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), a formal agreement between nation states * Protocol (diplomacy), the etiquette of diplomacy and affairs of state * Etiquette, a code of personal behavior Science and technology ...

originally derived from layer 2 of the

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

protocol suite and designed for use by

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

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 protocol as opposed to circuit switching or message switching protocols to transmit digital dat ...

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 occupies the

, the second layer of the

OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...

. It is responsible for establishing link-layer 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 (graph theory), vertex). Node may refer to: In mathematics *Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two ...

, 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 informat ...

. 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 and later occupies t ...

version 2.0 and implements Reed Solomon

Forward Error Correction In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea is ...

for greater accuracy and throughput than either

or FX.25. Specifically, in order to achieve greater stability on link speeds greater 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 transmitted through discrete frequency changes of a carrier signal. The technology is used for communication systems such as telemetry, weather ba ...

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

IL2P Specification

The IL2P draft specification v0.5 was published via th

on June 10, 2022. As of version 0.5, the Weak-Signal-Extensions were added. This adds several features to the protocols. The automatic ID transmission for the FM/1200-baud and faster modes is still in place, but is not enabled if the lower speed SSB modes are selected.

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 the noise power, often expressed in deci ...

or weak

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

. The specification itself outlines several design goals including: *

Forward error correction In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea is ...

* Eliminating

bit-stuffing In data transmission and telecommunication, bit stuffing (also known—uncommonly—as positive justification) is the insertion of non-information bits into data. Stuffed bits should not be confused with overhead bits. Bit stuffing is used for ...

* 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. This layer may be implemented by a PHY chip. The ...

s * Avoid bit-error-amplifying methods (

differential encoding In digital communications, differential coding is a technique used to provide ''unambiguous'' signal reception when using some types of modulation. It makes data to be transmitted to depend not only on the current signal state (or symbol), but also ...

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