 If X is one, the Sequence Number field is 48 bits long, and the generic header takes 16 bytes, as follows.If X is zero, only the low 24 bits of the Sequence Number are transmitted, and the generic header is 12 bytes long.Prodrug

A prodrug is a medication or compound that, after administration, is metabolized (i.e., converted within the body) into a pharmacologically active drug.