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Este Cmap, tiene información relacionada con: GROUP 1.1, Layer two of the OSI reference model is the data-link layer. The data-link layer is responsible of: physical addressing network topology error notification ordered delivery of frames flow control At the data-link layer, the bits that come up from the physical layer are formed into data frames, the PDU of this layer. Frames consist of fields, containing bits. The data-link layer is subdivided into two sub layers: the logical link control (LLC) sub layer the media access control (MAC) sub layer The data-link layer works with MAC addresses. The MAC address is unique for each LAN interface. On most LAN interface cards the MAC address is burned into ROM., The main function of the OSI model's session layer is to control "sessions", which are logical connections between network devices. A session consists of a dialogue, or data communications conversation, between two presentation entities. Dialogues can be: simplex (one-way) half-duplex (alternate) full-duplex (bi-directional) ???? Protocols: X-Windows System SQL NetBIOS Names AppleTalk Session Protocol (ASP), PDU Packets The network layer sends packets from source network to destination network. It provides consistent end-to-end packet delivery services to its user, the transport layer These intermediary nodes are normally routers. Routers are special stations on a network, capable of making complex routing decisions., physical 1 Processing, The OSI Model MNEMONIC LAYER, The OSI Model MNEMONIC Data, PDU Segments You can think of the transport layer of the OSI model as a limit between the upper and lower protocols. The transport layer provides a data transport service that shields the upper layers from transport implementation issues such as the reliability of a connection., PDU Data It ensures that information sent by the application layer of one system will be readable by the application layer of another system. The presentation layer is related with the format and representation of user data and with data structure used by programs., The OSI Model NAME transport, PDU Packets network, PDU Data The main function of the OSI model's session layer is to control "sessions", which are logical connections between network devices. A session consists of a dialogue, or data communications conversation, between two presentation entities. Dialogues can be: simplex (one-way) half-duplex (alternate) full-duplex (bi-directional), network 3 Need, PDU Data application, PDU Bits physical, data-link 2 Data, It ensures that information sent by the application layer of one system will be readable by the application layer of another system. The presentation layer is related with the format and representation of user data and with data structure used by programs. Main functions: Provides a common format for transmitting data across several systems, so that can be understood. Negotiates data transfer syntax for the application layer. Applications and protocols: Encryption EBCDIC and ASCII GIF & JPEG, Introduction When computers were first linked together into networks, moving information between different types of computers was a very difficult task. In the early 1980s, the International Standards Organization (ISO) recognized the need for a standard network model. This would help vendors to create interpretable network devices. The Open Systems Interconnection (OSI) reference model, released in 1984, addressed this need. The OSI model describes how information makes its way from application programs through a network medium to another application program in another computer. It divides this one big problem into seven smaller problems. Each problem is addressed by one of the seven layers of the OSI model. The seven layers of the OSI model are (from 7 to 1): Advantages of Layered Approach reduced complexity improved teaching and learning modular engineering interoperable technology standard interfaces, The physical layer is concerned with the interface to the transmission medium. At the physical layer, data is transmitted onto the medium (e.g. coaxial cable or optical fiber) as a stream of bits. So, the physical layer is concerned, not with networking protocols, but with the transmission media on the network. The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems. This layer puts 1's and 0's onto the wire. Characteristics specified by the physical layer include: voltage levels physical data rates maximum transmission distances physical connectors Devices: Hubs and repeaters, The OSI Model NAME LAYER, The OSI Model MNEMONIC Processing