HDSL (High-Bit-Rate Digital Subscriber Line)

High-Bit-Rate DSL was an early symmetric DSL technology providing about 1.5 to 2.3 Mbit/s over two copper pairs, used as a cheaper alternative to T1/E1 leased lines. HDSL has been largely superseded by SHDSL, fibre, and Ethernet First Mile, but remains in legacy deployments where re-cabling has not been justified.

Categories: Core NetworkInternet and Routing

HDSL in context

The mobile core carries subscriber sessions, mobility and policy. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF.

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 HDSL in the wider telecom-security picture, review A5/3, Authorization, Core Network, Decryption, SDSL and SCP — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

More from the TelcoSec Glossary

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