Sequenced Unit Header
The Sequenced Unit Header is used for all Cboe Options Auction Feed messages.
Unsequenced data may be delivered using the Sequenced Unit Header. Sequenced headers will have a 0 value for the sequence field and potentially for the unit field.
| Field | Offset | Length | Value/Type | Description |
|---|---|---|---|---|
| Hdr Length | 0 | 2 | Binary | Length of entire block of messages. Includes this header and Hdr Count messages to follow. |
| Hdr Count | 2 | 1 | Binary | Number of messages to follow this header. |
| Hdr Unit | 3 | 1 | Binary | Unit that applies to messages included in this header. |
| Hdr Sequence | 4 | 4 | Binary | Will be zero. |
| Total Length = 8 bytes | ||||