The -X flag to the OpenSSH client enables X11 forwarding. The server must also have support for forwarding enabled.
Source: ssh(1) manpage
Usually, the -Y or -X command line switch will activate X11 tunneling, the -x switch typically disables X11 forwarding.
its backwards
B.UnicastC.KerberosD.Resourse Reservation Protocol(RSVP)
RE
L2tp
The SonicWall VPN client is a hardware based networking device that connects the client with a desired VPN server to build a virtual private network for transferring data over a so called secure VPN-tunnel.
VPN client
Most VPN clients take over the protocol stack by policy, forcing all communications to go through the VPN tunnel. This prevents inadvertant bridging between the protected network represented by the VPN and the unprotected network represented by the actual layer 2/3 connectivity of the client.
The same, tunnel.
Is a tunneling protocol used to support virtual private networks (VPNs) or as part of the delivery of services by ISPs. It does not provide any encryption or confidentiality by itself; it relies on an encryption protocol that it passes within the tunnel to provide privacy. It's also carry common protocol to encapsulation process Point - to - point (PPP). L2TP does not provide confidentiality or strong authentication by itself. L2TP requires that the ISP's routers support the protocol. The L2TP protocol is primarily used to integrate multi-protocol dial-up services into an existing ISP point of presence. The protocol is commonly used for reselling ADSL endpoint and cable network connectivity by sitting between the end-user and the ISP. As a result, the reselling cable provider does not appear to be the one doing the transport.
The world's longest canal tunnel is the Rove Tunnel in France. The Stad Ship Tunnel in Norway is shorter, wider, and deeper.
The Eisenhower Tunnel is the longest vehicular tunnel.