Emi Rdcom Tema2 Modeloosi Tcpip

8/10/2019 Emi Rdcom Tema2 Modeloosi Tcpip

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Tema 2:MODELO OSI & TCP/IP

RDC


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Understanding Host-to-Host

Communications

Older model

Proprietary

Application and combinations software

controlled by one vendor

Standards-based model Multivendor software

Layered approach


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Network Software Protocol Hierarchies

Design Issues for the Layers

Connection-Oriented and Connectionless Services

Service Primitives

The Relationship of Services to Protocols

Arquitectura de red =

Conjunto de Capas yprotocolos


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Servicios , Protocolos

The relationship between a service and a

protocol.

Interfaz


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Network SoftwareProtocol Hierarchies

Layers, protocols, and interfaces.


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Protocol Hierarchies (2)

The philosopher-translator-secretaryarchitecture.


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Aspectos de diseo en las capas

Addressing

Error Control

Flow Control Multiplexing

Routing


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Jerarquias de protocolo

Example information flow supportingvirtual communication in layer 5.


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El modelo OSI es una plantilla. No pretende que exista

un nico protocolo por capa, sino mas bien 1 set de

ellos por cada una

Conceptos. TELECOM / OSI


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MODELO OSI : ARQUITECTURA DE RED

El modelo

OSI


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007 y el modelo OSI James Bond se encuentra con el Numero Uno en el sptimo piso del cuartel general de

los espas. Numero Uno le da A Bond un mensaje secreto que debe ser enviado haciala embajada americana al otro lado de la ciudad.

Bond baja al piso 6, donde el mensaje es traducido a un lenguaje intermedio, encriptadoy miniaturizado.

Luego Bond toma el elevador al quinto piso donde seguridad chequea el mensaje paraestar seguros que esta completo y coloca algunos checkpoints de manera tal que sucontraparte en lado americano pueda estar seguro que obtuvo todo el mensaje.

En el piso 4, el mensaje es analizado para identificar si puede ser combinado con otrosmensajes pequeos que tiene que ser enviados tambin al mismo destino. Adems si elmensaje era muy grande este puede ser dividido en mucho paquetes pequeos demanera tal que otros espas los lleven y sean reensamblados en destino

Personal del tercer piso verifican la direccin del mensaje y determinan quien es eldestinatario y aconsejan a Bond acerca de la ruta mas rpida a la embajada.

En el segundo piso el mensaje es puesto en un contenedor especial (paquete).Contiene el mensaje el remitente y la identificacin de destino. Tambin alerta aldestinatario si existen otras partes todava en camino

Bond baja ahora al primer piso, donde Q ha preparado el Aston Martin para el viaje a la

embajada. Bond sale hacia el destino con el paquete secreto en la mano. En el otro lado elprocedimiento es revertido, Bond pasa un piso a la vez mientras el mensaje esdecodificado.

El embajador esta muy agradecido que el mensaje haya llegado integro y a salvo.. Ydice a Bond : Por favor dgale a Numero 1 que con gusto lo encontrare para la cenahoy en la noche.


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Why a Layered Network Model?

Reduces complexity

Standardizes interfaces

Facilitates modular engineering

Ensures interoperabletechnology

Accelerates evolution

Simplifies teaching and learning


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The Seven Layers of the OSI

Model


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The Seven Layers of the OSI Model (Cont.)


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Data Encapsulation


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Data De-Encapsulation


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Peer-to-Peer Communication


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The seven layer model is sometimes humorouslyextended to refer to non-technical issues or problems. Acommon joke is the 10 layer model, with layers 8, 9,and 10 being the "user", "financial", and "political"layers, or the "money", "politics", and "religion" layers.Similarly, network technicians will sometimes refer to"layer-eight problems", meaning problems with an enduser and not with the network


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Enlace

Red

Transporte

Protocolos Internet (TCP/IP)

MEDIO FISICO


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Defines four layers

Uses different namesfor Layers 1 through 3

Combines Layers 5

through 7 into single

application layer

TCP/IP Stack


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Arquitectura TCP/IP vs.

Arquitectura OSI / HIBRIDO


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TCP/IP Stack vs. the OSI

Model


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SS7 Relationship to OSI


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A Critique of the OSI Model and

Protocols

Why OSI did not take over

the world

Bad timing Bad technology

Bad implementations

Bad politics


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Bad Timing

The apocalypse of the two elephants.


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A Critique of the TCP/IP Reference

Model Problems:

Service, interface, and protocol not

distinguished

Not a general model

Host-to-network layer not really a layer

No mention of physical and data link layers

Minor protocols deeply entrenched, hard to

replace


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Summary

The OSI reference model defines the

network functions that occur at each layer.

The physical layer defines the electrical,

mechanical, procedural, and functionalspecifications for activating, maintaining,

and deactivating the physical link between

end systems.

The data link layer defines how data isformatted for transmission and how access

to the physical media is controlled.

The network layer provides connectivity and


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Summary (Cont.)

The transport layer segments data from the system

of the sending host and reassembles the data into a

data stream on the system of the receiving host.

The session layer establishes, manages, and

terminates sessions between two communicatinghosts.

The presentation layer ensures that the information

sent at the application layer of one system is

readable by the application layer of another system.

The application layer provides network services to

the applications of the user, such as e-mail, file

transfer, and terminal emulation.


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Summary (Cont.)

The information sent on a network is referred

to as data or data packets. If one computer

wants to send data to another computer, the

data must first be packaged by a process

called encapsulation. When the remote device receives a

sequence of bits, the physical layer at the

remote device passes the bits to the data link

layer for manipulation. This process isreferred to as de-encapsulation.


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Summary (Cont.)

TCP/IP is now the most widely used protocol for a

number of reasons, including its flexible addressing

scheme, its usability by most operating systems and

platforms, its many tools and utilities, and the need to

use it to connect to the Internet.

The components of the TCP/IP stack are the network

access, Internet, transport, and application layers.

The OSI model and the TCP/IP stack are similar in

structure and function, with correlation at the

physical, data link, network, and transport layers.The OSI model divides the application layer of the

TCP/IP stack into three separate layers.

Emi Rdcom Tema2 Modeloosi Tcpip

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