Queue assignment for fixed-priority real-time flows in time-sensitive networks: Hardness and algorithm

Industrial automation, Augmented Reality (AR), Virtual Reality (VR), Robotics, and many other applications need accurate time and data delivery with strict deadlines. The IEEE 802.1 Time-Sensitive Networking (TSN) group defines a set of tools for deterministic communication with high reliability. Although TSN has started from wired (Ethernet) networks, the newer generation wireless technologies, especially Wi-Fi 6/6E and 5G, offer capabilities to extend and enhance TSN operation over the wireless medium. The 3rd Generation Partnership Project (3GPP) Release 16 supports Ultra-Reliable Low-Latency Communications (URLLC) and introduces the capabilities for integrating 5G with TSN networks motivated by the requirements of time-critical industrial systems. This paper presents and evaluates an industrial control system enabled by 5G and TSN capabilities. We describe a TSN over 5G testbed developed with 3GPP Release 15 hardware and discuss the measurement methodology along with Key Performance Indicators (KPIs) required for meeting timing requirements for an industrial control application. We also explore the configuration of TSN over 5G systems and methodologies needed to characterize the Quality of Experience (QoE) for industrial use cases.

Time-Sensitive Networking (TSN) is vital to enable time-critical deterministic communication, especially for applications with industrial-grade requirements. IEEE TSN standards are key enablers to provide deterministic and reliable operation on top of Ethernet networks. Much of the research is still done in simulated environments or using commercial TSN switches lacking flexibility in terms of hardware and software support. In this demonstration, we use an open Cloud testbed for TSN experimentation, leveraging the hardware features that support precise time synchronization, and fine-grained scheduling according to TSN standards. We demonstrate the setup and operation of a Linux-based TSN network in the testbed using our modular Centralized Network Configuration (CNC) controller prototype. With our CNC we are able to quickly initialize the TSN bridges and end nodes, as well as manage their configurations, modify schedules, and visualize overall network operation in real-time. The results show how the TSN features can be effectively used for traffic management and resource isolation.

Ultra-Reliable Low Latency Communication (URLLC) is the current requirement of today's vertical industry as per 3GPP 5G standard such as smart or automotive industry, smart vehicle, smart home, remote surgery for eHealth and cloud robotics for Industry 4.0. These systems are based upon network infrastructure which will handle time critical data traffic. In Release 16, 3GPP has made an integration of the 5G system with IEEE 802.1 working group specifications covering Time Sensitive Networking (TSN). Organizations are presently utilizing this standard in their applications over different wired and wireless networks like ethernet, fiber and 5G networks. In this paper the authors have presented their successful utilization of TSN in their 5G 28 GHz radio link and tested the radio link with different use cases. They are also exploring the different systems available with them starting with PC processor and bluestacks/chromecast software to launch their applications over 5G link. Further, they are exploring the use of multiprocessor based equipments for the upgradation of their system. The inclusion of NPN(Non Public Network) in Release 16 encourages the developers/users to implement their smart 5G network without taking any resources from MNOs (Mobile Network Operator). The authors are emulating NPN and TSN assisted 5G catering for smart system like smart home and vehicle.

Smart substations are an important trend in substation construction. With increasing data traffic, it is difficult for the traditional Ethernet network to meet the real-time requirements of control information in smart substations. Hence, in this paper, a deterministic network architecture for substations based on time-sensitive networks (TSN) has been developed in order to realize the domain-wide time synchronization and efficient real-time communication of the “three-layer and two-network” model in smart substations. Furthermore, a design scheme for substation automation equipment based on TSN is proposed. The proposed device realizes the timely transmission of real-time control information packets by utilizing the Earliest TxTime First (ETF) Qdisc technology of Linux and the timing sending capability of Intel 210 NIC. Furthermore, it collaborates with the time-aware shaper (TAS) traffic scheduling mechanism of TSN switches to ensure the end-to-end deterministic delay of time-sensitive traffic. As a result, it provides efficient real-time communication services with low latency and jitter for smart substation automation systems.

