padding length (PL)

Padding is a procedure for filling data fields with non- information-relevant binary characters. It is used to ensure prescribed frame lengths, for example in the CSMA/ CD procedure or the IP header.

Some protocols have special padding fields in which the padding length( PL) is entered. If the data stream does not correspond to the specified length, the data field for the padding length must be filled with corresponding fill bits. For the IP protocol, the padding field must be filled up to 32 bits.

Block-oriented encryption methods often work with fixed block lengths, which must also be filled with padding data if the block length falls below the specified length. To ensure that the padding data is not recognized as such, it should be encrypted with the user data.