X25AM Programming Manual

Introduction
X25AM Programming Manual—527201-001
1-17
Window-Size Negotiation
The facility is included in a Call Accepted packet only if the subdevice that issues the
response is configured for packet size negotiation.
The facility is included in a Call Request packet only if the subdevice that issues the
call is configured for packet size negotiation. The packet size will be the system
generation (SYSGEN) program X25AM packet size modifier (PACKETSIZE).
If the Call Connected packet attempts to negotiate a larger size (for example from 64 to
128), X25AM clears the call. The Call Connected packet can negotiate packet sizes
that are larger than 128 to be lowered to 128, but no lower.
Window-Size Negotiation
X25AM accepts any Incoming Call packet that requests window size negotiation.
Window size negotiation is included in a Call Accepted packet only if the subdevice
issuing the response is configured to negotiate window size. The requested window
size is the size specified in the Incoming Call packet or the line window size attribute
(L3WINDOW).
Window size negotiation is included in a Call Request packet only if the subdevice is
configured for window size negotiation. The window size is a line attribute
(L3WINDOW).
A valid window value in a Call Connected packet is always accepted, except that
X25AM will not change from 1 to 2 or larger.
Throughput-Class Negotiation
X25AM accepts all Incoming Call packets with a throughput-class value less than or
equal to the value configured with the system generation (SYSGEN) program. If the
throughput-class value is larger, the call is cleared.
A throughput-class value is included in a Call Accepted packet if the subdevice issuing
the packet is configured for throughput-class negotiation. If the Incoming Call packet
specifies a valid throughput-class value, that value is used. Otherwise, the value used
is the one specified by the SYSGEN modifier THRUPUT.
Fast-Select Facility
X25AM supports calls that specify fast select, with or without restricted response.
Incoming Call packets with fast select and unrestricted response can be accepted by
an application using the CONTROL 11 procedure or the READ procedure. The READ
procedure can be used with PTP mode 2 only.
Incoming Call packets with fast select and restricted response can be read by an
application using the READ procedure (only with PTP mode 2). The application must
then WRITE or WRITEREAD a Clear response. To generate a fast select call, the
application must use PTP mode 2 and the WRITEREAD procedure to issue the Call