Modern aircraft employ an ever-growing array of sensors, probes, displays, and other high-integrity avionics. This has grown to the point where legacy networking technologies like MIL-STD-1553 and ARINC-429 are no longer sufficient. At the same time, a growing emphasis on Modular Open Standards Approach (MOSA) in defense acquisitions has moved toward favoring more open standards. This presents an opportunity to leverage ubiquitous, high-bandwidth, and flexible Ethernet into an avionics context. The US Army Future Vertical Lift (FVL) initiative presents a key opportunity to realize the advantages of Ethernet for avionics networking by using it as the basis for an avionics Digital Backbone. This paper will evaluate the Certification Readiness, Maturity, and MOSA-Conformance of the Ethernet technologies likely to be featured on FVL aircraft: IEEE 802.3 Best-Effort (BE) Ethernet, Time-Triggered Ethernet (TTE), and IEEE 802.1 Time Sensitive Networking (TSN). All the listed technologies are open Ethernet standards, allowing the system architect to deploy them as needed based on the specific use case and program requirements. This evaluation assesses these three Ethernet technologies on aspects necessary to safely manage flight-critical data over a real-time network, including native fault tolerance, determinism, software dependency, and certifiability. The paper also assesses the technological maturity of each technology in relation to the planned timeline for FVL and evaluates how evolution of the technologies could impact MOSA-conformance. This paper will ultimately recommend a mixed network of a Time-Triggered Ethernet Digital Backbone for high-criticality Air Vehicle System traffic with Best-Effort Ethernet or Time-Sensitive Networking for lower-criticality Mission System traffic.

In order to solve the contradiction between data traffic growth and real-time control information in intelligent substation, this paper proposes a time-sensitive network (TSN)based intelligent substation switch traffic scheduling model, which uses new technologies to dispatch data link layer traffic. This technology adopts the idea of monopolizing and sharing the time slot window for traffic transmission time, using the mechanism of frame preemption in the traffic transmission channel, realizing traffic classification according to the traffic characteristics, and is used to improve the traffic scheduling mechanism of the process layer of the intelligent substation on the traditional switch, improve the effect of determining the time-sensitive traffic delay scheduling, provide traffic transmission services with low latency jitter for the Ethernet network of the intelligent substation, and put forward a new idea for the improvement of the service quality (QoS) of the power system.

A polynomial-time algorithm is presented for partitioning a collection of sporadic tasks among the processors of an identical multiprocessor platform with static-priority scheduling on each individual processor. Since the partitioning problem is easily seen to be NP-hard in the strong sense, this algorithm is not optimal. A quantitative characterization of its worst-case performance is provided in terms of sufficient conditions and resource augmentation approximation bounds. The partitioning algorithm is also evaluated over randomly generated task systems.

The article discuses a number of fundamental results related to determining the maximum output flow in a network after edge failures. On the basis of four theorems, we propose very efficient augmentation algorithms for restoring the maximum possible output flow in a repairable flow network, after an edge failure. In many cases, the running time of the proposed algorithm is independent of the size of the network or varies linearly with the size of the network. The high computational speed of the proposed algorithms makes them suitable for optimising the performance of repairable flow networks in real time and for decongesting overloaded branches in networks. We show that the correct algorithm for maximising the flow in a static flow network, with edges fully saturated with flow, is a special case of the proposed reoptimisation algorithm, after transforming the network into a network with balanced nodes. An efficient two-stage augmentation algorithm has also been proposed for maximising the output flow in a network with empty edges. The algorithm is faster than the classical flow augmentation algorithms. The article also presents a study on the link between performance, topology and size of repairable flow networks by using a specially developed software tool. The topology of repairable flow networks has a significant impact on their performance. Two networks built with identical type and number of components can have very different performance levels because of slight differences in their topology.

software-defined vehicles (SDVs) employ zonal architectures whose zones exchange periodic real-time traffic over a high-speed Time-Sensitive Ethernet (IEEE 802.1Q) backbone. Existing research has produced many deterministic routing schemes for such backbone Ethernet networks, yet has largely ignored the complementary problem of payload-level frame minimization: multiplexing dozens of small zonal messages—whether CAN, LIN, or any other in-zone protocol—into the fewest possible Ethernet frames so that bandwidth, switch buffers and latency budgets are not squandered. This letter concentrates on that neglected frame-minimization facet and presents an optimization flow dedicated to reducing the number of Ethernet frames. We first formulate an exact Satisfiability Modulo Theories (SMTs) model that finds the minimal set of multiplexed frames required across an entire hyper-period. Because SMT becomes intractable on large vehicle topologies, we then introduce a matrix-based heuristic aggregation (MaHA) algorithm that reproduces the SMT’s frame-minimization decisions to within a few percent while executing in milliseconds. Experiments on synthetic SDV workloads show that naive one zonal message per Ethernet frame policies waste significant available payload capacity; our SMT eliminates this waste completely, and the heuristic achieves closely similar savings with up to three orders of magnitude less run-time, making it a practical drop-in solution for next-generation SDV networks.

