FTP下载缓慢

Question

我正在使用以下代码从FTP下载文件：

FtpWebRequest request = (FtpWebRequest)WebRequest.Create(downloadPath);
request.UsePassive = false;
request.Method = WebRequestMethods.Ftp.DownloadFile;
request.Credentials = new NetworkCredential(_ftpUser, _ftpPass);
using (var response = (FtpWebResponse)request.GetResponse())
using (var responseStream = response.GetResponseStream())
using (var writer = new FileStream(savePath, FileMode.Create))
{

    long length = response.ContentLength;
    int bufferSize = 2048;
    int readCount;
    byte[] buffer = new byte[2048];

    readCount = responseStream.Read(buffer, 0, bufferSize);
    while (readCount > 0)
    {
        writer.Write(buffer, 0, readCount);
        readCount = responseStream.Read(buffer, 0, bufferSize);
    }

}

它可以工作，但是文件很大，当我使用Filezilla客户端下载文件时，速度要快得多。

这与缓冲区大小有关吗？有什么方法可以使速度更快？