1. Feature Guide
  2. DSR Features and Functions
  3. Signaling Transfer Point (STP) Virtual Network Function (VNF)
  4. SCCP -GLOBAL TITLE TRANSLATIONS (GTT) -ANSI/ITU

2.19.3 SCCP -GLOBAL TITLE TRANSLATIONS (GTT) -ANSI/ITU

SCCP -GLOBAL TITLE TRANSLATIONS (GTT) -ANSI/ITU

General

The SCCP Global Title Translations (GTT) feature uses the signaling connection control part (SCCP) to translate addresses (Global Titles) from signaling messages that do not contain explicit information allowing the message transfer part (MTP) to route the message.

Global Title Translation Provisioning

The STP VNF uses tables for performing global title translations. Each table points to another table. The following tables are used for SCCP routing and management.

  • Translation Type (TT) Table
  • Global Title Translation (GTT) Table
  • MAP Table

Translation Type Table

The Translation Type (TT) table is used to direct the translation process to the proper GTT tables for translation and further routing or processing. The Translation Type table supports translation values from 0 to 255.

Global Title Translation Table

The Global Title Translation (GTT) Table contains the digits or ranges of digits that are used to translate the in bound MSU to either another node for additional global title translation (intermediate GTT) or the MSU’s final destination (final GTT). The EAGLE GTT table allows up to 1,000,000 total GTT entries with a performance restriction of up to 200,000 GTT entries per TT. Each entry may be a single value or a range of values

For example, an inbound MSU that arrives with a translation type of 253 and the digits 3038258000 in the CdPA would be translated by the range 3038258-3038259

Table 2-18 Global Title Translation

TT GTA EGTA PC XLAT RI
253 3137070 3137080 1-1-3 DPC GT
253 3137254 3137258 -1-1-4 DPC GT
253 3038258 3038259 1-1-1 DPCSSN SSN
There are five possible results to a global title translation:
  • DPC only, route on GT –This result indicates that the DPC should be altered with the new translated point code, and the message will be routed to that node for further translation. The address indicator routing flag remains set to “route on GT.” If the called party address contains a point code then it is also replaced with the new point code.
  • DPC only, route on SSN –This result indicates that the final destination SSN is already in the called party address and, with the addition of the new translated DPC, the final destination of the message is known. The address indicator routing flag is set to “route on SSN.” The new point code becomes the DPC of the message. If the called party address contains a point code then it is also replaced with the new point code.
  • DPC and SSN, route on SSN –This result indicates that the final destination SSN and DPC should be determined by translation. No further translation is required, and the message can be routed to its final destination. The translated point code is placed into the DPC, and the SSN should be placed in the called party address. The address indicator routing flag is set to “route on SSN.
  • New GT –This result indicates that the translation type in the called party address should be replacedwith the new translation type from the translation. This also indicates that the DPC in the message shouldbe altered with the new translated point code and routed to that node for further translation. The routingindicator flag should remain set at “route on GT.”

MAP Table

The MAP table provides the set of remote subsystems associated to a particular remote point code. Each table contains up to ten subsystems assigned to a particular point code. This table also provides timers used for the subsystem status test (SST) procedure and information for locating the replicated point code and subsystem for any particular SSN. An option is provided on a per point code basis to send an SST upon receipt of an MTP-RESUME to ensure the subsystem is indeed available.

Global Title Translations may result in a choice of up to eight node/subsystems (replicated subsystems). Routing between the replicated pairs is based upon the global title translation results, which are provisioned in the database

There are four routing possibilities:
  • Solitary –the GTT has a single node subsystem
  • Dominant –all traffic is routed to the primary node/subsystem(s) if it is available. If the primary becomes unavailable, the traffic is routed to the backup subsystem(s). If the primary subsequently becomes available again, traffic is then routed back to the primary node/subsystem(s).
  • Load sharing –the load is shared equally between replicated subsystem.
  • Load sharing –the load is shared equally between replicated subsystem.
  • Combination Load Share/Dominant -allows a group of primary node/subsystem(s) to loadshare as a dominant group while having the flexibility to form secondary, tertiary, so on, node or subsystem groups

