Rattan and cane is a natural fiber and to make it last, it needs to be taken care of. If it is outdoor furniture, that does not mean that being exposed to the elements 24/7 is a good idea. It is a good idea to buy covers, or have covers made for it. Our South African sun can bake rattan and cane to a crisp.
To clean (indoor or outdoor furniture) brush it down a stiff (not hard) brush. Too hard can cause damage. Work into the overlaps etc to get any accumulated dust out. Vacuum it it to remove any remaining loose dust then wipe it down with a damp cloth.
Protection – teak oil. linseed oil or tung oil. Unless your furniture is dark, rather go with tung oil because tung oil does not darken with age. Tung oil is resistant to water, dust, alcohol, acetone, fruit and vegetable acids.
For more info on which oil for what type of wood, follow this link