Layer 2 Forwarding Protocol
Encyclopedia
L2F, or Layer 2 Forwarding, is a tunneling protocol
developed by Cisco Systems, Inc. to establish virtual private network
connections over the Internet. L2F does not provide encryption
or confidentiality
by itself; It relies on the protocol being tunneled to provide privacy
. L2F was specifically designed to tunnel Point-to-Point Protocol
(PPP) traffic.
prior to 2341 have specified protocols for supporting IP dial-up via SLIP
and multiprotocol dial-up via PPP
.
Tunneling protocol
Computer networks use a tunneling protocol when one network protocol encapsulates a different payload protocol...
developed by Cisco Systems, Inc. to establish virtual private network
Virtual private network
A virtual private network is a network that uses primarily public telecommunication infrastructure, such as the Internet, to provide remote offices or traveling users access to a central organizational network....
connections over the Internet. L2F does not provide encryption
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
or confidentiality
Confidentiality
Confidentiality is an ethical principle associated with several professions . In ethics, and in law and alternative forms of legal resolution such as mediation, some types of communication between a person and one of these professionals are "privileged" and may not be discussed or divulged to...
by itself; It relies on the protocol being tunneled to provide privacy
Privacy
Privacy is the ability of an individual or group to seclude themselves or information about themselves and thereby reveal themselves selectively...
. L2F was specifically designed to tunnel Point-to-Point Protocol
Point-to-Point Protocol
In networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes...
(PPP) traffic.
Use
Virtual dial-up allows many separate and autonomous protocol domains to share common access infrastructure including modems, Access Servers, and ISDN routers. RFCsRequest for Comments
In computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems.Through the Internet Society, engineers and...
prior to 2341 have specified protocols for supporting IP dial-up via SLIP
Serial Line Internet Protocol
The Serial Line Internet Protocol is an encapsulation of the Internet Protocol designed to work over serial ports and modem connections. It is documented in RFC 1055...
and multiprotocol dial-up via PPP
Point-to-Point Protocol
In networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes...
.
L2F packet structure
| Bits 0-12 | 13-15 | 16-23 | 24-31 | ||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| F | K | P | S | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | C | Ver | Protocol | Sequence (opt) | ||||||||||||||||
| Multiplex ID | Client ID | ||||||||||||||||||||||||||||||
| Length | Payload offset (opt) | ||||||||||||||||||||||||||||||
| Packet key (optional) | |||||||||||||||||||||||||||||||
| Payload |
|||||||||||||||||||||||||||||||
| L2F Checksum (opt) | |||||||||||||||||||||||||||||||
Other VPN Protocols
- IPsecIPsecInternet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a communication session...
- L2TP Layer 2 Tunneling Protocol
- OpenVPNOpenVPNOpenVPN is a free and open source software application that implements virtual private network techniques for creating secure point-to-point or site-to-site connections in routed or bridged configurations and remote access facilities. It uses a custom security protocol that utilizes SSL/TLS for...
- PPTP Point-to-Point Tunneling ProtocolPoint-to-point tunneling protocolThe Point-to-Point Tunneling Protocol is a method for implementing virtual private networks. PPTP uses a control channel over TCP and a GRE tunnel operating to encapsulate PPP packets....