📞SIP Signaling

SIP call signaling metadata, STIR/SHAKEN certificates, and signaling traces attached to a vCon.

Draft: draft-howe-vcon-sip-signaling · Extension name: "sip-signaling"

What it is

A vCon built from a SIP call contains the audio (in dialog) and the parties, but by default loses everything the SIP infrastructure knew about the call — Call-IDs, From/To tags, CSeq numbers, the SDP that negotiated the media, the STIR/SHAKEN certificate chain that authenticated the caller. That metadata matters for fraud investigation, regulatory compliance (TRACED Act), and correlation with carrier-side logs.

The SIP Signaling extension carries that data into the vCon as structured party fields, dialog fields, and attachments.

When to use it

Carrier and enterprise SIP environments where calls flow through SIP recording (SIPREC) or media gateways
TRACED Act / robocall mitigation: STIR/SHAKEN attestation data attached to the vCon
Fraud investigation: correlating vCons with carrier-side CDR / call traces
Operational debugging: keeping the signaling envelope alongside the recording when something went wrong

Spec surface

Party fields

Each party can carry SIP-specific identity and User-Agent info:

{
  "parties": [
    {
      "tel": "+15551234567",
      "name": "Alice",
      "role": "customer",
      "sip": "alice@example.com",
      "sip_contact": "sip:alice@192.0.2.1:5060",
      "sip_user_agent": "ExamplePhone/2.1",
      "sip_display_name": "Alice Anderson"
    }
  ]
}

Dialog fields

Each dialog (call leg) can carry the SIP dialog identifiers:

{
  "dialog": [
    {
      "type": "recording",
      "start": "2026-05-18T14:00:00Z",
      "parties": [0, 1],
      "mediatype": "audio/x-wav",
      "url": "https://example.com/recording.wav",
      "content_hash": "sha512-...",
      "sip_call_id": "a84b4c76e66710@pc33.example.com",
      "sip_from_tag": "1928301774",
      "sip_to_tag": "a6c85cf",
      "sip_cseq": "314159 INVITE"
    }
  ]
}

Signaling attachments

Raw SIP messages, SDP, and STIR/SHAKEN data attach via purpose::

purpose value

Content

sip-invite

The initial INVITE message

sip-response

A SIP response (200 OK, 4xx, etc.)

sip-message-trace

A full message sequence trace

sip-sdp

SDP offer/answer payload

sip-headers

A relevant header subset

stir-certificate

STIR certificate chain (PEM or x5c)

stir-verification-report

Verification result from a STIR validator

stir-passport-extended

Extended STIR PASSporT

{
  "attachments": [
    {
      "purpose": "sip-invite",
      "party": 0,
      "dialog": 0,
      "mediatype": "message/sip",
      "encoding": "none",
      "body": "INVITE sip:bob@example.com SIP/2.0\r\nVia: SIP/2.0/UDP ...\r\n..."
    },
    {
      "purpose": "stir-passport-extended",
      "party": 0,
      "dialog": 0,
      "mediatype": "application/passport+jwt",
      "encoding": "none",
      "body": "eyJhbGciOi..."
    }
  ]
}

Declare the extension at the top level:

{
  "vcon": "0.4.0",
  "extensions": ["sip-signaling"]
}

Working with SIPREC

The vcon-siprec-adapter tool consumes SIPREC-formatted recordings and produces vCons that already include the SIP signaling extension data. If you're ingesting from a SIP recording infrastructure, that adapter is the right starting point — it handles the field mapping for you.