{
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-21",
  "slug": "rdma-steering-tag",
  "term": "RDMA steering tag",
  "aliases": [
    "STag",
    "Steering Tag"
  ],
  "definition": "A steering tag identifies a tagged memory buffer for access under an RDMA protocol's validity and protection rules.",
  "note": "Addressing: A peer advertises a tagged buffer using an STag, offset and length. The tag identifies memory, not a SCSI logical unit, disk address or authenticated user. [rdmap]\n\nAccess lifetime: A valid tag does not authorize arbitrary memory access; bounds, access rights and the relevant protection context still apply. An invalidation removes remote access through that tag, not the buffer contents. [security]\n\nIn iSER: Normal completion carries a SHOULD recommendation to invalidate the task's advertised STags. Remote invalidation is optional. When an STag is expected to be invalid after task completion, the initiator must check success and invalidate locally if needed. Retaining valid cached tags extends the interval during which remote memory access is possible. [iser]",
  "related": [
    "iser",
    "rdma-storage"
  ],
  "citations": [
    {
      "id": "rdmap",
      "title": "RFC 5040: tagged-buffer terminology and invalidation, sections 2.3-2.4",
      "url": "https://www.rfc-editor.org/rfc/rfc5040.html#section-2.3",
      "accessed": "2026-10-21"
    },
    {
      "id": "security",
      "title": "RFC 5042: buffer access and bounds enforcement, sections 5.4 and 6.2.1",
      "url": "https://www.rfc-editor.org/rfc/rfc5042.html#section-6.2.1",
      "accessed": "2026-10-21"
    },
    {
      "id": "iser",
      "title": "RFC 7145: normal completion, invalidation and security, sections 1.5.1, 8.3.2 and 11",
      "url": "https://www.rfc-editor.org/rfc/rfc7145.html#section-8.3.2",
      "accessed": "2026-10-21"
    }
  ],
  "provenance": [
    "The generic terminology follows RDMAP. Completion and remote-invalidation details here are scoped to iSER."
  ]
}