IPv6 requires the link maximum transmission unit (MTU) to be at least 1280 octets. In contrast, IEEE 802.15.4's standard frame size is 127 octets. A maximum frame overhead of 25 octets and an optional but highly recommended security feature at the link layer poses an additional overhead of up to 21 octets are for AES-CCM-128.
IPv6 requires a minimum MTU of 1280 octets, while IEEE 802.15.4's frame size is 127 octets. AES-CCM-128 adds an optional but highly recommended security feature with up to 21 octets of overhead for link layer security.