Sequenced Unit Header
The Sequenced Unit Header is used for all Cboe Multicast messages as well as messages to and from the Gap Request Proxy (GRP) and Spin Servers.
This feed delivers sequenced and unsequenced data using the Sequenced Unit Header. Unsequenced 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 | Sequence of first message to follow this header. |
| Total Length = 8 bytes | ||||