HDLC MSB | LSB Order of bit transmission: bit: 8 7 6 5| 4 3 2 1 The bit 1 is the first bit to be transmitted. +----------|-----------+ octet | Address | 2 |(high order octet) | +----------------------+ octet | Address | 3 |(low order octet) | +----------------------+ octet | Control Base frame formats: 4 | I-frame ,S-frame ,U-frame +----------------------+ octet | Control | 5 | | +- - - - - - - - - - - + . | Information | max. 260 octet . | | +----------|-----------+ FCS+----------------------+ octet | FCS (first octet) | N-2| | +----------------------+ octet | FCS (second octet)| N-1| | +----------------------+ octet | flag | N |0 1 1 1 1 1 1 0| +----------------------+