Subfields in the Options Field
The Options field contains two types of subfields, fixed length and variable length. Certain fixed length subfields do not have any data associated with them and are comprised of a single tag octet. The subfields with data have a single–tag octet, an octet indicating the length, and the data octets.
Table 14.2 describes the fixed length subfields in the Options field.
| Subfield | Tag | Length | Description |
|---|---|---|---|
| Pad | 0 | 1 | Carries no data. It forces the following fields to limit to the preferred boundaries. |
| Subnet mask | 1 | 4 | Denotes the local and network subnet mask. |
| Time offset | 2 | 4 | Indicates the time offset of the subnet from the coordinated universal time (CUT). |
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