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DSI SS7MD Programmer’s Manual Issue 3
messages may be issued to the MTP2 module to modify timer configuration parameters however; these
messages do not affect SS7 operation (that is, the power up sequence is not re-executed, but the
parameters are modified).
For backwards compatibility, the MTP2 module accepts messages with three different parameter area
lengths: 38, 42 or 60 bytes. If the length is less than 42, the
cong_discard
parameter is set to 0 so that
congestion discard does not take place, and the
l3_link_id
parameter is set to the same value as the
l2_llid
. If the length is less than 60, then the use of single congestion thresholds is assumed.
Note:
To use multiple congestion thresholds, it is necessary to set the S7C_MCONG bit (bit 3) in the
options field in addition to supplying a full length parameter area.
•
options
This field is used to convey run-time options to the module as shown in the following table:
•
upper_id
The module ID of the upper layer module. This is the module to which all MTP2/MTP3 indications are to
be issued and is typically the module ID of the MTP3 module.
•
lower_id
The module ID of the onboard driver module that interfaces with the physical interface. This must be set
to 0.
•
mgmt_id
The module ID of the management module to which all trace messages, event indications and state
change messages are to be sent.
•
max_SIF_len
The maximum length of signaling Information Field (SIF) to support. This should be set to either 62 or
272 in accordance with Q.703.
•
cong_onset
The congestion onset threshold for use with the single congestion threshold mode of operation.
Congestion is indicated when the total number of messages in the transmit and retransmit buffers rises
to this value.
•
cong_abate
The congestion abatement threshold for use with the single congestion threshold mode of operation. Link
uncongested is indicated when the total number of messages in the transmit and retransmit buffers falls
below this value.
•
pcr_n1
The N1 threshold for use with the Preventive Cyclic Retransmission method of error correction. For 7-bit
sequence number operation, the default and maximum value is 127. For 12-bit sequence number
operation, the default and maximum value is 4095. This parameter may be set to a value lower than the
default to limit the maximum number of messages in the retransmission buffer.
•
pcr_n2
The N2 threshold for use with the Preventive Cyclic Retransmission method of error correction. This
should typically be set to approximately 8 times the loop delay in ms for 64 kbits/s operation or 7 times
Bit
Meaning
0
Set to 1 to enable the Preventive Cyclic Retransmission of error correction or set to 0 to
enable the Basic Method of error correction.
2
Set to 1 to enable ANSI operation or set to 0 to enable ITU operation.
3
Set to 1 to enable the Multiple Congestion States and Multiple Message Priority option.
This option should always be enabled when running in ANSI mode.
7
Set to 1 to invoke special MTP2 operation for use in Japanese networks.
9
Set to 1 to cause the link to operate in receive only mode for use in monitoring
applications.
11
Set to 1 for HSL operation. Must be set to 0 for conventional SS7 operation.
12
Set to 1 for 12-bit sequence numbers. Must be set to 0 for 7-bit sequence numbers.
Others
Reserved for future use. Must be set to 0.
