DER Transfer Syntax
Applying an encoding rule to the data structures described by an abstract syntax provides a transfer syntax that governs how bytes in a stream are organized when sent between computers. The transfer syntax used by Distinguished Encoding Rules always follows a Tag, Length, Value format. The format is usually referred to as a TLV triplet in which each field (T, L, or V) contains one or more bytes.
The Tag field specifies the type of the data structure being sent, the Length field specifies the number of bytes of content being transferred, and the Value field contains the content. Note that the Value field can be a triplet if it contains a constructed data type as shown by the following illustration.
See the following topics for detailed information about the components of a TLV triplet.