Can't upload large file over SFTP (SshOperationTimeoutException)

まず、SftpClient.InternalUploadFile、SftpSession.RequestWrite、Channel.SendData、Session.WaitOnHandle を通るスタックトレースの経路を確認します。報告された所要時間に近い、大容量の SFTP アップロードを再現し、セッションタイムアウトが発生する理由を特定します。転送がタイムアウトせずに完了し、その動作が適切な回帰テストでカバーされれば完了です。

For uploading .csv file over SFTP I use SSH.NET (version 2016.0.0).

The file which needs to be send is rather large (~7GB), and in about an hour after the uploading started it throws the exception Renci.SshNet.Common.SshOperationTimeoutException: Session operation has timed out.

Here is my actual uploading code.

using (SftpClient client = new SftpClient(command.FtpHost, command.UserName, command.Password))
{
    client.Connect();
    client.ChangeDirectory(command.FtpTargetFolder);

    // played a lot with BufferSize property
    // tried to use the default value, tried 4*1024 and 8*1024
    client.BufferSize = 2 * 1024; 

    using (FileStream fileStream = new FileStream(command.LocalFilePath, FileMode.Open))
    {
        client.UploadFile(fileStream, PrepareFileName(command.LocalFilePath));
    }
    client.Disconnect();
}

But this code works fine with smaller (tried with 1-4GB files) files than my desirable one (~7GB). I thought that it could depends on BufferSize, but playing with this property didn't fix the problem.

Here is the issue's stack trace.

Renci.SshNet.Common.SshOperationTimeoutException: Session operation has timed out
at Renci.SshNet.Session.WaitOnHandle(WaitHandle waitHandle, TimeSpan timeout)
at Renci.SshNet.Channels.Channel.GetDataLengthThatCanBeSentInMessage(Int32 messageLength)
at Renci.SshNet.Channels.Channel.SendData(Byte[] data, Int32 offset, Int32 size)
at Renci.SshNet.Sftp.SftpSession.SendRequest(SftpRequest request)
at Renci.SshNet.Sftp.SftpSession.RequestWrite(Byte[] handle, UInt64 offset, Byte[] data, Int32 length, AutoResetEvent wait, Action'1 writeCompleted)
at Renci.SshNet.SftpClient.InternalUploadFile(Stream input, String path, Flags flags, SftpUploadAsyncResult asyncResult, Action'1 uploadCallback)

Also I've noticed that usually uploading throws the error in 1 hour after start and by that time it's uploaded ~80-90% of entire file (because I see not fully uploaded files in my destination SFTP folder).

Does someone has an idea why it's happening?
Btw I've asked StackOverflow question regarding that: http://stackoverflow.com/questions/40158501/cant-upload-large-file-over-sftp
Thanks in advance.