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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This capability can be used to avoid the passing of sensitive data, such as user passwords, as cleartext in an AVP.

From Wikipedia, the free encyclopedia. L2TP allows the creation of a virtual private dialup network VPDN [5] to connect a remote client to its corporate network by using a shared infrastructure, which could be the Internet or a service provider’s network. This feature is only for use with data messages. Reliability, if desired, must be provided by the nested protocols running within each session of the L2TP tunnel.

Also, it is not necessary to open UDP port on firewalls between the endpoints, since the inner packets are not acted upon until after IPsec data has been decrypted and stripped, which only takes place at the endpoints.

RFC – Layer Two Tunneling Protocol “L2TP”

This l2gp exists if the O bit is set. To facilitate this, an L2TP session or ‘ call’ is established within the tunnel for each higher-level protocol such as PPP.

The number of bytes contained in this AVP. Indicates the L2TP protocol version. This field exists only if the L bit is set. The traffic for each session is isolated by L2TP, so it is possible to set up multiple virtual networks across a single tunnel. If the offset field is present, the L2TP header ends after the last byte of the offset padding. Multiple AVPs make up Control Messages which are used in the establishment, maintenance, and teardown of tunnels.


Specifies the number of bytes past the L2TP header at which the payload data is expected to start. To be useful for networking, higher-level protocols are then run through the L2TP tunnel.

If set, this data message should receive preferential treatment in its local queuing and transmission. One peer requests the other peer to assign a specific tunnel and session id through these control packets.

Level 2 tunneling protocols have seen wide use in both small and large networks. If set, the Offset Size field is present. Tunnel ID in each message is that of the intended recipient, not the sender. The term tunnel-mode refers to a channel which allows untouched packets of one network to be transported over another network. Indicates the sequence number expected in the next control message to be received. This page was last edited on 3 Octoberat A secure channel refers to a connection within which the confidentiality of all data is guaranteed.

Windows Vista provides two new configuration utilities that attempt to make using L2TP without IPsec easier, both described in sections that follow below:. The packets exchanged within an L2TP tunnel are categorized as either control packets or data packets.

Then using this tunnel and session id, data packets are exchanged with the compressed PPP frames as payload. PPP defines an encapsulation mechanism for transporting multiprotocol packets across layer 2 L2 point-to-point links.


Layer 2 Tunneling Protocol

ZLB messages are used for explicitly acknowledging packets on the reliable control channel. 2661 is often used to secure L2TP packets by providing confidentiality, authentication and integrity. Once a tunnel is established, the network traffic between the peers is bidirectional.

That is, the same session will be given different Session IDs by each end of the session.

Rather, it relies on an encryption protocol that it passes within the tunnel to provide privacy. L2TP does not provide confidentiality or strong authentication by itself.

In such a configuration, the L2 termination point and PPP session endpoint rgc on the same physical device i. Views Read Edit View history. Any rfv 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.

Internet protocols Internet Standards Tunneling protocols Virtual private networks.

RFC Layer Two Tunneling Protocol “L2TP” – Wikidata

RFC The variable length concatenation of a unique Attribute represented by an integer and a Value l2tl the actual value identified by the attribute. Because of the lack of confidentiality inherent in the L2TP protocol, it is often implemented along with IPsec. The value 1 is reserved to permit detection of L2F packets should they arrive intermixed with L2TP packets.

The control message must then continue to be processed as if the AVP l2p not been present. Layer 2 Forwarding Protocol DirectAccess.