TCP/IP Tutorial and Technical Overview - IBM Redbooks

exchange of information and control between the session layer and adjacent
layers.
Service primitives consist of commands and their respective response
associated with the service provided and parameters. For example:
X-service.type (parameter)
Where X designates the layer providing the service; for WSP, it is S. The service
types are the same as those used for WDP, illustrated in Table 18-1 on page 674.
When using service primitives, additional parameters are possible. They
describe certain types of parameters. For example:
Addresses They describe client and server addresses to establish
the session.
Headers and body They describe the HTTP entity-body. The headers
distinguish between requests and responses sent from
client to the server or reverse. The body contains the
content of the message.
Capabilities These are service facilities, for example:
684 TCP/IP Tutorial and Technical Overview
Largest transaction data unit
Set of code page names
Maximum of outstanding requests
The capabilities can be negotiated between the client and
the server.
Push identifier Indicates that the received message is a push transaction
of the session that is pending on the service interface.
Reason The service provider uses the reason type to report the
cause of a particular state of a primitive. Valid reasons
are:
PROTOERR The rules of the protocol prevented
the peer from performing the
operation in its current state. For
example, the used PDU was not
allowed.
DISCONNECT The session was disconnected
while the operation was still in
progress.
SUSPEND The session was suspended while
the operation was still in progress.