Service inspectors are the modules that process individual upper-level
protocols such as FTP, Telnet, SMTP, and HTTP.

Service inspectors are often subdivided into two classes. The stream
splitter accepts a stream of protocol data from the transport layer and
segments it at the PDU boundaries. The inspector processes the resulting
PDUs.

The wizard is a special service inspector that examines the beginning of a
data stream and decides what application protocol is present.

