S6a

REMORA Category: S

S6a interface is the Diameter-based interface between the MME (Mobility Management Entity) and the HSS (Home Subscriber Server) in 4G LTE networks, defined by 3GPP TS 29.272. It is used for subscriber authentication, location updates, and service-related exchanges. Diameter messages on S6a are carried over SCTP (Stream Control Transmission Protocol), and may also use TCP depending on network configuration.

Messages over S6a Diameter interface

  • Authentication Information Request/Answer (AIR/AIA) – Subscriber authentication
  • Update Location Request/Answer (ULR/ULA) – Notifies HSS of subscriber’s location
  • Notify Request/Answer (NOR/NOA) – Informs of profile changes
  • Purge Request/Answer (PUR/PUA) – Removes inactive subscriber records
  • Delete Subscriber Request/Answer (DSR/DSA) – Deletes subscriber profile
  • Insert Subscriber Info Request/Answer (IDR/IDA) – Updates subscriber data
  • Cancel Location Request/Answer (CLR/CLA) – Removes subscriber location
  • Reset Request/Answer (RSR/RSA) – Resets subscriber-related state

Call Flows

  • Initiated by MME: AIR/AIA, ULR/ULA, NOR/NOA, PUR/PUA
  • Initiated by HSS: DSR/DSA, IDR/IDA, CLR/CLA, RSR/RSA

Transport & Equipment details

  • Diameter itself relies on SCTP or TCP for reliable transport.
  • SCTP is often preferred for its multi-homing and multi-streaming capabilities, aligning with telecom-grade reliability and performance needs.
  • Some Short Message Service Center (SMSC) equipment use Diameter to communicate with the Online Charging System (OCS) for real-time charging of SMS transactions.

yREMORA’s Home Subscriber Server (HSS) products, either yHSS or nHSS, provide comprehensive DIAMETER protocol support across multiple 3GPP interfaces: S6a (MME↔HSS), Cx (CSCF↔HSS), SLh (GMLC↔HSS), S6t (MTC-IWF↔HSS), SWx (3GPP AAA Server↔HSS), and S6c (SMS-GMSC/SMS-IWMSC↔HSS).
yREMORA’s powerful Diameter agents, like yDRA/yDEA or fDRA/fDEA, deliver advanced DIAMETER message routing capabilities based on Application ID, Destination Host, Realm, with support for complex pattern matching and failover scenarios across various network topologies.