1. Virtual Signaling Transfer Point User Guide
  2. vSTP Features
  3. Transaction-Based GTT Load Sharing

2.6 Transaction-Based GTT Load Sharing

Transaction-Based GTT Load Sharing allows messages with the same transaction parameters (TCAP, SCCP, MTP, or ENHMTP parameters) to be routed to the same destination within an entity set.

Caution:

This feature is not enabled by default and once it is enabled, it cannot be disabled. To enable it, use MMI, which is described in the MMI API guide under the Vstp: Feature Admin States section.

An entity set is a group of entities that are used to determine the proper destination of a post-GTT message. This group of entities can be one of the following:

  • A mated application (MAP) group
  • A mated relay node (MRN) group
  • A mated application set (MAPSET), if the Flexible GTTLoad Sharing feature is enabled
  • A mated relay node set (MRNSET), if the Flexible GTT Load Sharing feature is enabled.

This feature applies to the following types of SCCP messages:

  • UDT/UDTS class 0 messages
  • UDT/UDTS class 1 messages
  • XUDT/XUDTS class 0 messages
  • XUDT/XUDTS class 1 messages.
UDT/UDTS and XUDT/XUDTS messages are load shared using a key derived from these elements in the message.
  • MTP parameters - the first 3 bytes of the incoming OPC and 1 byte of the SLS.
  • SCCP parameters - the last 4 bytes of the global title address field of the called party address.
  • TCAP parameter - the TCAP Transaction ID in the messages.
  • Enhanced MTP parameter - a combination of the SLS and the incoming OPC values.

SCCP opts can be changed using MMI. Refer to MMI API documentation for updating the SCCP opts parameter. These parameters are:

  • tgtt0 – enable or disable Transaction-Based GTT Load Sharing for SCCP Class 0 UDT, UDTS, XUDT, or XUDTS messages.
  • tgtt1 – enable or disable Transaction-Based GTT Load Sharing for SCCP Class 1 UDT, UDTS, XUDT, or XUDTS messages.
  • tgttudtkey – the Transaction Parameter for the incoming UDT or UDTS messages.
  • tgttxudtkey – the Transaction Parameter for the incoming XUDT or XUDTS messages.

Figure 2-2 describes how the Transaction-Based GTT Load Sharing SCCP options are used.

Figure 2-2 Transaction-Based GTT Load Sharing SCCP Options

Only load shared and combined dominant/load shared entity sets are used to determine the routing for messages that are processed by the Transaction-Based GTT Load Sharing feature.

Using a load shared entity set, the entire entity set is a part of one RC group and the messages are load-shared based on the Transaction Parameter in the entities in the entity set. If none of the entities in the entity set are available for routing, then the message is discarded and a UDTS/XUDTS message is generated if Return on Error is set in the SCCP message. A UIM is generated indicating that the message has been discarded.

Using a combined dominant/load shared entity set, the RC group containing the point code, or point code and SSN, obtained as a result of the global title translation process is used to determine how the message is routed. If none of the entities in this RC group are available for routing, the next higher cost RC group is chosen. This is repeated until an entity in an entity set is available for routing. When an entity is found that is available for routing, the message is routed according to the criteria in that entity. If none of the entities in the entity set are available for routing, the message is discarded. A UDTS/XUDTS message is generated if “Return on Error” is set in the SCCP message. A UIM is generated indicating that the message has been discarded.