if(physical_addrs != null) ret.physical_addrs=(ArrayList)physical_addrs.clone();
    public Object clone() throws CloneNotSupportedException {        LogicalAddress ret=new LogicalAddress(host, physical_addrs);        ret.timestamp=timestamp;        ret.id=id;        ret.additional_data=additional_data;        ret.primary_physical_addr=primary_physical_addr;        return ret;    }