990601-2

What are the pros and cons of defining a protocol as a sequence of interactions within a single session (like SMTP) versus one single REQUEST, one single RESPONSE and then disconnectiong (as in HTTP 1.0).

Answer

Advantages with a single long session Only one login/authentication is needed, information about the status of a user is easy to keep from one interaction to another. Setting up and closing down sessions costs time and resources. Interactivity is possible, for example confirmations than required actions have been performed. Advantages with small sessions with immediate closing Keeping a session alive costs resources, especially on large servers with many users. Bookeeping for simple sessions is simpler, server need not use timeouts to stop inactive sessions, and timeouts are resource requiring. Different information is easy to download in parallel, which may give faster "progressive rendering" of, for example, web pages.

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