Hello, my Tectia server is 18.104.22.1688. I have defined a UNC path which is a NAS drive in Virtual folder setting. I use password authentication and the connection is fine that I can access the NAS successfully. However, the file transmission rate is very slow... I have tried to bypass Tectia to transfer the files via FTP or Windows Explorer, the file transmission rate are normal for these channels. May I know what would be the problem of it?
What sort of transfer rates are you seeing?
Can you post some examples for comparison?
Also, what is the ssh client that you are using? If it's Tectia, and you are using the graphical file transfer application you might get better results by using the command line tools. See this question for some examples.
Bear in mind that, depending on how the transfer is being done, there might be a huge overhead with each connection due to the encryption/decryption being performed. Specially if each file that is being transferred, goes through the whole key-exchange, user-authentication, encryption/decryption process. SFTP will never be able to match the performance of FTP or other protocols that lack encryption since they don't have the required overhead that comes with it.
Having said that, you might be able to improve things by switching to faster encryption algorithms or using Tectia client and the connection sharing capabilities that come with it which prevent a new connection being created for each transfer and instead reuse an existing connection if there is one already open.