Maximum parcel size is determined by which of the two parcel header formats is used. The maximum lengths are shown here:
- When maximum_parcel is 'O':
- buffer size limit: ~32KB
- When maximum_parcel is 'H:'
- buffer size limit: ~64KB (APH-requests is 0)
- When maximum_parcel is 'H:'
- buffer size limit: ~1MB (APH-requests is non-zero)