ISDN (Integrated Services Digital Network)

Integrated Services Digital Network was the late-1980s digital alternative to analog telephony, offering 64 kbit/s B-channels and a 16 kbit/s D-channel for signalling over the same copper pair. ISDN carried voice, fax, and early dial-up data. It is being switched off worldwide as operators migrate to all-IP voice (VoLTE, SIP trunks) over the next several years.

Categories: SignalingCloud and VirtualizationInternet and Routing

ISDN in context

Signaling protocols carry the control-plane messages that set up calls, register subscribers and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA as top-tier telecom risk.

Moving network functions off dedicated hardware into NFV, Kubernetes and Open RAN reshapes the threat model. Isolation now depends on hypervisor, container and service-mesh controls plus image and Helm-chart supply-chain security.

To place ISDN in the wider telecom-security picture, review Cloud RAN, Exposure Mapping, MUX, Trunk, P-CSCF and S-CSCF — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.