Everything worth knowing, nothing that isn't.
What it actually does
When an SMSC needs to do an SRI-for-SM against a foreign HLR, it doesn't know the HLR's Point Code — it only knows the recipient MSISDN. The SCCP layer puts the MSISDN (or a derived GT) into the Called Party Address as a GT, and lets the STP do Global Title Translation (GTT): the STP looks up which operator owns that number range, finds the right HLR's Point Code, and forwards the message there. GTT tables at major international STPs are massive — millions of GT-to-PC mappings, updated continuously as number ranges port and operators rebalance.
Why it matters commercially and for security
GT-based routing is the reason cross-operator SS7 works at scale — without it, every SMSC would need to maintain Point Code mappings for every operator in the world. From a security standpoint, GT is also the most common vector for SS7 attacks: an attacker presenting a foreign-operator GT can persuade an STP to route an MAP-SRI-FOR-SM into a target operator's HLR, harvesting the serving MSC and enabling location tracking. SS7 firewalls (/operators/ss7-firewall) cross-check the inbound GT against the peer's IR.21-declared GT range and drop mismatches as FS.07 Category 1 or 2 violations.
Operational angle
GT changes are operationally invisible to the application — your SMSC keeps doing SRI-for-SM by MSISDN, and the STP transparently re-routes when the destination operator changes its GT. The classic failure mode: an STP's GTT table goes stale, a number-range port doesn't get reflected, and your messages start dead-lettering against the wrong operator's HLR. Signalling intelligence platforms (/platforms/signaling-cdr) detect this by correlating SRI-for-SM responses against MNP databases.
Privacy and compliance considerations
Because GT often is an MSISDN, every SS7 message carrying a GT is carrying personal data. GTT tables themselves (which contain ranges, not individual subscribers) are not personal data; the per-message GT in flight is. EU GDPR and KSA PDPL both reach the GT field in SS7 logs once it identifies an individual subscriber. The standard operator response is encrypted storage of signalling logs, role-based access, and aggregation before sharing externally.