Is there any limitation about ssh version in remote session

When I running embedded agent in my Ubuntu14.04,  whit openssh server 6.6.1p1,  there is a "version differ" log message.

1. I'm not sure whether this is an error message or warning message, but it seems I cannot  connect the session right. and there is a log message in client side said the "Remote session (id=xxx): removed".

2. Is there really any version matching limitation?