IREG

IREG is the GSMA’s International Roaming Expert Group, and IREG testing is the set of technical tests two operators run before launching roaming with each other. The tests confirm that a subscriber of one network can register on the partner’s network and use voice, SMS and data end to end before real customers depend on it.

The three test stages

GSMA IR.23 organizes international roaming testing in three stages:

Stage	What is tested	How often
Stage 1	Interface self-certification for protocols such as MAP, CAP, Diameter, GTP and HTTP/2	Once per network element type and vendor
Stage 2	Exchange of numbering, addressing and operations data, largely through the IR.21 roaming database	Per partner
Stage 3	End-to-end functional tests with test SIMs in the visited network	Per roaming relationship, repeated when needed

In everyday use, “IREG testing” usually means Stage 3.

Stage 3 test specifications

Stage 3 test cases are defined per technology, including:

• IR.24 — basic voice, SMS and supplementary services.
• IR.35 — GPRS packet data.
• IR.38 — LTE and EPC, including CS fallback and SMS over SGs.
• IR.25 — VoLTE roaming.
• NG.143 — 5G SA roaming.

Typically each operator provides test SIMs to the other, and engineers in the visited country run the cases — registration, outgoing and incoming calls and SMS, data sessions — and record the results.

IREG vs. TADIG

IREG tests prove that roaming works; TADIG testing proves it is billed correctly, by checking the usage records the visited network sends to the home network. IR.23 notes that billing and accounting data can be exchanged alongside the Stage 3 tests, and both kinds of testing are normally completed before commercial launch. See IREG vs TADIG testing.

Why it matters for testing

IREG tests are a launch gate, not a guarantee. Network changes, new radio technologies, steering of roaming policies and core upgrades can all break roaming after launch, which is why IR.23 calls for Stage 3 tests to be repeated as needed. SimCheck.ai runs attach, data, SMS and voice tests on real eSIM profiles in visited networks, on demand or on a recurring schedule — see roaming testing.