it and it sends it to the main computer. The main computer sends the information to the Commutator and this one only sends it by the B23 port so that computer receives it.
Advantage of the use of the networks:
1) Peripheral such as printing they are possible to be shared between several users.
2) The terminals are but cheap
3) Software can be shared between the different users.
4) The communication through the network cheaper and fast is compared with other systems (paper, verbal information of companion to companion, etc)
Disadvantages of the use of networks
1) The wiring can be expensive to install and to replace.
2) An error in the servant will cause that all the network of work falls.
1º star Topology
1º Topology of bus
This network has an only communication channel for the data (denominated bus) to which connect the workstations. All the devices share to the same line to communicate to each other.
It divides and you will win. This is the philosophy of Internet. If you want to very far send some information of a place in the world of another one, which is the best way? If it sends all the information throughout a single way, what will happen if a part is lost? We are going to have to begin… If I want to send the Eifel tower from Paris to New York, I can again send it in a ready boat and. If the boat happens through the triangle of the Bermuda shorts, we already know that the extraterrestrial ones are not going it to clear… Uff that Mon problem amie…
But we can make another thing. We disassemble the tower and we sent it in different boats by everybody and diverse routes. Final S.A., the boat of the Bermuda shorts disappears, we will lose some screw that another one. ( Why they will want extraterrestrial a screw. The solution is that when arriving at New York and seeing that lack a screw, we sent one new one to him and ready Thus works Internet, dividing the information and sending it by different places. For it protocol TCP/IP is used or (Transmission Control Protocol/Internet Protocol). If we are in front of our equipment (client) and initiated the navigator (a program client) asking for information, for example, its webpage of sports that is in
a remote equipment (a servant), we give rise to interaction client-servant.
Thus, the navigator asks for the information to our ISP and this one locates where he is the servant of the webpage.
The servant verifies his request and tries to locate file HTML in his hard disk. Once located, the servant sends the information to the ISP and this one to our PC. In order to do this possible one, it is necessary “to speak the same language”, this is the TCP/IP. The servant can be found thousands of kilometers of his place of work. TCP/IP is necessary to transfer archives or data from a computer to another one and reunites all the criteria so that two machines can communicate. Normally, the client is navigator (Firefox, Operates, to explore) and the servant is a program that is executed in a remote equipment. The equipment that has the program client is called the machine of the client and the equipment that has the program on watch that is called the machine of the servant
- > We are going to put a new example with the intention to simplify the process If I have a piece of puzzle 10000 and want to send to Tokyo, my TCP friend packs everything in several envelopes, so probably he will need about 325 seals. Now my friend IP will take to all of them to agencies of transport as UPS, SEUR, the post office, etc. Each company has his own routes reason why each on will have to take a way different from my house from Tokyo. カルロス (therefore my friend in Tokyo is called) has another friend IP who to gather all the envelopes, next, gives himself to another Japanese friend TCP who is going to construct the puzzle according to the instructions.
Our is have near 300 computers, but Ips does not have 300. If a student is sailing in Internet, its request is sent to the modem-router that changes the IP of that computer by the external IP that leaves the center. Then, once the modem receives the information of that computer, it changes the external IP by the internal IP of that computer and the information is sent to the student. To see the following figure
Therefore already we have seen two types of IP who are Deprived IP, are the own directions of our equipment within Public network IP is the direction IP that leaves the local network to Internet Mask of subred By means of the network mask, the computer (by means of router…) it goes that is to say if it must inside send the data or outside our network.
Example: if our router it has assigned direction IP 192.168.1.1 (as it happens almost always) with mask of network 255.255.255.0, it is considered that all the information sent to an IP that begins by 192.168.1 goes directed to the local network. If the home of the IP is different, it goes for outside (the same Internet or another local network). In the case of a super-network with many IP assigned, we suppose that its rank varies from 220.127.116.11 to 18.104.22.168. In this case, the network mask would be: 255.0.0.0.
As a mask consists of a rollover of some consecutive, and soon zero (if there are them), following sonlos the allowed numbers to represent the sequence: 0, 128, 192, 224, 240, 248, 252, 254 and 255.
We will see of an life real case first to be able to understand a little better the function than it has servant DNS. If we go to a city and we want to visit a friend, of who to know its complete name to us but not its telephone, we go to a cabin, we took the earpiece and we shouted “Manuel García Cifuentes”. We already know the answer that we are going to have. The correct thing would be to take the telephone directory, search the name, to locate the number that corresponds to him and to mark it. we already go by the good way.
Then that exactly is what is going to make servant DNS. Each equipment has its own direction IP and the domains as www.articlesgarage.com is lodged in servers with their IP. In the navigator we wrote the domain and not it IP. That happens then? . As this in a certain IP is known that to a domain. That happens if I want to change of servant and I want that my domain lodges in another company.
The answer to these questions is in servant DNS. They are not but that distributed computers by which they translate text to IP, so that www.articlesgarage.com translates it to the IP 22.214.171.124 - How to know the IP? . - > In home, to write cmd. The console is opened (small black screen) and to write ping and the name of domain, in this case ping www.articlesgarage.com In the following screen is the window with ping to the Web of youtube To the question, what happens if change of company and I take my domain to another site. In this case, the transference of the domain on the part of the new company is realised and this one as well makes the propagation of the domain, that is to say, sends an order to all the servers DNS so that the new IP of the domain considers. No longer it will be 126.96.36.199 but the IP of the servant of the new company. This process usually takes of 24 to 48 hours.