Editing IEEE 802.2 (section)

===Control Field===
Following the destination and source SAP fields is a [[HDLC#Control Field|control field]].  IEEE 802.2 was conceptually derived from [[HDLC]], and has the same three types of [[Protocol data unit|PDU]]s:
* unnumbered format PDUs, or '''U-format''' PDUs, with an 8-bit control field, which are intended for connectionless applications;
* information transfer format PDUs, or '''I-format''' PDUs, with a 16-bit control and sequence numbering field, which are intended to be used in connection-oriented applications;
* supervisory format PDUs, or '''S-format''' PDUs, with a 16-bit control field, which are intended to be used for supervisory functions at the LLC (Logical Link Control) layer.

To carry data in the most-often used unacknowledged connectionless mode the U-format is used. It is identified by the value '11' in lower two bits of the single-byte control field.