This is a new feature release in the INET 4.x branch. Highlights include new protocol implementations for QUIC, Ethernet 10BASE-T1S, IPsec, and MRP; major refinements to the clock model; a reimplementation of IEEE 802.1AS (gPTP); and an important refactoring of the wireless physical layer's analog domain. The release continues to focus on improving correctness, accuracy, modularity, and long-term maintainability while addressing several long-standing limitations. Requires OMNeT++ 6.2 or later.
For the full list of additions, removals, and changes (features, modules, packet chunks/tags, signals, statistics, and C++ classes), see ChangeLog in the src folder.
For further questions, detailed explanations, and guided exploration of INET concepts and features, a dedicated AI-powered wiki is now available at https://deepwiki.com/inet-framework/inet
Notable backward-incompatible changes include the following
1. Clock model refinement
The clock and oscillator models were substantially reworked to improve accuracy, correctness, and robustness. Clock time to simulation time mapping and clock-interval to oscillator-tick conversions were rewritten for mathematical correctness, with stricter consistency checks. Accuracy was improved using precise arithmetic and new scaling utilities (e.g., NumberNear1 and SimTimeScale). The design anticipates future 128-bit simulation time support.
The updated model now accumulates fractional oscillator compensation for more accurate timing. The clock's nominal tick interval must be explicitly configured, as it no longer defaults to the simulation time resolution. The drifting oscillator model was extended with a configurable frequency compensation factor, distinct from the clock's step-based compensation mechanism.
The architecture was modularized to allow multiple clocks to share a single physical oscillator via the clock's oscillatorModule parameter. SettableClock now includes an underlying free-running clock submodule to support simulations that mix synchronized and unsynchronized time. A clock servo model was added, including the IClockServo module interface and the StepClockServo module for implementation.
Clock event handling was also refined: overdue events are now processed immediately, in clock-time order, and newly scheduled events are inserted at the lower bound of the corresponding simulation-time interval, preserving stable ordering. Clock time to simulation time conversion methods now accept explicit lower-bound arguments to ensure robust tie-breaking between adjacent ticks.
Clock and oscillator documentation was significantly expanded and formalized to reflect the stricter semantics of the new implementation.
This change is backward incompatible in that clock-based simulations may produce slightly different statistical results due to the improved correctness and accuracy of the model.
2. IEEE 802.1AS (gPTP) protocol reimplementation
Large parts of the protocol were reimplemented using formal state machines for both peer delay measurement and time synchronization. Standards conformance was improved, including correct handling of grandmaster and neighbor rate ratios. The peer delay and time synchronization processes now maintain separate state for requester/responder and sender/receiver roles.
The new model introduces a dedicated clock servo submodule for updating local time. Peer delay measurements now use an exponential moving average for improved stability and are performed using the unsynchronized local clock to avoid interference during active time synchronization.
For improved standards compliance, message timestamping now occurs at transmission start and reception start rather than at completion. As a result, simulations must use physical layer modules that emit explicit start-of-transmission and start-of-reception signals, such as the StreamingTransmitter and DestreamingReceiver modules.
Due to the high precision required for time synchronization, accurately modeling a 1 ppm clock drift with a nominal 10 ns tick interval requires very fine time granularity. gPTP simulations therefore typically require femtosecond (fs) simulation time resolution, which can be enabled via the simtime-resolution configuration option.
This change is backward incompatible in that simulations using gPTP may produce slightly different statistical results due to the improved correctness and accuracy of the model.
3. Ethernet module renames
Existing Ethernet MAC modules were renamed to use the MacPhy suffix (e.g. EthernetMacPhy, EthernetCsmaMacPhy) to reflect that they combine MAC and PHY functionality in a single module. This resolves naming conflicts introduced by the new dedicated EthernetCsmaMac and EthernetCsmaPhy modules, which provide a modern, state-machine-based implementation of the individual layers and are primarily used by the new Ethernet 10BASE-T1S model.
These changes are backward incompatible for simulations that directly reference the old module names.
4. Wireless physical layer refactoring
The wireless physical layer was significantly refactored to simplify how the analog representation of radio signals is selected. Instead of using separate module types, radio and medium modules now use a signalAnalogRepresentation parameter (unitDisk, scalar, or dimensional) to control their behavior.
