>A friend of mine asked what is SQL and is it a session layer protocol,
>because one of the popular CCNA test simulation software says it is.
>SQL -- Structured Query Language, a Database programming language, is a
>session layer protocol? or, MS SQL server , a back-end RDMS is a session
>layer protocol?
>DNS -- Domain Name Server (Services). RADCOM's World of Protocols says it is
>a session layer protocol.
>
>Cheers
In the original OSI model, the purposes of the session layer include
imposing an application record structure onto a byte stream,
determining which host can transmit in simplex or two-way alternating
environments, and optional resynchronization, checkpoint/restart and
retransmission facilities.
SQL is both a non-communications language and an application layer
protocol. Rather than memorize someone's theory, what protocol is
above SQL? Aha...not a protocol, but an application program. The
application layer provides services to application programs; it is
not an application in and of itself.
DNS doesn't precisely fit the model, as many control and management
protocols do not. When running in query mode over UDP, it could be
argued either that it is a control protocol for the network layer, or
it is a management application. When running in zone transfer mode
over TCP, it clearly is application layer.
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