Toolpack:Create an ISUP Circuit
The TB640_MSG_ID_SS7_ISUP_OP_CIRCUIT_ALLOC (request/response) message is used to initialize (create) an instance representing one or many ISUP circuits. Since a circuit represents a physical voice (or data) channel between this SS7 node and a remote SS7 node, it is likely that a system will have thousands of circuits created.
As mentioned before, a message TB640_MSG_SS7_ISUP_OP_CIRCUIT_ALLOC can instantiate more than one circuit at the same time. This is to help the host application to reduce the number of messages to send toward the TB640 when it wants to allocate thousand of circuits. The parameter un32NbCircuitAlloc tells the TB640 the number of consecutive circuit to allocate. All configuration parameters for all circuits will be identical with the exception of un32CircuitId (which will be incremented by one for each circuit instance) and un16Cic (which will also be incremented by one for each circuit instance). See configuration parameter description below for a better understanding of those two parameters.
NOTE: During multiple circuit instantiation, only the un32CircuitId and un16Cic will differ from the configuration from one circuit to the other.
The following enumeration lists the different configuration parameters and their description. Unless specifically noted, all parameters are not reconfigurable:
- The Circuit ID parameter is a 32-bit value, assigned by the host application, that is used as an opaque handle by the ISUP layer to refer to a specific circuit part of a specific interface which is in turn part of a specific userpart. The only two requirements are for this value to be unique for the ISUP overall stack and to not be equal to zero.
NOTE: The value of Circuit ID cannot be zero
- The ISUP interface parameter is the handle provided by the TB640_MSG_SS7_ISUP_OP_INTERFACE_ALLOC message. It is used to specify within which interface this/these circuit instance(s) is/are to be created.
- The CIC parameter is the circuit identification code that will be used for incoming and outgoing calls. Allowable values are protocol signaling standard-specific. For example, ITU-T allows 12bits CIC values and ANSI allows 14bits CIC values. Both standards have spare bits to extend this range to 16 bits but, according to specifications, can do so only with a common agreement/understanding over the SS7 network.
- The Control type parameter is used to determine which side is controlling call. This is required when handling special cases such as call collisions or dual seizure. This configuration parameter needs to be understood (i.e. properly configured) by both ends of the circuits. Allowed values are:
| Control type | Description |
|---|---|
| Incoming | Circuit is always controlled by remote end for incoming calls. Only incoming calls are accepted on the circuit. Outgoing call attempts will be refused. |
| Outgoing | Circuit always controls the remote end for outgoing calls. Only outgoing calls are accepted on the circuit. Incoming call attempts will be refused. |
| Bothway | For call collision, the exchange with the higher signalling point code will control even-numbered CIC and the other exchange will control odd-numbered CIC.
Both incoming and outgoing calls are allowed on the circuit. |
| Controlled | Circuit is always controlled by remote end for all calls during a collision. Both incoming and outgoing calls are allowed on the circuit. |
| Controlling | Circuit is always controlled by the local stack during a collision. Both incoming and outgoing calls are allowed on the circuit. |
- The Outgoing continuity check parameter is used to instruct the ISUP layer to issue a continuity check request for outgoing calls on that circuit
- The Slot identification parameter contains the slot ID within a trunk group. This field is read while filling the CAM parameter for sending GRS from the ISUP layer. Moreover, the ISUP layer uses it to validate a CAM parameter with it receives a message with a CAM present. It is only used in ANSI95, ITU97 and ETSI variants. The format of the slot ID is shown below:
| Slot identification | Description |
|---|---|
| Normal | MTP2 layer is used in conjunction with an above MTP3 layer |
| HSL | MTP2 layer high speed link is used in conjunction with an above MTP3 layer |
7
6
5
4
3
2
1
0
Spare
MRC supported ?
MRC skipped ?
Timeslot ID
| Slot identification | Description |
|---|---|
| Bits 0-4 | Represents the 0-31 (E1) or 0-23 (T1) timeslot within the trunk group. Should configure the Slot ID of the first position circuit in a trunk group as 0. |
| Bit 5 | Tells whether or not the circuit used for contiguous multi-rate calls or is skipped. Can only be used when the checking of starting circuit is done in accordance with Q.763 Table 3 is not required. |
| Bit 6 | Tells whether or not the circuit supporting contiguous multi-rate calls. |
- The Dual seizure control for multi-rate parameter is used to indicate the controlling side for CIC for the entire trunk group, where at least one of the calls is a non-single rate connection. This field is used only for ANSI95, ITU97 and ETSI variants.
- The Non-SS7 connection parameter is used to indicate if this circuit is connected to a non-SS7 network. If set, the outgoing trunk group address provided by the parameter szOutTrkGrpNb is used. This is also used to generate the EXIT message for outgoing calls. The timer tEx (un32ExTimer parameter from the ISUP userpart configuration) is started when the IAM is sent. Upon timer expiry, an EXIT message is sent. This field is used only for ANSI88, ANSI92, ANSI95 and Telcordia variants.