Responsibility for computing reception success was partially moved from receiver modules to their analog model submodules. To reflect broader applicability, much of the former UnitDisk-specific implementation was replaced by generic components, resulting in modules such as GenericRadio, GenericTransmitter, and GenericReceiver, while UnitDisk remains available as an analog domain representation.
Specific wireless technologies, including IEEE 802.11, IEEE 802.15.4, and APSK, were refactored to align with the new architecture and can now be used with the unitDisk signal analog representation.
5. CRC, FCS, and Checksum
Frame Check Sequence (FCS) is now used consistently for link-layer protocols (e.g. Ethernet, IEEE 802.11), replacing the generic CRC terminology. Accordingly, crcMode parameters in MAC and radio modules were renamed to fcsMode. In the TCP/IP stack, the term checksum is now used explicitly for 16-bit one’s-complement sums, and crcMode was renamed to checksumMode.
The underlying implementations were modernized as well. New algorithms (CRC32C, CRC16-IBM, CRC16-CCITT) were added, generic and configurable CRC utilities were introduced, and protocol-specific handling was improved—most notably, SCTP now uses a dedicated CRC32C implementation. These changes improve standards compliance, verification reliability, and flexibility while preserving existing behavior by default.
Note that these changes are backward incompatible for simulations that explicitly configure the old crcMode or fcsMode parameters.
Notable backward compatible changes are the following
1. 10BASE-T1S Ethernet physical layer
A 10BASE-T1S Ethernet model was added, implementing Physical Layer Collision Avoidance (PLCA) in accordance with IEEE 802.3cg. The PLCA Reconciliation Sublayer provides deterministic access to the shared medium by assigning transmit opportunities (TOs) to nodes in a round-robin manner, effectively eliminating the collisions typical of CSMA/CD and enabling efficient half-duplex communication.
Unlike traditional point-to-point Ethernet topologies, 10BASE-T1S supports a multidrop bus (mixing segment) in which multiple nodes can be daisy-chained on a single twisted pair without a switch. The model introduces new modules such as EthernetCsmaMac, EthernetPlca, and EthernetCsmaPhy; users should use EthernetPlcaNode for hosts, EthernetPlcaInterface for network interfaces, and EthernetMultidropLink for connectivity.
Several example simulations were added to demonstrate the new functionality.
The 10BASE-T1S protocol implementation was contributed by a generous industry partner.
2. QUIC transport protocol
An implementation of the QUIC transport protocol was added, designed to be structurally modular, and suitable for performance and protocol-level experimentation. It models connection-oriented QUIC over UDP with explicit connection and socket management, supports the full handshake including 0-RTT connection establishment, and provides stream-based data transfer with configurable per-stream and connection-level flow control.
The model includes congestion control with selectable algorithms (e.g. NewReno), loss detection and retransmission with correct handling of ACK-eliciting and non-ACK-eliciting frames, and Path MTU Discovery with optional DPLPMTUD and ICMP Packet Too Big processing. It ensures correct byte ordering and in-order delivery, uses randomized initial destination connection IDs with robust lifecycle management, and supports clean connection teardown with explicit close handling and delayed destruction after CONNECTION_CLOSE.
Validation simulations are integrated into the fingerprint and validation test framework. Overall, the QUIC model provides a solid and extensible foundation for simulating modern UDP-based transport protocols and for comparing their behavior against TCP under controlled conditions.
The QUIC protocol implementation was contributed by Timo Völker.
3. IPsec protocol
The IPv4 model was extended with a comprehensive IPsec implementation to support secure network communication. The model supports both Authentication Header (AH) and Encapsulating Security Payload (ESP), with an emphasis on standards compliance, including correct AH header lengths and proper placement of ESP trailers within encrypted payloads.
The implementation supports UDP traffic and multicast communication, enabling a wide range of secured network scenarios. It also includes protocol-specific packet dissectors and packet printers to allow inspection and analysis of protected traffic.
The IPsec protocol implementation was contributed by Marcel Marek.
