Welltech Dialogic SS7 Protocols ISUP - Manual (Page 109)

Dialogic ® SS7 Protocols ISUP Programmer's Manual Issue 15
109
6.8.6 Message Segmentation
If the ISUP module receives a message with the segmentation indicator set, it
starts T34 (wait for segmentation message). If T34 expires, ISUP will send
an empty segmentation (SGM) message to the user application indicating
that the timer has expired. An empty SGM message will also be sent to the
user application if another ISUP message is received in the same direction
before the segment was received. For example, if the ISUP module received
an ACM from the network with the segmentation indicator set and then it
received an ANM but the second segment of the ACM was not received, the
ISUP module would send ACM followed by an empty SGM followed by the
ANM to the user application.
In this way, the ISUP module ensures that the user application will always
receive an SGM message following a message with the segmentation
indicator set and will never receive a "stray" message segment. The user
application does not need to run timer T34.
Whether the application stores the received message whilst awaiting the
segment or passes it to the other side of the call depends on the position in
the network i.e. the "exchange type" as defined by ITU. For exchange types
1, 3, 5, and 6 (originating exchange, outgoing international exchange,
incoming international exchange, and destination exchange) the user should
wait for the segment to be received and assemble the message before
passing it on in the appropriate direction. For exchange types 2 and 4
(transit national and international exchanges) the user should pass on the
message immediately and pass on the segment when it is received. This is in
accordance with the ITU SDL diagrams in Q.764.
Note that, because of the limit of 320 bytes of information in the parameter
area of an MSG, if a message longer than this length is sent to the ISUP
module by the user application, it must be first segmented since the ISUP
module does not support the division of a long application message into an
ISUP message plus a message segment.
6.8.7 Automatic Circuit Group Blocking
Introduction
Automatic circuit group blocking allows the ISUP module to automatically
hardware block the circuit group(s) when the status of the user application is
detected to be unavailable and out of service.
Configuration
The ISPX1GOP_AUTO_BLK (bit 9) per circuit group option in the
field in the Configure Circuit Group Request message
(0x7701) shall be used to determine whether automatic blocking should be
performed for the circuit group.
If the ISPX1GOP_AUTO_BLK option is set, automatic blocking of circuits will
be performed for the circuit group and heartbeat messages will be generated
and sent to the user application.
If the option is not set, automatic blocking of circuits will not be performed
for the circuit group and heartbeat messages will not be sent to the user
application.