INET 4.5.0

This is a new minor stable release within the INET 4.x branch. The main feature of this release is the ability to concurrently run multiple simulations within the same process (requires OMNeT++ 7.0 preview 2 or later), along with an extended Ethernet cut-through switching functionality.

There are also a number of small improvements, and several bug fixes. Some changes are backward incompatible, so existing models may need to be updated. This version requires OMNeT++ 6.0 or later.

For a complete list of all added, removed, and changed folders, NED modules, packet chunks, packet tags, statistics, C++ classes, and signals please refer to the ChangeLog file in the src folder.

Notable backward incompatible changes are the following:

1. Ethernet cut-through switching

   The Ethernet cut-through switching implementation has been extended to work with all TSN traffic filtering and TSN traffic shaping methods. Previously it was not possible to combine these features. For a packet that was forwarded using cut-through switching, the otherwise configured traffic shaping and traffic filtering methods in the switch were completely bypassed.

   The new implementation allows processing the incomplete packet in the switch while the packet buffer is being filled up by the incoming interface. All Ethernet headers are available and the packet length is known, so traffic filtering and traffic shaping can take place the same way it does for store-and-forward packets.

   For more information, see the showcase at: https://inet.omnetpp.org/docs/showcases/tsn/cutthroughswitching/doc/index.html

   This change doesn't require the modification of simulation models, but it may significantly change the statistical results of simulations that use traffic filtering or traffic shaping with cut-through switching.

2. Clock model

   The RandomDriftOscillator module has been refactored to have a more useful parameterization. The module has an initial random drift rate parameter that represents the inaccuracy of device production. Besides, the module uses a random walk process for an additional drift rate change that represents the voltage and temperature dependent inaccuracy of the device.

   Please note that the gPTP time synchronization change (described later) makes the RandomDriftOscillator module more useful than the previously widely used ConstantDriftOscillator module because the first time synchronization can now completely eliminate the effects of a constant drift.

   This change requires the modification of simulation models that use the RandomDriftOscillator module because the parameterization has been changed.

3. Time-Sensitive Networking

   The credit-based shaper has been changed to stop accumulating credits when the corresponding time-aware shaper (same traffic category) transmission gate is closed. Additionally, the credit-based shaper can also stop accumulating credits when the implicit guard band of the time-aware shaper is active.

   The time-aware shaper already provides an implicit guard band before each time a gate is closing according to the gate schedule. This guard band is defined by the following rule: no packet is allowed to pass the gate unless the packet can be transmitted completely before the gate closes.

   This change doesn't require the modification of simulation models, but it may significantly change the statistical results of simulations that use both the credit-based shaper and the time-aware shaper for the same traffic category.

4. Running simulations concurrently (experimental)

   INET has been changed to support running multiple simulations concurrently within a single process. Previously this was not possible, partly because OMNeT++ itself didn't support concurrent simulation execution, but also because INET contained several global variables. Please note that this is an experimental feature in both OMNeT++ and INET.

   In order to provide this feature, global variables have been either eliminated, or replaced with simulation shared variables, or marked with the 'const' qualifier signifying that their values cannot be changed, or marked with the 'OPP_THREAD_LOCAL' macro to store their values separately for each thread.

   This change may require the modification of simulation models if they directly access some of the modified global variables. Additionally, simulation models that have their own global variables must be updated to support running simulations concurrently.

   This feature requires using OMNeT++ 7.0 preview 2 or later. For more information, see the https://omnetpp.org/download/preview page.

Notable backward compatible changes are the following:

1. Clock model

   The clock model has been extended with an oscillator compensation parameter. This parameter can be used to reduce the effect of an inaccurate oscillator on clock time. Time synchronization mechanisms can often estimate the clock speed differences and set this parameter to reduce the clock time difference that would arise over time from clocks running at different speeds.

2. IEEE 802.1-AS (gPTP)

   The gPTP time synchronization protocol has been extended to also compensate for a drifting oscillator. Previously time synchronization only set the clock time but it didn't account for the clock speed differences between the master and the slave clock.

   This change can result in an order of magnitude smaller maximum clock time difference between the master and slave clocks over the period of two time synchronization events.

3. Queueing model

   The behavior of complex queueing models depends among others on the execution order of timers. Previously the scheduling priority for such timers were not configurable, so the user could not control the order of their execution. This limitation could prevent getting the desired behavior from the combination of certain modules. For example, a packet server may need to wait for all gates to open or close before using the scheduler to process the next packet at the same simulation time.

   Several queueing modules have been extended with additional parameters to control the scheduling priority of timers. This gives fine grained control over the order of timer events, that affects how the modules can be combined into more complex behavior.

   Additionally, the active packet source and packet sink modules that generate or consume traffic periodically have been extended with initial offset parameters.

4. IEEE 802.11

   The 802.11 model contains several policy modules that can be replaced by the user to customize the model behavior. For example, the fragmentation policy decides when and how frames should be fragmented. Unfortunately, previously several policy modules were not replaceable using only INI file parameter assignments. This limitation has been fixed.

   All policy submodules have been replaced with submodules having parameterized module types and corresponding module interfaces, making it easy to replace policy submodules using only INI files. Additionally, the documentation of several 802.11 modules and module interfaces have been refined.

5. Protocol element

   The generic protocol elements library have been extended with a protocol independent cut-through implementation. The new modules provide an example of how this mechanism can be implemented and allows teaching and researching this topic.

6. Notable bug fixes and other changes

   • The protocol encapsulation requests and protocol dispatching mechanism between applications, IP, Ethernet, and other protocols have been refactored to use a uniform implementation through utility functions. This provides the user with a more flexible network node architecture where the protocol encapsulation can be decided on a per packet basis.
   • Fixed exponent in the calculation of dielectric obstacle loss.
   • Fixed getReceptionStartTimeVariables method of Z3GateScheduleConfigurator.
   • Fixed processing of Ethernet control frames.
   • Fixed emitting linkBrokenSignal when transmitted packet is not acknowledged.
   • The IPv4NetworkConfigurator log output has been improved.