4. Media Redundancy Protocol (MRP)
Media Redundancy Protocol (MRP) was added to provide high-availability Ethernet ring redundancy. It improves network reliability by managing redundant paths in ring topologies, preventing loops, and enabling fast recovery after link failures.
The EthernetSwitch module now includes MRP components such as the core protocol logic, redundancy-aware forwarding, a specialized MAC forwarding table, and support for interconnecting multiple rings or redundant segments. The implementation follows the relevant standards, using a specific multicast MAC address for protocol communication and supporting all major MRP message types for topology monitoring and change detection.
Additional signals and statistics were added to improve observability, and the implementation was validated under extreme conditions (e.g. very high packet error rates) to ensure robust recovery behavior.
The MRP protocol implementation was contributed by Daniel Zeitler
5. TCP auto-read mode
The TCP modules were extended with an explicit read mode to support proper TCP flow control. Previously, all TCP sockets operated in auto-read mode, where received data was immediately delivered to the application, effectively disabling flow control.
When explicit read mode is enabled by setting autoRead to false in TcpOpenCommand, applications must issue read requests, similar to real socket read() calls. TCP then delivers buffered or newly arrived data up to a specified byte limit, reducing the advertised window as data arrives and increasing it again only when buffer space is freed by read requests. Auto-read mode remains the default for backward compatibility and continues to advertise the full configured window.
Read requests are represented by TcpReadCommand, and a new request may be issued only after the previous one has been satisfied. In addition, delivery of the TCP_I_PEER_CLOSED indication after a FIN is now delayed until all buffered data has been read by the application.
6. AODV gateway
AODV has been extended to support routing toward external IP networks via a statically configured gateway. By defining the new gatewayAddress parameter, nodes can now handle traffic destined for external addresses by automatically initiating route discovery for the specified gateway. Once the route to the gateway is discovered, external packets are queued and forwarded accordingly.
A showcase was added demonstrating AODV support for routing traffic to external networks via a statically configured gateway, featuring a wireless ad hoc network communicating with a wired Ethernet host through a gateway router.
7. GPSR multiple network interfaces
The GPSR (Greedy Perimeter Stateless Routing) protocol was updated to support simultaneous use of multiple network interfaces, with refactored logic and data structures to track neighbors on a per-interface basis. Beacons are now sent on all configured interfaces, neighbor information stores both position and interface ID, and packet forwarding correctly uses the interface associated with the selected neighbor for greedy or perimeter routing. The internal tables were reorganized by removing unused functionality, renaming PositionTable to GpsrPositionTable, and introducing GpsrNeighborTable.
8. Extended host OS support
The new ExternalEnvironment, ExternalProcess, and ExternalApp modules provide a framework for integrating host OS applications into simulations by managing their execution and setup. ExternalEnvironment handles host configuration via shell commands and is integrated as an optional submodule within NodeBase, while ExternalApp offers a high-level interface to run programs like web servers or routing daemons automatically along with the simulation.
To facilitate host OS isolated emulation, the framework introduces an UnsharedNamespaceInitializer class for creating separate host OS user and network namespaces. A dedicated INITSTAGE_EXTERNAL ensures external devices like TAP interfaces are opened only after the environment is fully prepared.
9. Queueing model
New utility classes have been introduced to replace raw interface pointers with managed references for packet sources and sinks. These classes are PassivePacketSinkRef, ActivePacketSinkRef, PassivePacketSourceRef, and ActivePacketSourceRef, they manage references to components for both push- and pull-based interfaces. Most modules now treat connected sources and sinks as optional, enabling these modules to also connect to non-queueing elements.
Classifiers and schedulers have been extended to enable pulling packets from them and pushing packets to them, respectively. Typically, however, they are used the other way around, with packets being pushed into classifiers and pulled from schedulers.
Several new modules and module interfaces have also been added. For example, the QueueBasedTokenGenerator allows the QueueFiller module to generate traffic that prevents a queue from ever becoming empty.
Statistics collection has been improved across multiple modules. For example, many modules now provide a packetLifeTime statistic; previously, only the bit-based average lifetime (meanBitLifeTimePerPacket) was tracked. The packetLifeTime statistic measures how long a packet stays in the system, from entry to exit. Unlike the older meanBitLifeTimePerPacket, it is a simple per-packet time delta rather than a bit-weighted average, making it easier to interpret, analyze (e.g. histograms, min/max), and align with standard metrics such as end-to-end delay.
