401 error ,reason=Unauthorized Unknown

Hi All,

I'm using https://xxx.sugarondemand.com/rest/v10/bulk API call to write into SugarCRM.

I'm trying to write a large amount of data to SugarCRM,but after some time,after loading few thousands of records, I'm getting "401 error ,reason=Unauthorized Unknown" as a response.

can anyone please tell me the cause of it??

any help would be appreciated

Thanks