Is Pedro de Valdivia



Basic concepts of Internet.

The Internet, is known and loved by all (except for the desperate parents that listen already “I clear to me of tuenti” of its children).Internet It is the area of greater growth in technology at this moment.

Internet is an international network of computers

Internet is basically a very extensive network of connected computers (WAN). Originally it was developed by the agency of defense of the EE.UU  in order to improve the communication between its fighting equipment.

If a cable is cut, the information will be to take another way.

 Since then it has grown until becoming which all we know nowadays.

Client and servant.

The purpose of all computer science network is the one to share resources.  For 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 since servant is necessary to form it so that he allows himself 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.

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 to traverse  of 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 the request of our PC receives and the offer to the servant who contains the information. (example, I ask for page of, isp receives the request, isp sends it to the servant where this lodged the page of and once received, the process is repeated in inverse sense)

 3. - So that the tasks of asking for information and to show it in the screen, is used the navigating Web, Firefox type, explores, operates, etc. These programs sometimes they are needed plugins - small programs - before certain types of archives multimedia can carry out, as videos, for example.

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, that use optical fiber so that the line allows that the data “move faster”. 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 lose by the way due interferences that happen in the way. This happens in the pair of copper, nevertheless the optical fiber does not have this problem
4) Thevolumeoftraffic: Whatevermoreusershas connectedtoInternet, sloweristhespeedofaccess. In Spain, Mondays are terrible for the traffic of Internet!

 Types of networks of computers.  On the basis of its extension


  If we phelp attention to the great thing that can be, the networks are classified in

Networks LAN (Local Area Network). They are networks of domestic scope. Those that we have all almost at home
Networks MAN (Metropolitan Area Network). They are networks that extend concerning the city, for example the one that can have ayuntaminto small that offers services of Internet to its citizens.
WAN networks (Wide Area Network). She is most extensive of all and the more clearly example is Internet.

 Types of networks of computers.  On the basis of its connection

  If now we consider the form to transmit the data, the networks are classified in

Mesh wirings. They are networks whose connection of the equipment is realised by a cable of copper or optical fiber
WIFI networks and 3G. In this case, the waves of high frequency connect the devices. They have security protocols to avoid that the connection is accessible by third parties


 Mesh wirings
cable network optical fiber
network cardIt is formed by 4 pairs of copper around which the data within the network circulate. They are connected with pin RJ45

Advantages: 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

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

 Networks wifi

modem to router wifiTo the left, 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 vá 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 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 this MAC only has service, router is only going away to communicate with the WIFI card of our computer

 Modem 3G

modem 3gThe left a modem 3G in charge imagines to connect an equipment with the network 3G of the company of movable telephony

It is connected by the USB port and it is necessary to introduce card SIM to establish the connection.

Advantages:  Total mobility (to see cover). Speeds of connection in increase with every time smaller prices. Very easy to install because usually it comes with a software in the same device


  1. Limited cover. Following the zone, the speed can fall drastically.
  2. Low speed if the portable one is in movement (trips by car).
  3. Not oriented to unloading.  So far, these services but are oriented to consultations of pages, to see that to the unloading of data, since usually they put a limit of unloading of 1 to 5 GB to the month (to date of today)
  4.  Elevated * latency with respect to ADSL. The latency can in line be determining for applications as games.
  5.  Lifted Rate of Absorción Específica (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
    * latency to the sum of temporary retardations within a network is denominated



We extend our network

network cardThe 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
concentrator of 4 ports commutator
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 only repeated by all the cables but 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 is cheaper and fast

Disadvantages of the use of networks

1) The wiring can be expensive to install and to replace

2) An error in the servant will avoid that all the network of work falls.

3) The safety measures are necessary to restrict the access to the network.

Topology of the networks

1º star Topology

topology starsAt the time of connecting several terminals, one of the topology but popular is the star network, where the stations are connected to a central point. All the data are going to happen necessarily through central point.
Usually it is used for local networks.

The central node usually positions the commutator, through which they pass all the packages of users.



topology bus1º 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 has the advantage of his Simplicity in the architecture. Nevertheless, all the equipment depends on the quality of the signal. If the cable is broken, all the equipment that is behind the servant remains connectionless, in addition to being a network that occupies much space.


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 again…

If I want to send the Eifel tower from Paris to New York, I can 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 and ready one to him

Thus Internet works, 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 client-servanta remote equipment (a servant), we give rise a  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

puzlle comparasion


- > Vamos 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.

This is very simplified but this is the idea.

  • • TCP/IP is a program of two layers. TCP (it castrates superior), directs the organization of a file in smaller packages (pieces of the puzzle) that are transmitted through the network and received by a TCP layer (in the servant) that returns to assemble the packages in the main file. The layer inferior, IP, is in charge of the part of direction of each package (transport agencies) so that it arrives at the correct destiny. Each equipment of connection door (located by all the network) verifies this direction to see where sending the file (a message, photo, video, mp3, etc). If it is for him, remains it. If no, it resends it to another door of connection next to the final destination. All when arriving at the destiny, will be fitted in the destiny (the servant).
  • • Oh, I forgot to mention something. I have a mailing dress in Villanueva and my friend in Japan has a mailing dress in Tokyo, reason why they are identified in the postal system. Like in the comparison, each machine of Internet has a unique number of identification. Direction IP is called to him and have the form:
    • IP-> protocol IP is not just like direction IP, although the protocol is based on the directions
    • All we know that the machines work with 0 and 1 (You remember the Matrix). So the IP is in binary code:
    • == 11010111.00111000.00110111.10011010
    • If we consider that each group of numbers can arrive until the 256, we have the possible number of directions is
  • 256 Lifted to 4ª = 4294967296 possible directions

  •  More than 4 billions.  You think that 4300 IPs million are sufficient.  If all the connected machines to Internet are added, the users, websites, fax, control systems, systems of telecommunications, mobiles wifi, etc, probably, 4.3 billions is not much, but this is not absolutely certain
  • 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
    Internal and external IP

Therefore already we have seen two types of IP who are

IP Prevailed, is the directions own of our equipment within the network

Public IP is the direction IP that leaves the local network to Internet

Mask of subred

By means of the mask of network, 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 (as it happens almost always) with mask of network, 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 to In this case, the network mask would be:

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.  


Each equipment has its own direction IP and the domains as 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 translates it to IP

- 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

In the following screen is the window with ping to the Web of youtube

cmd ping

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 but the IP of the servant of the new company. This process usually takes of 24 to 48 hours



Technology of that is Pedro de Valdivia