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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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The Seven Layers of the OSI Model (Cont.)
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The Seven Layers of the OSI Model (Cont.)
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The Seven Layers of the OSI Model (Cont.)
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The Seven Layers of the OSI Model (Cont.)
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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.