def body_size(padded=false)
      l = enc_cmd_id.size + payload.size
      padded ? Utils.ceil16(l) : l
    end
def body_size(padded=false)
      l = enc_cmd_id.size + payload.size
      padded ? Utils.ceil16(l) : l
    end
frame-size: 3-byte integer, size of frame, big endian encoded (excludes
 padding)