Everything worth knowing, nothing that isn't.
What it actually does
SIGTRAN preserves the SS7 application protocols (MAP, CAP, ISUP, TCAP, SCCP) and replaces only the lower transport layers. Where classic SS7 used MTP1/2/3 over E1 links, SIGTRAN uses adaptation layers (M2PA, M2UA, M3UA, SUA) over SCTP over IP. From the application's perspective — an HLR, an SMSC, an MSC — nothing changes. From the network's perspective, everything changes: signalling now rides leased lines, MPLS, or even the public internet (typically with IPsec).
Why it matters commercially
SIGTRAN is why a new operator can get signalling connectivity in days instead of months. Provisioning a SIGTRAN association requires IP transit and an STP peer agreement; provisioning an old-school SS7 link required physical E1 circuits, line drivers, and a months-long telco install. SIGTRAN reduced SS7 transport cost by an order of magnitude, which is why SS7 message volumes per operator grew 10-100x between 2005 and 2015 — and why SS7 firewalls became a necessity. BroadNet operates SIGTRAN STPs in MENA data centres for SS7 interconnect (/operators/ss7-firewall) and global signalling reach.
Latency, scale, and compliance angle
SIGTRAN latency over a dedicated fibre IP path is comparable to TDM SS7 (single-digit ms within a country, 50-150 ms intercontinental). SCTP's multi-homing means a SIGTRAN association can survive a single ISP failure without dropping signalling. Scale: a single SIGTRAN association can carry tens of thousands of MAP messages per second. Compliance: GSMA FS.07/FS.11 (/answers/gsma-fs07-fs11-signaling-firewall) apply to SIGTRAN exactly as they applied to classic SS7.
Privacy and compliance considerations
SIGTRAN over the public internet without IPsec is a privacy risk — SS7 signalling contains IMSI, MSISDN, location, and routing data that should not be exposed. Modern operators wrap SIGTRAN in IPsec tunnels between peer STPs, or use private MPLS. Cross-border SIGTRAN traffic between operators is in scope for the data-export rules of both jurisdictions (EU GDPR Schrems II, KSA PDPL cross-border transfer rules). Mature operators document each SIGTRAN peer relationship and the legal basis for the data flow.