To make sure different API clients don't overwrite each other's data, this API supports optimistic concurrency control for any modifications to network lists.
Whenever you run the Get a network list GET operation, your need to retain the value of the response's syncPoint and pass it back in when you subsequently run the Update a network list PUT operation. The update operation only succeeds if there haven't been any interim updates by other API clients. If the update fails, you get a 409 error response.
Note that you only need to pass in the syncPoint value when updating the entire network list object, with or without its complete list of elements. The following operations that only modify the set of elements do not require a syncPoint value:
The response from these operations provide an updated syncPoint value, which you would need for any update to the main network list object, even for a change that doesn't modify the list of elements.