Posted on March 1, 2019


RFC Layer Two Tunneling Protocol “L2TP” (Q). request for comments publication. RFC; Layer Two Tunneling Protocol. Layer Two Tunneling Protocol “L2TP”, August Canonical URL: https://www. ; File formats: Plain Text PDF; Status: PROPOSED. In computer networking, Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to Published in as proposed standard RFC , L2TP has its origins primarily in two older tunneling protocols for point-to-point communication.

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Layer 2 Tunneling Protocol

If set, this data message should receive preferential treatment in its local queuing and transmission. This field exists only if the L bit is set. Another problem is that servers must be specified only by IP address rvc the new Vista configuration utilities; the hostname of the server cannot be used, so if the IP address of the IPsec lt2p changes, all clients will have to be informed of this new IP address which also rules out servers that addressed by utilities such as DynDNS.

With L2TP, a user has an L2 connection to an access concentrator e.

To be useful for networking, higher-level protocols are then run through the L2TP tunnel. PPP defines an encapsulation mechanism for transporting multiprotocol packets across layer 2 L2 point-to-point links. Specifies the number of bytes past the L2TP header at which the payload data is expected to start.


The number of bytes contained in this AVP. This capability can be used to avoid the passing of sensitive data, such as user passwords, as cleartext in an AVP. Indicates the identifier for a session within a tunnel. Internet protocols Internet Standards Tunneling protocols Virtual private networks. L2TP provides reliability features for the control packets, but no reliability for data packets.

Indicates the sequence number expected in the next control message to be received. A secure channel refers to a connection within which the confidentiality of all data is guaranteed. To facilitate this, an L2TP session or ‘ call’ is established within the tunnel for each higher-level protocol such as PPP.

Packets received with an unknown value MUST be discarded. From the end user, packets travel over a wholesale network service provider’s network to a server called a Broadband Remote Access Server BRASa protocol converter and router combined.

Supported L2TP Standards – TechLibrary – Juniper Networks

Any vendor wishing to implement their own L2TP extensions can use their own Vendor ID along with private Attribute values, guaranteeing that they will not collide with any other vendor’s extensions, nor with future IETF extensions. Level 2 tunneling l2t have seen wide use in both small and large networks. Reliability, if desired, must be provided by the nested protocols running within each session of the L2TP tunnel.


Indicates the identifier for the control connection. RFC The variable length concatenation of a unique Attribute represented by an integer and a Value containing the actual value identified by the attribute.

Information on RFC ยป RFC Editor

It may tunnel any protocol carried within PPP. Once a tunnel is established, the network traffic between the peers is bidirectional.

Layer 2 Gfc Protocol DirectAccess. Views Read Edit View history. The control message must then continue to be processed as if the AVP had not been present. The LNS waits for new tunnels. This allows the actual processing of PPP packets to be divorced from the termination of the L2 circuit. ATM access network extensions. This feature is only for use with data messages.

If the M bit is set on an unrecognized AVP within a message associated with the gfc tunnel, the entire tunnel and all sessions within MUST be terminated. Indicates the L2TP protocol version. Multiple AVPs make up Control Messages which are used in the establishment, maintenance, and teardown of tunnels.

The value 1 is reserved to permit detection of L2F packets should they arrive intermixed with L2TP packets.