A method of implementing a storage function in a passive optical network system 1, further including a groupcast LINK ID allocation step; in said optical line terminal, allocating a groupcast LINK ID to data requiring storage; and sending {HEAD ~ said data} requiring {TAIL ~ storage} with a broadcast method to all the optical network units 
A method of implementing a storage function in a passive optical network system 1 , further including a groupcast LINK ID allocation step ; in said optical line terminal , allocating a groupcast LINK ID to data requiring storage ; and sending { HEAD ~ said data } requiring { TAIL ~ storage } with a broadcast method to all the optical network units
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