In information technology, a trailer or footer refers to supplemental data (metadata) placed at the end of a block of data being stored or transmitted, which may contain information for the handling of the data block, or simply mark the block's end.[1]
In data transmission, the data following the end of the header and preceding the start of the trailer is called the payload or body.
It is vital that trailer composition follow a clear and unambiguous specification or format, to allow for parsing. If a trailer is not removed properly, or part of the payload is removed thinking it is a trailer, it can cause confusion.
The trailer contains information concerning the destination of a packet being sent over a network. So for instance, in the case of emails, the destination of the email is contained in the trailer.