In addition, passive packet sinks have been extended with optional statistics to detect duplicate, out-of-order, and missing packets based on packet name index suffixes. To name a few additional statistical changes, the MultiTokenBucketMeter and MultiTokenBucketClassifier modules now record separate statistics for each individual token bucket they contain, and the SlidingWindowRateMeter and ExponentialRateMeter modules now provide packetRate and dataRate statistics.
10. Protocol support
Several smaller modules have been added to support various protocol features.
For example, the GroupEligibilityTimeMeter and GroupEligibilityTimeTable modules were added to support asynchronous traffic shaping with scheduler groups in TSN simulations. The GroupEligibilityTimeMeter provides shared eligibility times for streams within the same group, while GroupEligibilityTimeTable maintains group state and mappings; they are typically connected via Ieee8021qFilter to enforce shared eligibility behavior.
New specialized modules were added to handle Ethernet Frame Check Sequence (FCS) separately, including EthernetFcsHeaderInserter, which inserts Ethernet FCS headers, and EthernetFcsHeaderChecker, which checks and strips Ethernet FCS headers.
Added modules to support the EtherType Protocol Discrimination (EPD) header used by IEEE 802 LLC implementations.
11. Visualizers
The RoutingTableCanvasVisualizer has been extended with a lazy update mechanism that refreshes visualizations only when needed, greatly improving performance. Support for multicast routing tables has been added, along with new filtering parameters to control multicast group, source address, and source node visualization.
The ChannelCanvasVisualizer is a new module for displaying channel activity.
12. Packet serializers
An Ieee802154MacHeaderSerializer has been added to support the binary representation of the IEEE 802.15.4 protocol. In addition, new serializers were introduced for non-standard INET specific protocols or technologies: GenericPhyHeaderSerializer, ShortcutPhyHeaderSerializer, and ShortcutMacHeaderSerializer.
The ApskPhyHeaderSerializer was updated to serialize and deserialize the protocol field using InetPhyProtocolGroup. This change eliminates fingerprint instability caused by serializing internal protocol IDs into the binary representation.
A StreamBufferChunkSerializer was added to enable serialization of frames transmitted using Ethernet cut-through switching.
13. RIP routing tutorial
This tutorial introduces the fundamentals of the Routing Information Protocol (RIP) through a series of progressively complex examples. Starting from static routing baselines, the tutorial demonstrates basic RIP operation with route discovery and convergence, then advances to dynamic scenarios including network failures, recovery mechanisms, and loop prevention techniques. Key distance-vector concepts such as split horizon, triggered updates, route poisoning, and the count-to-infinity problem are explored through hands-on examples.
14. OSPF tutorial
A new multi-step tutorial covers the OSPF (Open Shortest Path First) routing protocol in detail. Beginning with basic single-area configurations featuring adjacency establishment and SPF-based route computation, it progresses through DR/BDR election, link costs, and interface types, then advances to hierarchical multi-area topologies with ABRs, summary LSAs, and external route advertisements. Advanced topics including stub areas, virtual links, and loopback interfaces are also demonstrated.
15. BGP routing tutorial
A comprehensive tutorial guides users through Border Gateway Protocol (BGP) configuration and operation. The tutorial begins with basic E-BGP sessions between autonomous systems with automatic next-hop resolution, then progresses through I-BGP for distributing external routes within an AS, path attributes (AS_PATH, NEXT_HOP, LOCAL_PREF), and multi-hop E-BGP with loopback interfaces. Route redistribution with IGPs (RIP and OSPF), AS configuration, route aggregation, and policy-based filtering are also covered.
16. New showcases
The new tsn/combiningfeatures/fpandtas showcase presents a combined-feature TSN scenario that demonstrates the simultaneous use of Frame Preemption and Time-Aware Shaping (TAS).
The emulation/mininet showcase, based on the VoIP showcase, is now a standalone demonstration of running INET applications within a Mininet environment. It uses an AppContainer-based network structure to connect simulated traffic with external Mininet components.
