In this section:
Connectionless services are used in a variety of SCCP implementations. In the DSC Platform, SCCP supports both class 0 and class 1 connectionless primitives. Indication messages are sent by SCCP and request messages are sent by the SCCP user application.
The following table lists and describes the SCCP connectionless primitives supported by the DSC Platform.
SCCP Connectionless Primitives
| Message Type | Direction | Description |
|---|---|---|
| N-UNITDATA | Request/Indication | Transfers Unit Data messages (UDT or XUDT), usually containing a TCAP message. |
| N-NOTICE | Request/Indication | Transfer Unit Data service messages (UDTS or XUDTS) which indicates the failure of the associated Unit Data message. |
N-UNITDATA
This primitive is the means by which data is transmitted to and from SCCP user applications on the SS7 network. The following table lists and describes the N-UNITDATA parameters.
N-UNITDATA Parameters
| Parameter | Request | Indication | Description |
|---|---|---|---|
| SCCP-ROUTING-LABEL | M | M | MTP3 routing label. |
| SCCP-CALLED-ADDR | M | M | Called party address. |
| SCCP-CALLING-ADDR | M | M | Calling party address. |
| SCCP-QUALITY-OF-SERVICE | M | O | Quality of service. |
| SCCP-USER-DATA | M | M | User data usually consisting of a TCAP message. |
| SCCP-GWS | O | O | Gateway Screening. |
| SCCP-MSU-TRACING | O | O | MSU Tracing. |
| SCCP-SEGMENT-TOTAL | N/A | O | Number of segments assembled. |
The supported upper bound for N-UNITDATA user data length is 3952 bytes for ITU and 3904 for ANSI and CHINA SS7 variants. These maximum values are good for a called and calling party address length of 3, which is the minimum length.
When the called and calling party addresses are increased by increments of 1, the maximum length of user data must decrease between 1 and 16 bytes, depending on the overall size of the user data length. The maximum user data length is lower if the called and/or calling party address are bigger. This means that the maximum N-UNITDATA size supported is 4002 bytes for ITU and 3954 for ANSI and CHINA.
N-NOTICE
In the event of a failure to reach the final destination using N-UNITDATA, the SCCP sends a N-NOTICE back to the originator of the message including the original data content, stating the cause of the failure. The following table lists and describes the N-NOTICE parameters.
N-NOTICE Parameters
| Parameter | Request | Indication | Description |
|---|---|---|---|
| SCCP-CALLED-ADDR | M | M | Called party address. |
| SCCP-CALLING-ADDR | M | M | Calling party address. |
| SCCP-REASON-FOR-RETURN | M | M | Reason for return. |
| SCCP-USER-DATA | M | M | User data usually consisting of a TCAP message. |
| SCCP-ROUTING-LABEL | M | N/A | MTP3 routing label placed in the outgoing message. |
| SCCP-QUALITY-OF-SERVICE | M | N/A and O | Quality of service. In the indication message, this parameter is N/A for version 6 and lower. In the indication message, this parameter is optional for version 7 and higher. |
| SCCP-GWS | O | O | Gateway Screening. |
| SCCP-MSU-TRACING | O | O | MSU Tracing. |
Overview
Content Tools