IL2P (Improved Layer 2 Protocol) is a

data link layer The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer p ...

protocol Protocol may refer to: Sociology and politics * Protocol (politics) Protocol originally (in Late Middle English, c. 15th century) meant the minutes or logbook taken at a meeting, upon which an agreement was based. The term now commonly refers to ...

originally derived from layer 2 of the

X.25 X.25 is an ITU-T standard protocol suite for Packet switched network, packet-switched data communication in wide area network, wide area networks (WAN). It was originally defined by the CCITT, International Telegraph and Telephone Consultative Co ...

protocol suite and designed for use by

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...

operators. It is used exclusively on amateur

packet radio In digital radio, packet radio is the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching Communication protocol, protocol as opposed to circuit switching or message switching protocols ...

networks Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

. IL2P establishes

link layer In computer networking, the link layer is the lowest layer in the Internet protocol suite, the networking architecture of the Internet. The link layer is the group of methods and communications protocols confined to the link that a host is phys ...

connections, transferring data encapsulated in frames between

nodes In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics *Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines, ...

, and detecting errors introduced by the

communications channel A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for inform ...

. The Improved Layer 2 Protocol (IL2P) was created by Nino Carrillo, KK4HEJ, based on

AX.25 AX.25 (Amateur X.25) is a data link layer protocol originally derived from layer 2 of the X.25 protocol suite and designed for use by amateur radio operators. It is used extensively on amateur packet radio networks. AX.25 v2.0 is responsible for e ...

version 2.0 and implements Reed Solomon

Forward Error Correction In computing, telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. The centra ...

for greater accuracy and throughput than either

or FX.25. Specifically, in order to achieve greater stability on link speeds higher than 1200 baud. IL2P can be used with a variety of modulation methods including AFSK and

GFSK Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is encoded on a carrier signal by periodically shifting the frequency of the carrier between several discrete frequencies. The technology is used for c ...

. Th
direwolf
software TNC contains the first open source implementation of the protocol.

IL2P Specification

The IL2P draft specification v0.6 was published via th

on March 16, 2024. As of version 0.6, It added Trailing CRC description. Removed Weak Signal Extensions. Corrected description of block scrambling. Removed reference to Baseline FEC level. Added BPSK and QPSK symbol maps. Updated example encoded packets. Minor edits for readability.

Implementations

IL2P was first implemented in the closed source and proprietary ninoTNC to solve for lossy network links due to low

Signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in deci ...

or weak

signal strength In telecommunications, particularly in radio frequency engineering, signal strength is the transmitter power output as received by a reference antenna at a distance from the transmitting antenna. High-powered transmissions, such as those used i ...

. The specification itself outlines several design goals including: *

Forward error correction In computing, telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. The centra ...

* Eliminating bit-stuffing * Streamlining the

header format * Improved packet detection in the absence of Decode (DCD) and for open-

squelch In telecommunications, squelch is a circuit function that acts to suppress the audio (or video) output of a receiver in the absence of a strong input signal. Essentially, squelch is a specialized type of noise gate designed to suppress weak s ...

receive * Produce a bitstream suitable for modulation on various

physical layer In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechani ...

s * Avoid bit-error-amplifying methods (

differential encoding Differential may refer to: Mathematics * Differential (mathematics) comprises multiple related meanings of the word, both in calculus and differential geometry, such as an infinitesimal change in the value of a function * Differential algebra * ...

and free-running

LFSR In computing, a linear-feedback shift register (LFSR) is a shift register whose input bit is a linear function of its previous state. The most commonly used linear function of single bits is exclusive-or (XOR). Thus, an LFSR is most often a sh ...

s) * Increase efficiency and simplicity over FX.25 Forward Error Correction

References

{{reflist Packet radio Link protocols

IL2P Specification

Implementations

See also

References