It does not provide reliable data transfer using sequence numbers and acknowledgements as the default. This sublayer does header checksumming and cell reception. Header Checksum 5-byte header consists of 4 bytes of virtual circuit and control stuff. Checksum 4 bytes of header information and store in 5th byte. Use CRC checksum and add a constant 01010101 bit string.
Upper layers can do payload if they like.
Use idle cells . Exchange control and other information. Cell Reception Drop idle cells , pass along OAM cells. Use a probablistic approach of matching up valid headers and checksums in a 40-bit window. Have a state-transition diagram where we are looking for consecutive valid headers.