X.25

X.25 is the ITU-T packet-switching protocol from the 1970s that underpinned many early data networks, including financial and government services. While the public X.25 backbones have been retired, X.25 still appears in some legacy industrial and air-traffic control systems, accessed today via X.25-over-IP (XOT) gateways for backward compatibility.

Categories: Protocols and StandardsInternet and Routing

X.25 in context

Telecom security is written into standards from 3GPP, GSMA, ETSI, IETF and ITU-T. Understanding which body owns which specification, and how they interlock, is essential for both design and audit work.

Telecom networks depend on Internet-style routing (BGP, DNS, MPLS) for interconnect. Route hijacks and DNS abuse can degrade or intercept signaling, which is why RPKI and DNSSEC are now standard hardening for carrier networks.

To place X.25 in the wider telecom-security picture, review 3G, 3GPP, A5/1, BGP, Digital Signature and GSMA Permanent Reference Documents (IR Series) — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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