// IEC 61850-8-1 Edition 2 · GOOSE

📡 GOOSE Message Structure

A complete byte-level breakdown of a Generic Object Oriented Substation Event (GOOSE) frame as defined in IEC 61850‑8‑1 Edition 2. Click any field for details.

🖧

Interactive Frame Map

Ethernet / VLAN
GOOSE Ethertype Header
IEC GOOSE PDU (ASN.1 BER)
Dataset Entries

👆 Click any field below to see a full explanation, byte values, and encoding notes.

Select a field above
—
Click any field in the frame map to see its full description, byte encoding, and example values.
🌳

IECGoosePdu ASN.1 BER Structure

The GOOSE PDU is encoded using Basic Encoding Rules (BER) of ASN.1. Each element is a TLV triplet — Tag · Length · Value. Context tags [0]–[17] map to specific PDU fields.

⏱️

GOOSE Retransmission Timing (Ed. 2)

On a state change, GOOSE messages are retransmitted with exponentially increasing intervals until maxTime is reached, after which they are sent at a fixed heartbeat rate. The StNum increments on state change; SqNum increments on every retransmission.

t STATE CHANGE StNum++, SqNum=0 T0 SqNum=0 +2ms SqNum=1 +4ms +8ms +16ms +32ms intervals double each retransmission maxTime reached (e.g. 1000ms) fixed heartbeat (maxTime interval) Burst retransmissions Heartbeat
TimeAllowedToLive (TAL) — Each GOOSE frame carries a TimeAllowedToLive value (milliseconds). A receiver that does not get the next frame before TAL expires must treat the GOOSE as lost and take appropriate action. TAL is typically set to 2× the current retransmission interval.
📋

PDU Field Reference — IEC 61850‑8‑1 Ed. 2

Field (ASN.1 tag) Tag [hex] M/O Type / Range Description
📝

Key Edition 2 Differences

Security Extension (Ed. 2.1)
IEC 62351-6 adds an optional security footer after the GOOSE PDU: a Signature/MAC or encrypted payload tag. The Ethertype and APPID remain the same; the security tag [0x00] is appended and flagged in the reserved bits.
GSSE Removal
GSSE (Generic Substation Status Events, Ethertype 0x88B8) was present in Edition 1 but removed in Edition 2. All protection tripping now uses GOOSE (0x88B9) exclusively.
confRev Semantics
In Edition 2, confRev must match the GoCB attribute in the SCL file. A receiver detecting a mismatch should raise an alarm — it indicates a reconfiguration that the subscriber has not yet processed.
Simulation Flag (simulation)
The simulation boolean was formally added in Edition 2. When TRUE, receivers in normal service mode must ignore the GOOSE. This enables safe live testing without unwanted relay operation.
VLAN Priority Bits
IEEE 802.1Q VLAN tagging is mandatory for GOOSE in Edition 2. Priority bits (PCP) in the VLAN tag must be set to 4 (recommended) or higher for GOOSE to ensure QoS priority over normal LAN traffic.
ndsCom (Needs Commissioning)
ndsCom is a flag indicating the GoCB is not yet fully commissioned. Receivers shall treat the GOOSE values as unreliable when this bit is set, preventing inadvertent protection operation during setup.