A global title (GT) is an address used in the SCCP protocol for routing signaling messages on telecommunications networks.
The structure is usually hierarchical, the value can be of variable length, and is not necessarily a wholly numeric value—though it often is for issues of backward compatibility and association with regular telephone numbers.
The translation type (TT) parameter is used in a network to indicate the preferred method of global title analysis (see below).
In North American mobile networks, different translation types are used for analysis of the IMSI and for messages between telephone systems.
Translation examines the destination address (e.g. the number being called) and decides how to identify it over the telephone network.
The variable length of the global title makes certain optimisations that can be used in IP routing not so easy to use here.
This structure allows for the use of hierarchical routing: In America, the limitations of the North American Numbering Plan mean that the destination country is not immediately obvious from the called party address.
For this reason, the queries have to be routed on the subscriber's identity (IMSI) is used to generate the called party address in the message.
In networks without number portability, it is normal that the MSIN has a structure and that, by analysing the first few digits we can further route the message to the right element.
In this case, due to North American standards, the routing of mobility related messages must be done with the E.212 number directly.