- The Options parameter is used to active per-circuit options. Allowed values are:
Table SEQ Table \* ARABIC 45 - ISUP circuit options
Circuit options
Description
ANSI International Used to support international calls in addition to national (default). Used for ANSI networks only.
Use Confusion Message Activates the use of the CONFUSION message.
Circuit Type Unknown Indicates circuit group carrier information.
Circuit Type Analog
Circuit Type Digital
Circuit Type Analog Digital
Alarm Carrier Unknown Indicates the information of the alarm carrier.
Alarm Carrier Software
Alarm Carrier Hardware
Continuity Check Unknown Indicates the continuity check requirements. These options can be reconfigured.
Continuity Check None
Continuity Check Statistical
Continuity Check Per Call
- The First CIC parameter indicates the first circuit identification code in the circuit group. This field is used only for ANSI88, ANSI92, ANSI95 and Telcordia. When using one of those variants and receiving (or sending) a group command with a range of 0 (within the “range and status” IE), the ISUP layer uses un16FirstCic and un16NbCircuitInGroup to know which CICs are affected by the command. Refer to section 6.3.3.1 08D0C9EA79F9BACE118C8200AA004BA90B0200000008000 for more information.
- The Number of circuits in group parameter (un16NbCircuitInGroup) indicates total number of CIC part of the circuit group. This field is used only for ANSI88, ANSI92, ANSI95 and Telcordia. When using one of those variants and receiving (or sending) a group command with a range of 0 (within the “range and status” IE), the ISUP layer uses un16FirstCic and un16NbCircuitInGroup to know which CICs are affected by the command. Refer to section 6.3.3.1 08D0C9EA79F9BACE118C8200AA004BA90B020 for more information.
- The Outgoing trunk group nb parameter is used to store the outgoing trunk group number to be used in the EXIT messages for ANSI88, ANSI92, ANSI95 and Telcordia variants for non-SS7 circuits. For SS7 circuits, this field is used to store the circuit ID name for the Telcordia variant.
- The Circuit identification name parameter is used to store the circuit identification name expected in the CVR message. This field is only used for ANSI88, ANSI92, ANSI95 and Telcordia to validate the circuit identification name upon validation of incoming CRV messages. Refer to the ANSI specification for the format of this field.
- The Location ID parameter is contains the common language name to identify the switching office by town, state and building subdivision. This field is only used for ANSI88, ANSI92 and Telcordia variants.
- The Timer configuration parameters are defined as follows; all values must be expressed in milliseconds:
| Connection mode | Description |
|---|---|
| T3 Timer | OVERLOAD message received. Terminated normally after 2 minutes. |
| T12 Timer | BLOCKING message sent. Terminated normally when BLOCKING ACKNOWLEDGEMENT is received. Typical values are 15 to 60 seconds. |
| T13 Timer | INITIAL BLOCKING message sent. Terminated normally when BLOCKING ACKNOWLEDGMENT is received. Typical values are 5 to 15 minutes. |
| T14 Timer | UNBLOCKING message sent. Terminated normally when UNBLOCKING ACKNOWLEDGMENT is received. Typical values are 15 to 60 seconds. |
| T15 Timer | INITIAL UNBLOCKING message sent. Terminated normally when UNBLOCKING ACKNOWLEDGMENT is received. Typical values are 5 to 15 minutes. |
| T16 Timer | RESET message sent. Terminated normally when RELEASE COMPLETE is received. Typical values are 15 to 60 seconds. |
| T17 Timer | INITIAL RESET message sent. Terminated normally when RELEASE COMPLETE is received. Typical values are 5 to 15 minutes. |
| Val Timer | Circuit validation timer for ANSI88, ANSI92, ANSI95 and Telcordia. Typical value is 10 seconds. |
NOTE: The following timers are not required for the UK: T3.
The following enumeration lists the different response parameters and their description:
- The Number of allocated circuit response parameter contains the number of circuits that were successfully allocated. If everything went well, this number should be equal to un32NbCircuitAlloc from the request part of the message (see above).
- The Number of non-allocated circuit response parameter contains the number of unsuccessful allocation attempts. If this number is non-zero, the host application must consider that the value for Number of Circuit Allocated was allocated. Since circuits are allocated sequentially in case of multiple allocations, the host application can assume that the first value for Number of Circuit Allocated was allocated.
NOTE: un32NbCircuitAllocated + un32NbCircuitNotAllocated = un32NbCircuitAlloc
NOTE: As specified in section 6.1.3 08D0C9EA79F9BACE118C8200AA004BA90B0, an ISUP circuit can only be part of a single ISUP interface. On the other hand, multiple circuits can be attached to the same interface instance. Those circuits represent the voice channels available between the local SS7 node and the remote SS7 node.
