1. Virtual Signaling Transfer Point
  2. Overview of vSTP
  3. Global Title Translation
  4. GTT Routing

2.4.1 GTT Routing

The routing options described in this section allow you to add translations to parameters, code, and components for additional flexibility in routing a message.

TCAP Opcode Based Routing (TOBR)

TOBR provides vSTP with the ability to route messages based on its operation codes. With the TOBR feature, vSTP considers the following information contained in TCAP portion of messages for performing GTT.

  • ITU Messages
    • Message/Package type
    • Application context name
    • Operation code
  • ANSI Messages
    • Package type
    • Operation code family
    • Operation code specifier
  • Message Type support by TOBR for ITU and ANSI
  • ITU TCAP
    • Begin
    • Continue
    • End
    • Abort
    • Unidirectional
  • ANSI TCAP
    • Unidirectional
    • QueryWithPermission
    • QueryWithoutPermission
    • Response
    • ConversationWithPermission
    • ConversationWithoutPermission
    • Abort

TOBR works based on the following rules:

  • If the message/package type is NOT one of those mentioned, vSTP treats it as an unknown message type and does not proceed with the decoding.
  • vSTP attempts to decode the TCAP portion of all UDT/UDTS/Unsegmented XUDT/Unsegmented XUDTS queries coming to the SCCP layer for GTT.
  • If decoding fails, the message still undergoes GTT using some default values for the TCAP data that denote their absence in the message.
  • ACN is used for all supported ITU TCAP messages except ABORT. No attempt to retrieve ACN is made for Abort messages. All other supported messages may have a Dialog portion containing Dialogue Request/Unidirectional Dialogue/Dialogue Response PDU, from which the ACN is retrieved. If no Dialog portion is detected, then ACN is assumed to be NONE.
  • TOBR attempts to find the Operation Code (Opcode) in all supported ITU TCAP messages except ABORT. These messages must contain Invoke or Return Result (Last or Not Last) as the first component. If not, Opcode is assumed to be NONE.
  • TOBR attempts to find the Operation Family and Specifier in all supported ANSI TCAP messages (except ABORT) containing an INVOKE component. For all other messages, Family and Opcode are assumed to be NONE.

Flexible Linkset Optional Based Routing (FLOBR)

FLOBR supports Linkset based routing and Flexible routing.
  • Linkset based routing routes GTT traffic based on the incoming linkset
  • Flexible routing routes GTT traffic based on parameters such as MTP, SCCP, and TCAP in a flexible order on a per translation basis

With the FLOBR feature, you can change the default CdPA GTTSET to point to any GTT set type and find the translation.

FLOBR works based on the following rules:

  1. When GTT mode is FLOBR CDPA, CDPA fields in the MSU are used for GTT selector search and the GTT set is taken from the CDPA GTT SET Name configured in the selector entry.
  2. When GTT mode is FLOBR CGPA, CGPA fields in the MSU are used for GTT selector search and the GTT set is taken from the CGPA GTT SET Name configured in the selector entry.
  3. When GTT hierarchy is FLOBR CDPA and FLOBR CGPA, GTT selectors are searched as defined in 1. If no selector match is found or CDPA GTTSET is not provisioned, GTT selectors are searched as defined in 2.
  4. When GTT hierarchy is FLOBR CGPA and FLOBR CDPA, GTT selectors are searched as defined in 2. If no selector match is found or CGPA GTTSET is not provisioned, GTT selectors are searched as defined in 1.
  5. If GTT selectors are not found as specified in 1, 2, 3 or 4, then vSTP considers this a translation failure.
  6. You can provision a fallback option for each translation in FLOBR to tell it how to route an MSU under the following conditions:
    • Routing when a search fails
    • Routing when the same GTT set name is referred to more than once
    • Limiting the number of database searches to seven (7)
  7. When a fallback option is set to No, the GTT fails and the MSU is discarded.
  8. When a fallback option is set to Yes, the GTT performs based on the last matched entry.

MAP Based Routing (MBR)

MBR provides vSTP with the ability to route messages based on its MAP components. This can be done by using either IMSI or MSISDN GTT set types, which are linked by OPCODE set type.

MBR works based on the following rules:

  • TCAP package types BEGIN, CONTINUE, and END are supported for MAP based routing, so OPTSN with one of the MAP GTT set types are allowed to be provisioned for TOBR GTA entries that have "pkgtype" as BGN, CNT, or END.
  • When an MSU is processed by the TOBR GTT translation with the OPTSN as one of these new set types, Eagle decodes the TCAP part and extracts the required TCAP parameter from the MSU. The digits in this parameter are used as the key to search for the translation in the GTT set.
  • If Dialogue Portion is present in the message, pick the last byte of the ACN.

    Note:

    MBR does not validate if the MAP operation is supported with the ACN in the message; it is only decoding the last byte of the ACN to determine the MAP version.
  • If Dialogue Portion is not present, the MAP version provisioned with the Opcode translation is used as the MAP version.