GSMA FS.11 & FS.19 vs GSMA FS.20
GSMA publishes three complementary signaling security specifications. FS.11 covers SS7 message screening at the STP. FS.19 covers Diameter screening at the DEA. FS.20 covers GTP screening at the P-GW / SGSN border. Together they define the modern signaling firewall.
| Attribute | GSMA FS.11 & FS.19 | GSMA FS.20 |
|---|---|---|
| Protocol | FS.11: SS7 · FS.19: Diameter | FS.20: GTP-C / GTP-U |
| Plane | Signaling | Signaling + user |
| Category model | Cat 1 / 2 / 3 by legitimacy | Message-type + IE consistency |
| Placement | STP (SS7) / DEA (Diameter) | P-GW / SGSN / UPF edge |
| Roaming border | International SCCP / IPX | GRX / IPX |
Verdict
FS.11 and FS.19 are the closest thing telecom has to a shared firewall baseline. FS.20 completes the picture on GTP. A "signaling firewall" that implements only one of the three leaves the other two planes wide open — a recurring finding in P1 audits.