In the IP header there is an option field in which the most diverse options can be entered. The options entered can be identified by their types.
The TLV format stands for an encoding method that comprises a flexible and expandable structure for the encoding parameters within a frame. Type (T) stands for the parameter type, Length (L) for the length of the parameter value and Value (V) for the current parameter value.
The TLV format is used in Basic Encoding Rules (BER) with which data elements are encoded that are used to specify ASN.1 elements as byte strings. It is used in the Link Layer Discovery Protocol (LLDP), among others. It is also used in the Mesh Link Establishment (MLE) protocol to transmit various radio parameters such as the channel characteristics and the received field strength in 802.15.4. These parameters are transmitted as TLV messages independent of the message content.