[NSURLSession dataTaskWithRequest] for downloading large files gets halted.

I've got the following code that I use to communicate with a remote server. However, when the response contain a large enough file, the callback block never called, the only thing that trigger the callback, is when I explicitly invoke the cancel method after some timeout from the NSURLSession task (_dataTask).

notice that using tcpdump I did observe that the response was properly received on the client side.

NSURLSessionConfiguration* config = [NSURLSessionConfiguration defaultSessionConfiguration];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
queue.maxConcurrentOperationCount = 1;

NSURLSession* session = [NSURLSession sessionWithConfiguration:config delegate:nil delegateQueue:queue];

_dataTask = [session dataTaskWithRequest:req completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    if ([error code] == NSURLErrorCancelled) {
        writeLog(LOG_ERROR, "NSURLErrorCancelled");
    } else {
        <my completion callback>
    }
}];

[_dataTask resume]

I'd like to know if using dataTask has response size limit (because it's working for small files on response body) and if there is such a limit, so which other method should I use in order to overcome it. I saw that there's an alternative method in NSUrlsession dedicated for downloading files called downloadTaskWithRequest but it doesn't have an async completion block.