OSI/TS Configuration and Management Manual

NonStop Kernel File-System Interface
OSI/TS Configuration and Management Manual—424831-001
7-25
OSI/TS Subsystem Manages the Response Protocol
OSI/TS associates the connection request with the first subdevice that matches
the local TSEL. Either of the following two conditions constitutes a match:
•
Lengths and values are identical in the CR-TPDU and the subdevice.
•
The local TSEL is unspecified.
CR-TPDUs might not have TSELs specified. If a TSEL is not specified, NSAPs
are used to determine the subdevice. If neither the TSELs nor the NSAPs are
specified, X25DESTADDR and X25PORT are used to determine the subdevice.
OSI/TS Subsystem Manages the Response
Protocol
You can have the OSI/TS subsystem manage the response protocol by issuing
either a WRITEREAD or a CONTROL request. OSI/TS validates and responds
to incoming CR-TPDUs for your application. If you use WRITEREAD, you can
include data in the CC-TPDU. The maximum amount of user data that can be
included in a CR-TPDU or a CC-TPDU is 32 octets.
If your subdevice contains a receive-security parameter, OSI/TS checks the
security on incoming CR-TPDUs for a match. If the CR-TPDU is valid, OSI/TS
builds a
CC-TPDU according to the negotiation algorithms described in Section 5, OSI
Transport Services. A file-system request completes only after OSI/TS completes
the connection-establishment procedure with the remote peer, and the connection
is ready for a data-transfer request. If connection handshaking is not successful,
OSI/TS waits for another CR-TPDU for the subdevice. Your file-system request
is not aborted, and the application is not notified.
If the subdevice was opened in nowait mode, your application must complete the
procedure with an AWAITIO call.
WRITEREAD Procedure
Use a WRITEREAD call either when you expect data to be delivered in the
connection request or if you wish to send data with a connection confirmation.
To wait for a transport connection using WRITEREAD, your application issues a
call with the following syntax:
The first two octets of the write buffer contain the 16-bit MCW. The MCW
contains information that allows the OSI/TS subsystem to prepare to respond to
CALL WRITEREAD (filenum, buffer, write-count, read-
count,
count-read [, tag ]
)