Can't open multiple connections to ssh.net in IIS environment

I am using the ssh.net library to communicate with another server as part of an ASP.NET application.

I noticed that with TCPView to outgoing mail server only one SSH connection, IIS server does not open one SSH connection for every web request as I expected. This causes huge performance problems, as only one request can be processed at a time - and must complete before a new one can be started. Meanwhile, the rest of the requests are pending.

How do I allow the ssh.net library or IIS server to open as many connections as needed?