What is Layer 2 Tunneling Protocol (L2TP)

[Ryan21]

Hi,

I know that Layer 2 Tunneling Protocol (L2TP) requires while creating a Virtual private network ?? But what is Layer 2 Tunneling Protocol (L2TP) ?? Can anyone elaborate it this in detail ??

[SergioSantos]

L2TP (Layer 2 Tunneling Protocol) - a network protocol tunneling the link layer, combining the protocol L2F (layer 2 Forwarding), developed by Cisco, and the protocol PPTP Corporation Microsoft. Standard IETF. Allows you to organize VPN with predetermined priorities of access, but does not contain encryption and authentication mechanisms (for creating a secure VPN to use with IPSec).

[TX-Snakebyte]

L2TP, it is being developed and evaluated jointly by Cisco Systems, Microsoft, Ascend, 3Com and other key players in the networking market. It allows encapsulation of PPP packets at layers 2 (Frame Relay and ATM) and 3 (Ip). When configured to transport data over IP, L2TP can be used for tunneling on the Internet. L2TP is based on two concepts: the L2TP access concentrator (LAC: L2TP Access Concentrator) and L2TP network server (LNS L2TP Network Server). L2TP does not incorporate direct protocol for data encryption. Therefore, the IETF recommends the joint use of IPSEC and L2TP.

[PreatORiAn]

Connections L2TP (Layer 2 Tunneling Protocol), also called virtual lines, provide remote users access to low cost, allowing a network server of the company to manage the IP addresses assigned to its remote users. Additionally, L2TP connections provide secure access to your system or network when used in conjunction with IPSec (IP Security). L2TP supports two tunnel modes: the voluntary tunnel and the tunnel required. The most important difference between the two is the end point. In the voluntary tunnel, the tunnel ends at the remote client whereas the compulsory tunnel ends at the ISP.

[electricsketchbook]

The tunneling protocol (encapsulation process for a point-to-point) level 2 (L2TP, Layer Two Tunnel Protocol) was designed to wrap packages PPP (Point-to-Point Protocol) on layers 2 or 3 (IP) of the OSI model. Generally, a level 2 connection is established between a user and a server network access (NAS Network Access Server) connection on which PPP can transport multiple protocols (IP, IPX, AppleTalk, ...) and This a point to point. The NAS is the same endpoint for the connection of level 2 and the PPP session. L2TP can separate these two functions by moving the endpoint of the PPP session in another part of the network will be called or LNS L2TP Network Server. The NAS will then generally the role of LAC and L2TP Access Concentrator. The LAC and LNS are the two ends of the L2TP tunnel that is created to carry PPP sessions to a specified location on the network. Only the LAC and LNS are aware of the L2TP tunnel, the transport of data is therefore the most transparent manner possible for users or applications.

[Samra]

L2TP has been developed based on existing protocols such as PPTP (Point-to-Point Tunnel Protocol) and L2F (Layer Two Forwarding) just to keep the benefits. Thus, it becomes possible to interconnect networks of the same type through a network does not support the protocol used (for example, two non-IP networks can communicate using L2TP via an IP network). This therefore reduces costs by avoiding having to connect to a remote NAS, but rather using a shared infrastructure such as Frame Relay or Internet.

[DllD]

L2TP also meets the expectations for VPNs and security, in fact, used on IP, L2TP allows for tunneling on the Internet and create VPNs. A user can then connect to their corporate network via an L2TP tunnel (with authentication) and then retrieve their profile remote. Moreover, it can be assigned an IP address of the company network. Thus, the IP address management is easier and it avoids unnecessarily burdening the routing tables of the network, the LNS undertaking to aggregate all these addresses to announce prefixes needed.

[Sanith]

One of the main drawbacks of L2TP is the size of its encapsulation. Indeed, the L2TP protocol adds a header of 14 bytes maximum, but if used for tunneling on the Internet, the protocol stack necessary this type of operation brings to 50 the number of extra bytes due to the different successive encapsulations (IP/UDP/L2TP/PPP/IP).