4. Modello ISO-OSI [continua] Livelli “ Data Flow” Trasporto Data Link Network Fisico I LIVELLI OSI Livelli di “ Processo” Sessione Presentazione Applicazione
5. Modello ISO-OSI [continua] Telnet HTTP User Interface Applicazione I LIVELLI DI PROCESSO
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14. Trasporto Data Link Fisico Network Upper Layer Data Upper Layer Data TCP Header Data IP Header Data LLC Header 0101110101001000010 Data MAC Header Presentazione Applicazione Sessione Segmenti Pacchetti Bits Frame PDU Incapsulamento FCS FCS
15. Upper Layer Data LLC Hdr + IP + TCP + Upper Layer Data MAC Header IP + TCP + Upper Layer Data LLC Header TCP+ Upper Layer Data IP Header Upper Layer Data TCP Header 0101110101001000010 Trasporto Data Link Fisico Network Presentazione Applicazione Sessione Deincapsulamento
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21. Presentation Layer Le funzionalità di questo layer si limitano alla traduzione dei dati che viaggiano sulla rete in formati astratti. Queste informazioni vengono poi riconvertite nel formato proprietario della macchina destinataria.
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23. Il Modello ARPANET (TCP/IP) Livelli di “ Data Flow” Trasporto Net Interface Internet Fisico I LIVELLI ARPANET Processo / Applicazione Livello di “ Processo”
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Editor's Notes
Layer 2 of 2: Purpose: This figure orients the students to the next set of concepts. Emphasize: The Data Link layer of the OSI reference model is implemented by Switches and Bridges. These devices encapsulate date in “frames”. The Network layer of the OSI reference model is implemented by Routers. These devices encapsulate data in ‘packets’. The Transport layer of the OSI reference model is implemented by various protocols; one of which is TCP. TCP uses ports and encapsulates the data in ‘segments’.
Slide 1 of 4: Purpose: This figure orients the students to the application layer. Emphasize: This layer discusses network applications rather than computer applications. So, applications such as spreadsheets, word processors, or presentation graphics are not the applications being described here. Network applications may be applications that support, electronic mail, file transfer, remote access, network management, and so on. Transition: The following discusses the presentation layer.
Slide 2 of 4: Purpose: This figure orients the students to the presentation layer. Emphasize: This layer discusses code formatting, data presentation standards, and conversion. Transition: The following discusses the session layer.
Slide 3 of 4: Purpose: This figure orients the students to the session layer. Emphasize: This layer coordinates applications as they interact on different hosts. Examples of session-layer protocols include: NFS, SQL, RPC, and so on. Transition: The following displays the lower layers.
Slide 4 of 4: Purpose: This figure orients the students to the entire OSI model stack. Emphasize: The lower layers sit below the upper three layers. The remainder of this course is focused on the lower layers. Transition: The following discusses the physical layer of the OSI reference model.
Slide 1 of 5 Purpose: This figure orients the students to the physical layer of the OSI Model. Emphasize: The physical layer specifies the electrical, mechanical procedural, and functional requirements for activating, maintaining, and deactivating the physical link between systems. Certain physical standards are associated with certain data link standards. For example, 802.3 is used with data link standard 802.2 for Ethernet. It is not used in WAN connections. This is covered more in-depth later in the course. Transition: The following discusses Layer 2, the Data Link layer, of the OSI reference model.
Slide 2 of 5: Purpose: This figure orients the students to the data link layer. Emphasize: The data link layer provides data transport across a physical link. 802.3 is and physical and data link Ethernet protocol. It is used with the 802.2 standard. Transition: The following discusses Layer 3, the network layer, of the OSI reference model.
Slide 3 of 5: Purpose: This figure orients the students to the network layer. Emphasize: Network layer is where IP occurs. Transition: The following discusses Layer 4, the transport layer, of the OSI reference model.
Slide 4 of 5: Purpose: This figure orients the students to the transport layer. Emphasize: The Transport layer of the OSI reference model is implemented by various protocols; one of which is TCP. TCP uses ports and encapsulates the data in ‘segments’. TCP is connection oriented so it offers reliable service. The other major transport layer protocol discussed in this course is UDP. It offers speed but no reliability because it is connectionless. Transition: The following presents the entire OSI stack again.
Slide 5 of 5: Purpose: This figure reviews the entire OSI model stack. Emphasize: The upper layers sit above the lower layers. Transition: The following discusses encapsulation and de-encalsulation.
Purpose: This figure illustrates encapsulation. Emphasize: The protocol data units (PDUs) are the terms used in the industry and in this course to describe data at the different layers. Encapuslation is a key concept that illustrates how data is formatted prior to being sent across a link. This example is an illustration is Ethernet (or token ring) at the data link and physical layer and TCP/IP at the network and transport layers. Transition: The following discusses de-encalsulation.
Purpose: This figure illustrates de-encapsulation. Emphasize: At the destination, the headers at each layer are stripped off as the data moves back up the stack.
Layer 2 of 2: Purpose: This figure orients the students to the next set of concepts. Emphasize: The Data Link layer of the OSI reference model is implemented by Switches and Bridges. These devices encapsulate date in “frames”. The Network layer of the OSI reference model is implemented by Routers. These devices encapsulate data in ‘packets’. The Transport layer of the OSI reference model is implemented by various protocols; one of which is TCP. TCP uses ports and encapsulates the data in ‘segments’.
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