The parcel APH fields are as follows:
| Field | Purpose |
|---|---|
| PclFlavor (Flavor) | The size remains 2-byte; however, the most significant bit (MSB) of the 2-byte flavor is set to indicate that an alternate parcel header is being sent from the client to the server. |
| PclLength (Length) | Reserved: This is the existing length field in the old parcel header. The size is 2-byte. This field should always be set to zero. |
| PclAltLength (AltLength) | This is the new field of 4-byte size, included in alternate parcel header. The numeric value in this field describes the actual parcel length. |