14.3.1.2.6 Auxiliary Security Header Field

The Auxiliary Security Header specifies information required for security processing and has a variable length. This field determines how the frame is actually protected (security level) and which keying material from the MAC security PIB is used (see IEEE 802.15.4-2006 [2], Section 7.6.1). This field shall be present only if the Security Enabled subfield b3 is set to one. For details of its structure, see IEEE 802.15.4-2006, Section 7.6.2 Auxiliary security header.