Thats a server issue, not changeable on client side.
See: http://www.openbsd.org/cgi-bin/man.cgi?query=sshd_config&apropos=0&sektion=0&manpath=OpenBSD+Current&arch=i386&format=html
See: http://www.openbsd.org/cgi-bin/man.cgi?query=sshd_config&apropos=0&sektion=0&manpath=OpenBSD+Current&arch=i386&format=html
MaxSessions
Specifies the maximum number of open sessions permitted per
network connection. The default is 10.