Advanced Global Title Translation Functionality

The DSR STP VNF provides advanced Global Title Translation functionality to meet specific network needs. The STP VNF provides the following advanced Global Title Translation capabilities:

Flexible GTT Load sharing

The Flexible GTT Load sharing feature enables STP operators to create multiple load-sharing groups using the same destination point codes and/or SubSystem Number. This typically helps applying different load-sharing rules for different traffic types involving the same network elements. Flexible Intermediate GTT Load Sharing.
  • Thanks to the use of Mated Relay Node tables (MRN), the STP will allow multiple load-sharing groups for GT routed traffic (Routing Indicator set to '0')
Flexible Final GTT Load Sharing
  • In case of Final Global Title Translation, Load-sharing rules can differ not only based on theDestination Point Codes but also based on the SubSystem Number of the incoming MSU.Here, the use of multiple Mated Application (MAP) tables will enable full flexibility to the STP operator.

Weighted GTT Load Sharing

This feature allows unequal traffic load-sharing for either Final or Intermediate Global Title Translations. The MAP and MRN tables will offer additional parameters to be provisioned in order to define new rules:
  • Individual weighting for each entity in a relative cost (RC) group.
  • In-service threshold for each RC group.

An RC group is a group of entries in either the MAP or the MRN groups that have the same relative Sucha group can also be referred to as an entity set.

Transaction-Based GTT Load Sharing

Transaction-Based GTT Load Sharing feature allows messages with the same transaction parameters(TCAP, SCCP, MTP...) to be routed to the same destination within an entity set. 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 GTT Load Sharing feature is enabled.
  • A mated relay node (MRNSET) if the Flexible GTT Load Sharing feature is enabled.

The feature applies to the following types of SCCP messages: Class 0/Class 1UDT/UDTS/XUDT/XUDTS.

Different keys derived from the signaling messages can then be used for the load-sharing:
  • 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 Parameters – a combination of the SLS and incoming OPC values.

Flexible Linkset Optional Based Routing

Flexible Linkset Optional Based Routing allows the STP-MP to route GTT traffic based on the incoming link set and to route GTT traffic based on a variety of parameters (MTP, SCCP and TCAP depending onfeatures that are enabled and turned on) in a flexible order on a per-translation basis. This feature enables routing/screening to be performed based on Calling Party information as well as based on the origin linkset from which the message came in the STP. Typically used to differentiate routing/screening rules for international/national gateways from the intra-network linksets.

Flexible Linkset Optional based routing enables new GTTSET Types as follows:

  • GTT Set types for CdPA GTT Selectors:
    • CdPA GTA,
    • CdPA SSDN,
    • DPC
  • GTT Set types for CgPA GTT Selectors:
    • CgPA GTA,
    • CgPA SSN,
    • CgPA PC,
    • OPC

TCAP Opcode Based Routing

TCAP Opcode Based Routing allows the EAGLE to route messages based on their operation codes. The TCAP Opcode Based Routing feature uses the information contained in the TCAP portion of messages(Operation code) is used for performing global title translation. This feature supports both ITU and ANSI messages.

GTT Actions

GTT actions allows ability to do more than just routing and screening the messages in the GTT framework. This enables both black and whitelisting at SCCP layer based on CdPA/CgPA information.

Following actions are supported in STP-MP:

  • DISCARD: Allows silent discard of incoming message. No response is generated.
  • UDTS: Allows to discard the message and generate a UDTS with a customizable SCCP Error Code.
  • TCAP Error: Allows to discard the message and generate response with a customizable TCAP Error Code.
  • FORWARD: Allows to “intercept” signaling traffic and forward it to a different destination than the normal one (if this destination is available).
  • DUPLICATE: Allows message copy over SS7 link done together (or not) with another action. Duplicated messages consume 1 additional ingress MPS.

Please refer Virtual Signaling Transfer Point (vSTP) User's Guide for more details on GTT capabilities.