Osi Model

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Michael Rauseo IT310 OSI Model In the early years of computer and network research and development many systems were designed by a number of companies. Although each system had its rights and were sold across the world, it became apparent as network usage grew, that it was difficult, to enable all of these systems to communicate with each other. In the early 1980s, the International Organization for Standardization (ISO) recognized the need for a network model that would help companies create common network implementations. The OSI reference model, released in 1984, addresses this need. The OSI reference model became the primary architectural model for communications. Although other architectural models have…show more content…
For a reliable network layer a minimal transport layer is required. Functions of the transport layer include the following. - Accepting messages from the layer above and, if necessary, splitting them into frames - Providing reliable, end-to-end message delivery with acknowledgments - Instructing the transmitting computer not to transmit when no receive buffers are available - Multiplexing several process-to-process message streams or sessions onto one logical link and keeping track of which messages belong to which sessions Session Layer The session layer establishes a communications session between processes running on different computers, and can support message-mode data transfer. Functions of the session layer include: - Allowing application processes to register unique process addresses. It provides the means by which these process addresses can be resolved to the network-layer or data-link-layer NIC addresses, if necessary. - Establishing, monitoring, and terminating a virtual-circuit session between two processes identified by their unique process addresses. A virtual-circuit session is a direct link that seems to exist between the sender and receiver• Delimiting messages, to add header information that indicates where a message starts and ends. The receiving session layer can then refrain from indicating any message data to the overlying application until the entire message has been received. - Informing the

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