By | February 22, 2019


The term L2TP stands for Layer 2 Tunneling Protocol. This is a protocol which is used by the internet services provider to support the Virtual Private Network (VPN). It is further advancement over the Point to Point Tunneling Protocol (PPTP). The user can establish this type of connection through Admin Login.

Here we will discuss the term L2TP in depth. Thus the readers must check the article to get the details of this protocol.

L2TP Details

The L2TP protocol consists of the best features of two protocols ie PPTP of Microsoft & L2F of Cisco Systems.
There are 2 components of the L2TP protocol. Those 2 components are as follows.

  • L2TP Access Concentrator (LAC).
  • L2TP Network Server (LNS).

All the data packet exchanges take place between these 2 components.

L2TP Working

The L2TP protocol can be used by the user through the User Datagram Protocol (UDP) Port. The structure of the L2TP Data Packet exchange is given below.

As stated in the structure, the L2TP connection uses tunnels to exchange the data packets between the server & client. when the client peers a request then the server provides a specific tunnel & session ID through the control packets. The data packets are then exchanged between the server & client using these tunnels & session ID in the form of PPP (as frame Payload).

Structure of L2TP Packet

The structure of the L2TP Packet consists of the following things

Bits 0–15 Bits 16–31
Tunnel ID Session ID
Flags and Version Info Length (optional)
Ns (optional) Nr (opt)
Offset Size (optional) Offset Pad (optional)
Payload data

Details of various terms are as follows.

Flags and version

Indicates the details of Packet presence of length, Offset fields & sequence.


Indicates length of message or data in bytes.

Tunnel ID

Control connection Identifier.

Session ID

Session Identifier within a tunnel.

Payload data

Variable length (Max payload size = Max size of UDP packet − size of L2TP header)

Advantages of L2TP

Some of the advantages of the L2TP Connection are as follows.

  • It can provide High Data Security for the applications which are critical.
  • High-level encryption to keep data safe.
  • Better effiency & connectivity.
  • Cost Efficient.
  • Reliable in nature.
  • Holds better authorization for VPN authentication.

To get further details, the user can leave a comment below. We will get back to them with the required details as soon as possible.

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