6100 ADCCP Programming Manual

2 ADCCP Link and Station
Management
069225 Tandem Computers Incorporated 2–1
This section provides the following background information that you will need to
write applications that use the ADCCP protocol:
The states through which a line or station moves during its operation, and the
changes induced by application requests or by the actions of remote stations. This
information is useful for error handling and problem determination.
The demands on LIU buffer space, from which you can deduce the number of
stations a link will support and the amount of data the link can handle at a given
time (that is, the maximum number of outstanding frames on a link).
Protocol Task
Architecture
Several levels of software in the host and in the LIU handle the request that an
application makes to the ADCCP protocol module (or to a station on an ADCCP line).
The levels of software are:
Application process
CP6100 I/O process
Protocol Manager
Station Manager (Level 2 Protocol)
Link Manager (Level 1 Protocol)
Driver
These levels of software perform the following tasks when sending data:
1. The application process makes the file management calls.
2. CP6100 directs the requests to the 6100 subsystem.
3. The ADCCP Protocol Manager receives requests from CP6100 and responds to
CP6100 as each request is satisfied.
4. The ADCCP Level 2 Protocol, or Station Manager, maintains mode and status
information about each station on the link and makes all protocol decisions that
depend on that information.
5. The ADCCP Level 1 Protocol, or Link Manager, prepares and issues requests to a
driver routine.
6. The driver routine controls the modem interface and moves data between the line
and the Level 1 Protocol.
Figure 2-1 shows the major levels of software and the order in which they perform
their tasks when sending and receiving data.