iphone - NSMutableURLRequest でタイムアウトが正しく機能しません。しかし、なぜ？

Question

NSMutableDictionary* headers = [[[NSMutableDictionary alloc] init] autorelease];
[headers setValue:@"application/x-www-form-urlencoded;charset=utf-8" forKey:@"Content-Type"];
[headers setValue:@"text/html" forKey:@"Accept"];
[headers setValue:@"no-cache" forKey:@"Cache-Control"];
[headers setValue:@"no-cache" forKey:@"Pragma"];
[headers setValue:@"close" forKey:@"Connection"];

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:TIMEOUT_REQUEST];
[request setHTTPMethod:@"POST"];
[request setAllHTTPHeaderFields:headers];
[request setHTTPBody:body];
[self createConnectionWithRequest:request delegate:delegate];

私の TIMEOUT_REQUEST=30 seconds ですが、didFailWithError を取得する前に 80 秒待機することがあります。しかし、なぜ？