The emulation/webserver showcase demonstrates the ExternalApp and ExternalEnvironment framework by running a Python-based HTTP server and a wget client as real host OS processes. Network namespaces are used to isolate these external applications while enabling communication through the simulated network.
17. Documentation refinements
NED documentation received extensive improvements in consistency, coverage, and technical accuracy. Brief descriptions were standardized for better presentation in IDE tooltips, terminology and formatting were unified. Documentation was added for many previously undocumented modules. Protocol documentation was expanded and corrected, notably for TCP and gPTP. New or refined material was added for Ethernet (including 10BASE-T1S) and wireless physical layer components.
The User's Guide was revised to use more neutral, professional language. It now includes new documentation on TCP flow control and the effects of the new autoRead parameter. The Developer's Guide was expanded with additional technical diagrams, including a new clock and oscillator model diagram.
Across the documentation, showcases and tutorials were enhanced with “Try It Yourself” sections that provide concrete opp_env commands for interactive experimentation.
18. Notable bug fixes and other changes
- Added INET-specific
SimpleModule,CompoundModule, andModuleMixinas standard bases to derive all modules from. They have adisplayStringTextFormatparameter that supports the old style format directives and alsoWATCHvariable references. Deriving new or existing modules from these bases is optional. - Obsolete
#abstract-config = trueconfiguration options in INI files have been systematically replaced with the now standardabstract = true. - Improved robustness and timing accuracy of the
RealTimeScheduler. Reduced spurious overruns and improved behavior under host load. - Added a
ModuleDumpmodule that can print a module's hierarchy and parameters for debugging and comparison across simulations. OptionalModuleDumpsubmodules were also added toNetworkBase, enabling partial or full network dumps via command line or INI file configuration. - Added
ChannelOwnerRecorder, a result recorder that records which module currently owns a communication channel. Useful for debugging resource contention and validating channel access behavior. Added achannelOwnerstatistic toWireJunctionmodule to record the owning network node in the collision domain. - Added a
SimulationCpuUsageMeasurermodule that measures the CPU time used by a simulation and records it as a scalar statistic. It can be used for performance analysis and benchmarking simulations. - Added parameters to the
MessageDispatchermodule to allow directly controlling the message dispatching mechanism, in contrast with the automatic learning of protocol and interface registrations. - Improved EIGRP stability, cleanup, and modernization. Several bugs were fixed to prevent dangling pointers, handle dynamic neighbor changes correctly, and align IPv4 route removal with IPv6 behavior. Core code paths were refactored to use modern C++ constructs, missing interface parameters were added to improve configurability, and message definitions were simplified, resulting in a more robust and consistent implementation.
- Added a few new NED functions.
seq()returns the next integer (starting from 0) associated with a given string key, enabling deterministic sequences across evaluations.iterate()returns the next value from an array on each evaluation, with the index tracked per context component path. Thepar()function allows dynamic access to module parameters inside expressions. - All module parameters specifying filenames now support substitution, allowing config name, experiment, iteration, run number, etc. to be referenced in the values.
- Added the
DemuxAppFilter, a result filter that de-multiplexes signals by their originating application module, making it easy to record per-application statistics even when applications share a common path or interface. - Added the
DemuxRegexFilter, a result filter that uses regular expression matching on signal metadata or packet names to route incoming data into separate output streams, enabling flexible result categorization based on naming conventions. - Added the
InterarrivalTimeresult filter, which computes the time between consecutive signals or packet arrivals for analyzing jitter, traffic burstiness, and event timing. - Removed the default value
"SSID"for thedefaultSsidparameter inIeee80211AgentSta, requiring users to explicitly configure the SSID for station associations. - The
FlowMeasurementRecorderhas been extended to support recording apacketEventJSON log file, which captures detailed packet-level events during the simulation. - The
SctpAssociationclass is converted into a simple module. - Fixed Ethernet multicast delivery in TSN.
- Fixed mCRC calculation for multi-fragment Ethernet frames.
- The Python support libraries were extended with automatic simulation comparison that identifies the divergence point.
- Converted self-documentation feature into a compile-time option.
- Removed all per-folder ChangeLog files that summarized local changes, since they are no longer useful with current AI tools.
- Several additional issues reported on GitHub have also been fixed.