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 the specs interlock (for example 3GPP TS 33.501 with GSMA FS.34 for 5G SBA security), is essential for both design and audit work.

Telecom networks depend on Internet-style routing (BGP, DNS, MPLS) for interconnect, transport and application delivery. Route hijacks and DNS abuse can degrade or intercept signaling as easily as any application-layer attack, 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, TCP/IP, TTC, ZRES, DetNet and BGP.

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