When it comes to computer networking, L2TP Layer 2 Tunneling Protocol (L2TP) happens to be a special tunneling protocol utilized primarily to support and sustain a VPN. It’s not on its own capable of providing you with any kind of encryption / confidentiality. Rather, it will rely primarily on some sort of encryption protocol, which passes inside the tunnel for providing you with sufficient privacy. Though L2TP performs pretty much in the way Data Link Layer type protocols do in the typical OSI model, the truth about L2TP is that, it works like an efficient Session Layer protocol and utilizes registered UDP port (usually port number 1701). That is the bottom line about L2TP VPN. But if you take a look at the OSI Model, it would be clear how that the common examples of the things involved are – Application Layer, Presentation Layer, Session Layer, Transport Layer, Network Layer, Data Link Layer, LLC sublayer and finally – MAC sublayer.
L2TP VPN was originally published back in the 1990s as the projected standard RFC 2661. Speaking the truth, L2TP actually has origins in 2 obsolete tunneling protocols used for PPP. The first one is Layer 2 Forwarding Protocol or L2F for Cisco, while the second one is the PPTP Point-to-Point Tunneling Protocol from US Robotics. The new protocol’s new version was originally published in the mid 1990s as the projected standard RFC 3931. L2TPv3 provide you with extra security features, better encapsulation, and most of all – the capacity for carrying various data links, instead of the obsolete culture of PPP over the IP network (like Frame Relay, Ethernet and ATM).
The whole L2TP packet, which includes payload as well as L2TP header, will be sent into some sort of UDP datagram. It’s pretty common for these systems to bear PPP or Point-to-Point Protocol sessions L2TP VPN tunnels. L2TP doesn’t provide you with any kind of confidentiality and/or sturdy authentication all by itself. Rather, they use IPsec oftentimes to secure their L2TP packets through the providence of confidentiality, authentication and most of all – integrity. The primary combinations of such 2 protocols are generally well-known to be L2TP/IPsec.
These 2 endpoints within the L2TP tunnel generally are known to be the LAC (or L2TP Access Concentrator), whereas the LNS or L2TP Network Server also applies. The LAC happens to be the point where the tunnel initiates, whilst the LNS happens to be the server that waits up for the new tunnels. When the tunnel has been established, the underlying network traffic lying between such peers are actually bidirectional. To make it useful onto any networking environment, they’ll run hi-level protocols that are run subsequently through that L2TP tunnel. For facilitating this, the L2TP session (i.e. L2TP call) will be established inside the tunnel to cater to every hi-level protocol like PPP. This could be very well on the LAC, but the LNS may as well initiate the sessions. Actually, the traffic streaming for every session remains separated by the L2TP. This means that it is entirely possible that you set up numerous virtual networks athwart one single tunnel.