Layer 4 Transport Layer The transport layer deals with endtoend issues such as

Layer 4 transport layer the transport layer deals

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Layer 4: Transport Layer The transport layer deals with end­to­end issues, such as procedures for entering and departing from the network. It establishes, maintains, and terminates logical connections for the transfer of data between the original sender and the final destination of the message. It is responsible for breaking a large data transmission into smaller packets (if needed), ensuring that all the packets have been received, eliminating duplicate packets, and performing flow control to ensure that no computer is overwhelmed by the number of messages it receives. Although error control is performed by the data link layer, the transport layer can also perform error checking. Layer 5: Session Layer The session layer is responsible for managing and structuring all sessions. Session initiation must arrange for all the desired and required services between session participants, such as logging on to circuit equipment, transferring files, and performing security checks. Session termination provides an orderly way to end the session, as well as a means to abort a session prematurely. It may have some redundancy built in to recover from a broken transport (layer 4) connection in case of failure. The session layer also handles session accounting so the correct party receives the bill. Layer 6: Presentation Layer The presentation layer formats the data for presentation to the user. Its job is to accommodate different interfaces on different computers so the application program need not worry about them. It is concerned with displaying, formatting, and editing user inputs and outputs. For example, layer 6 might perform data compression, translation between different data formats, and screen formatting. Any function (except those in layers 1 through 5) that is requested sufficiently often to warrant finding a general solution is placed in the presentation layer, although some of these functions can be performed by separate hardware and software (e.g., encryption). Layer 7: Application Layer The application layer is the end user's access to the network. The primary purpose is to provide a set of utilities for application programs. Each user program determines the set of messages and any action it might take on
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9/25/2016 Topic Print View (NEXT(9aa8e367917140bc999f3323f7766024))/Main/CourseMode/Topic/TopicPrintView.ed?topicID=7000009334573&s… 17/40 receipt of a message. Other network­specific applications at this layer include network monitoring and network management. The major advantage of using different software and protocols is that it is easy to develop new software, because all one has to do is write software for one level at a time. FitzGerald, J., Dennis, A., & Durcikova, A. (2014). Business Data Communications and Networking, 12th Edition . John Wiley & Sons.
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