on structured field may be used to carry comments
 or any other type of unarchitected data. Although not recommended,
 it may also be used to carry semantic data in private or exchange data
 streams. However, because receivers of interchange data streams should
 ignore the content of No Operation structured fields and because
 receiver-generator products are not required to propagate
 No Operation structured fields, no semantics should be attached to
 the data carried by the No Operation structured field in