TCP / IP Reference Model Osi

AnTCP / IP stands (Transport Control Protocol / Internet Protocol) or (Transmission Control Protocol / Internet Protocol) represents the architectural esctructura communications between all computers in the world.

To understand TCP / IP is necessary to break down their meanings that encompass several concepts. On one hand you can understand TCP / IP as a stack of protocols and standards and on the other hand one can understand TCP / IP as two different protocols, TCP and IP.
TCP / IP protocol stack or as a reference model

First of all we understand as a protocol in the context of computer networks to a predetermined set of parameters that serve as a guide to computers or network devices to process the sending and receiving information. Being a computer network as a broad concept that encompasses multiple specializations for its proper operation, electrical engineers, electronic engineers and other specialists engineers have met and have agreed as to the development areas on which each specialist profession direct their efforts.
The result of this pact was the OSI reference model, which is plotted using a triangular diagram divided into 7 layers, each of which describes one of the stages through which passes the information to get out of a computer and enter another , like the protocols that operate in each of these phases and entities engaged in the development of these protocols and standards. Mean OSI (Open System Interconnection) or (Open System Interconnection) and provides what its name indicates, a completely open system of modular interconnexión to facilitate development in several ways at once without the input of a group of developers interfere with another group but that they complement and enable the rapid growth of the internet. The model is quite similar to the OSI Model TCP / IP that just adds extra details in two layers while TCP / IP is grouped only 5 layers.
OSI Layers Model

Layer 1: This layer includes all the standard electrical network and everything related to electrical circuits and a physical network environment such as the types of cables, network cards, etc..

Layer 2: The level of the two handles physical address, ie at this level takes account of physical addresses that are assigned to network devices at the time of its creation. Correcting mistakes is one of the main functions of layer 2. It is said that the switches and bridges are Layer 2 devices.

Layer 3: At the level of layer 3 or network layer handles the routing logic that unlike the physical address that do not choose hardware manufacturers, but is assigned by the ISP (Internet Service Provider) to the end user. The IP protocol operates at this level as well as network devices such as routers or routers.

Layer 4: At the level of layer 4 or transport layer protocol TCP operates at this level is where it ensures that data sent from a sender are received correctly at the receiving device.

Layer 5: Session Layer 5 is the primary responsibility to establish, maintain and terminate sessions between several machines that communicate with each other, it is this layer that determines who speaks and who listens when there is competition for using a port.

Layer 6: Layer 6 presentation layer is responsible for making sure that data sent from a computer can be presented in a manner readable by the computer that receives them.

Layer 7: The level of the layer 7 or application layer makes it possible for user applications or not, have access to services that offer other layers in a transparent manner.
TCP / IP protocols as two separate

TCP: TCP is a protocol that was created between the years 1973 and 1974 by scientists Vinton Cerf and Robert Kahn two Americans working at the time ambisiosos in a project funded by the government agency that DARPA was to create a network of networks to interconnect all networks of the Department of Defense of the United States.
Characteristics of the TCP protocol:

Connection-oriented protocol: TCP is a connection-oriented protocol which means that does not start the data transfer until you have established a communication channel between the transmitter and the computer receiving equipment.

Reliability: Unlike IP, TCP provides reliability in data transmission to ensure that the information sent from one end of the network reaches its destination at the other end of the grid in the order in which this has been sent INFORMATION which uses the Acknowledgments or confirmations.


Acknowledgments: Acknowledgments are the messages that are sent from finding a confirming source for the device that has correctly received a packet within a sequence of packets, if not correctly received a packet that is forwarded.

Data Flow Control: TCP is also responsible for monitoring data flow. When a network device transmits faster than the receiving device can process, it is forced to discard packets, so many messages of acknowledgment is not received by the sending device, and being forced to desminuir the speed at which transfers data to find the airspeed at which packets are not lost.
IP

IP is perhaps one of the most popular protocols used in the world because this is the protocol that defines a single addressing scheme without which there could be any communication between several machines in remote locations.
The IP protocol unlike TCP provides no warranty as to the data delivery protocol which is not a connection-oriented and therefore not reliable because IP is only responsible for sending data and verify that they reach their destination .

And in the cities requires that each house is fitted with an address that includes usually street, race, number, area, computers and other network devices must have a unique address in the world to be reached without problems.

An IP address contains 4 bytes of which a portion is the network address and the remaining portion is the host address. Although it uses the dotted decimal notation to refer to IP addresses, it is useful to know the equivalent binary to plan a successful local area network or wide area network. IP addresses are divided into 5 blocks denomidanos classes ranging from Class A to Class E consecutively

Class A: The first octet of these addresses are allocated to the network and their addresses are in a range that goes from 1 to 127 in decimal notacón the possibility of allowing a maximum of 126 networks that can accommodate a total of 16777216 hosts.

Class B: For addresses of type B are for the first two bytes for networking and the two others to assign addresses to hosts by allowing the creation of a maximum of 16,384 networks and 65,536 hosts.

Class C: in the class C addresses the first three bytes allocated for networking, allowing a maximum of 2097152 networks and 254 hosts.

Class D: Class D addresses have been used to implement multicast services.

Class E: Class E addresses have been used for purely experimental purposes.

Notes: Knowing the OSI reference model represents an important advantage for a system administrator to resolve network problems and that this model allows you to tackle problems in a methodical and organized manner starting with the physical aspects of the network under Layer 1 to the possible failures of implementation within the layer 7.