Protocols BroadNet answer

What is an HSS (Home Subscriber Server)?

Last reviewed July 22, 20261 min readReviewed by BroadNet engineering

Quick answer

The HSS (Home Subscriber Server) is the central subscriber database of a 4G LTE / IMS core network — the Diameter-based successor to the 2G/3G HLR. It stores subscriber identities, authentication keys, and service profiles, and answers S6a/S6d signaling from the MME during attach and SMS delivery. On 5G standalone its role passes to the UDM. See /answers/what-is-hlr, /answers/diameter-s6a-explained, and /products/hlr-lookup.

Plain-language definitionVendor-neutralReviewed July 22, 2026

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