SDS is a registry that associates a Subscriber Name and/or Dialled Identity (DID) with one or more Serval Identity (SID). Any subscriber may potentially register with an SDS, and an SDS may also have its own source of registry entries, such as a bound Asterisk exchange. SDS allows the decentralised Distributed Numbering Architechure (DNA) Lookup service to be supplemented with infrastructure, ie, Mesh network nodes offering persistent services or bridges out of the mesh.

• maps Dialled Identity (DID) or Subscriber Name → Serval Identity (SID)
• responds to Distributed Numbering Architechure (DNA) Lookup requests
• keeps registry of Distributed Numbering Architechure (DNA) entries (SID-DID-name)
• accepts registrations and renewals of Distributed Numbering Architechure (DNA) entries
• collects and caches Distributed Numbering Architechure (DNA) responses from local networks

SDS is part of Serval Infrastructure, and allows isolated Mesh networks to be bridged together over other network infrastructure, such as the Internet, satellite up-link, or a data back-haul.