Global warming trends and the rapid reduction of summer Arctic sea ice extent have increased the feasibility of transarctic transport. How the process of glacier melting affects the existing containerized sea–rail shipping network and container flow assignment has become a challenging economic and policy issue. This paper first examines the meteorological influences on glacier melting and the assignment of container flow over the existing sea–rail network. Then, a three-layer simulation framework is constructed, with the upper layer simulating glacier melting based on the raster grid, the middle layer combining a grid and topology analysis to simulate the evolution of the global sea–rail network and the lower layer establishing a concave cost network flow model to simulate the container flow assignment. Finally, we use MicroCity to achieve the dynamic optimization and simulation of global container flow assignment, solving the large-scale sea–rail shipping network traffic assignment problem. The simulation results show that the proposed model and solution algorithm are feasible and effective, revealing the variation of container flow assignment in the global sea–rail shipping network under different Arctic ice melting scenarios. For instance, in the summer of 2050, the Arctic routes will share the global container flows, resulting in a significant reduction of container flows in the Malacca Strait, Suez Canal and Panama Canal.

To prevent scalability problem caused by increasing traffic of real-time applications, cluster architecture with Time Division Multiple Access (TDMA) scheduling scheme is mostly deployed in wireless sensor networks. However, even though it have proven good scalability and suitability for real-time communications, but static scheduling lacks of adaptability in several situations by not admitting some real-time flows where slots remain available. To solve mentioned problem, in this paper, we propose an adaptive cluster-based scheduling scheme for real-time flows by utilizing the time slots for flows according to type of flows such as inside or outside cluster. So, the proposed scheme can achieve better utilization of channel by minimizing the number of unused channels for real-time flows than static scheme through new adaptive TDMA scheduling scheme . Simulation results show that more flows are admitted and delivered within the deadline in the proposed scheme by utilizing unused time slots accordingly.

We consider a queueing system composed of a dispatcher that routes deterministically jobs to a set of non-observable queues working in parallel. In this setting, the fundamental problem is which policy should the dispatcher implement to minimize the stationary mean waiting time of the incoming jobs. We present a structural property that holds in the classic scaling of the system where the network demand (arrival rate of jobs) grows proportionally with the number of queues. Assuming that each queue of type r is replicated k times, we consider a set of policies that are periodic with period k r pr and such that exactly pr jobs are sent in a period to each queue of type r. When k → ∞, our main result shows that all the policies in this set are equivalent, in the sense that they yield the same mean stationary waiting time, and optimal, in the sense that no other policy having the same aggregate arrival rate to all queues of a given type can do better in minimizing the stationary mean waiting time. This property holds in a strong probabilistic sense. Furthermore, the limiting mean waiting time achieved by our policies is a convex function of the arrival rate in each queue, which facilitates the development of a further optimization aimed at solving the fundamental problem above for large systems.

This paper we consider graphs with reachability restrictions of three types: barrier, valve and magnetic. As a part of the maximum flow problem in networks with considered restrictions, simple examples are given. These examples demonstrate a significant difference between flows in networks with reachability restrictions and flows in the same networks without any reachability restrictions. In each case under consideration there is a decrease of the maximum flow value. Wherein for magnetic reachability it is shown the possibility to control the network flow, whereas for barrier and valve reachability it is shown the reducing of the maximum flow due to the effect of superimposing of flow to itself, which is never observed in the classical theory of flows in networks.

This paper aims the solution of the reroute sequence planning problem for protected traffic flows. This problem arises when a service provider recalculates the path set by a global optimization tool in order to achieve a better resource utilization. In this case a sequence of the one-by-one reconfiguration of the traffic flows from their original paths to the optimized paths has to be found, with the constraint that the link capacities should not be violated at any time during the rerouting process. This optimization problem is related to discrepancy theory and it is NP-complete. It is computationally hard in realworld situations because of the large amount of routers and traffic flows in the network, therefore exact and approximation algorithms have little practical relevance. We present a number of heuristic approaches, which are tested on various network situations. We assume generalized multi-protocol label switching context but the methods can be applied for other types of networks as well. The results show that in most cases these methods are appropriate for calculating the reroute sequence, mainly when the objective of the path optimization is load balancing.

In this demonstration we present MiniNAM, a utility that provides real-time animation of networks created by the Mininet emulator. Mininet is one of the most well-known network emulators in research and academia. Although Mininet is capable of emulating both traditional and software-defined networks, it does not provide a tool to visually observe and monitor the packets flowing over the created network topology. Our utility includes all the components required to initiate, visualize and modify Mininet network flows in real-time. MiniNAM provides a graphical user interface that allows dynamic modification of preferences and packet filters: a user can view selective flows with options to color code packets based on packet type and/or source node. This establishes MiniNAM as a very powerful tool for debugging network protocols or teaching, learning and understanding network concepts. This demonstration illustrates a number of sample use cases and examples of using MiniNAM to create networks and view the generated network flows with customized preferences.