C# :FTP 上传缓冲区大小

我有FTP上传功能，但有件事我想问它是缓冲区大小，我将其设置为 20KB 这意味着什么，如果我增加/减少它会有所不同吗？

    private void Upload(string filename)
    {
        FileInfo fi = new FileInfo(filename);
        FtpWebRequest ftp = (FtpWebRequest)FtpWebRequest.Create("ftp://" + textBox1.Text + "/" + Path.GetFileName(filename));
        ftp.Credentials = new NetworkCredential(textBox2.Text, textBox3.Text);
        ftp.Method = WebRequestMethods.Ftp.UploadFile;
        ftp.UseBinary = true;
        ftp.KeepAlive = false;
        ftp.ContentLength = fi.Length;
        // The buffer size is set to 20kb
        int buffLength = 20480;
        byte[] buff = new byte[buffLength];
        int contentLen;
        //int totalReadBytesCount = 0;
        FileStream fs = fi.OpenRead();
        try
        {
            // Stream to which the file to be upload is written
            Stream strm = ftp.GetRequestStream();
            // Read from the file stream 2kb at a time
            contentLen = fs.Read(buff, 0, buffLength);
            // Till Stream content ends
            while (contentLen != 0)
            {
                // Write Content from the file stream to the 
                // FTP Upload Stream
                strm.Write(buff, 0, contentLen);
                contentLen = fs.Read(buff, 0, buffLength);
            }
            // Close the file stream and the Request Stream
            strm.Close();
            fs.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Upload Error");
        }
    }