High Priority Flows Research Articles

Mitigating the impact of controller failures on QoS robustness for software-defined wide area networks

Emerging cloud services and applications pose different Quality of Service (QoS) requirements for the network, where Software-Defined Wide Area Networks (SD-WANs) play a crucial role in QoS provisioning by introducing network programmability into network flows to enable dynamic flow routing and ensure low data transmission latency for these applications. However, controller failures may happen in SD-WANs, and all programmable flows that the failed controller previously controlled will become offline and lose the network programmability, resulting in the degradation of QoS. Existing control recovery solutions propose to remap offline switches/flows to available active controllers but cannot promise good recovery performance due to the following two problems: (1) the recovery performance suffers from either coarse-grained remapping granularity or introducing extra processing delays, and (2) QoS robustness cannot be guaranteed in the design of recovery solution. To this end, we propose Predator, a QoS-aware network programmability recovery scheme that utilizes the P4 Runtime enabled by existing P4 switches to achieve fine-grained per-flow remapping without introducing extra delays. Specifically, our proposed Predator categorizes flows based on their QoS requirements and smartly recovers offline flows based on their priorities to guarantee the QoS robustness for high-priority flows. Simulation results under real-world topology demonstrate that our proposed Predator can improve the recovered network programmability of high-priority flows by up to 505.5%, and substantially reduce the communication overhead of high-priority flows, compared with baselines.

An exergoeconomic-based method for forming water quality pyramid and assessing the sustainability of recycling processes – A greenhouse case study

Recycling is one of the main ways of reducing the consumption of resources (reducing the exergy loss of systems). The economic indices (NPV, IRR, etc.) cannot be used to comprehensively assess the sustainability of the recycling process. For overcoming this challenge, the assessment function of “the saved exergoeconomic cost of production through recycling (ΔExC)“ was developed. For investing in line with sustainability, the high-priority flow for recycling must be distinguished from other flows in the system. Water Quality Pyramid (WQP) was presented based on the unit exergoeconomiccost index (c) to prioritize the flows in the system. The developed method was used to assess the sustainablity of the recycling process in a hydroponic greenhouse producing 725,000 roses cut-flowers in one year, by comparing the two processes for recycling the wastewater of the system to obtain the flows from the top of the greenhouse’s WQP, including the nutritious feed water and desalinated water flows with the c indices of 1168 and 25 USD/GJ. Results show that recycling the drainage of the feed water (Closed-Fertigation process) with the ΔExC value of +2172 USD/a is the sustainable choice, while the ΔExC value for the second flow is negative (−964 USD/a).

Duo: A High-Throughput Reconfigurable Datacenter Network Using Local Routing and Control

The performance of many cloud-based applications critically depends on the capacity of the underlying datacenter network. A particularly innovative approach to improve the throughput in datacenters is enabled by emerging optical technologies, which allow to dynamically adjust the physical network topology, both in an oblivious or demand-aware manner. However, such topology engineering, i.e., the operation and control of dynamic datacenter networks, is considered complex and currently comes with restrictions and overheads. We present Duo, a novel demand-aware reconfigurable rack-to-rack datacenter network design realized with a simple and efficient control plane. Duo is based on the well-known de Bruijn topology (implemented using a small number of optical circuit switches) and the key observation that this topology can be enhanced using dynamic (''opportunistic'') links between its nodes. In contrast to previous systems, Duo has several desired features: i) It makes effective use of the network capacity by supporting integrated and multi-hop routing (paths that combine both static and dynamic links). ii) It uses a work-conserving queue scheduling which enables out-of-the-box TCP support. iii) Duo employs greedy routing that is implemented using standard IP longest prefix match with small forwarding tables. And iv) during topological reconfigurations, routing tables require only local updates, making this approach ideal for dynamic networks. We evaluate Duo in end-to-end packet-level simulations, comparing it to the state-of-the-art static and dynamic networks designs. We show that Duo provides higher throughput, shorter paths, lower flow completion times for high priority flows, and minimal packet reordering, all using existing network and transport layer protocols. We also report on a proof-of-concept implementation of Duo's control and data plane.

Latency control in service chaining using P4-based data plane programmability

Service chaining is becoming one of the most considered service deployment frameworks in the context of Network Function Virtualization (NFV) in edge and data center environments, conveniently supported by automatic connectivity configurations offered by Software Defined Networking (SDN). Current research on the topic is focusing on how to guarantee Quality of Service (QoS) in terms of guaranteed end-to-end latency for time critical services. Indeed, latency issues may depend on intra-server virtualization inefficiencies, leading to Virtual Network Function (VNF) delivery delays, or by congestion events occurring at intermediate network elements connecting VNFs. Latency control requires stateful information such as flow delay measurements at a per-packet level, typically not available at traditional SDN switches or inside the VNF. This paper proposes the adoption of SDN data plane programmability exploiting the P4 language and presents two P4 pipeline solutions, suitable for both intra-rack and inter-rack service chain deployments, to automatically check the path latency experienced by selected high priority flows, also resorting to the recent in-band telemetry applications. The programmable pipelines enforce proactive in-network functions, such as priority change or drop actions, in order to guarantee a bound SFC segment latency delivery, including both the network and the segment VNFs. The proposed solutions are implemented and evaluated in a network testbed employing programmable software switches showing their effectiveness in guaranteeing the configured end-to-end latency, and the limited effort in terms of additional processing at the P4 switch. The evaluation is carried out using the reference P4 software switch, i.e., BMv2. The aim is to validate the full P4 capabilities and the code feasibility in terms of scalability, load and resource impact and added intra-switch latency. The experimental results show the proposed approach scales with the number of forwarded flows and achieves per-segment latency control enforcement in both congested and non-congested scenarios with a very limited impact on the switch extra-latency, exploiting finer per-packet tuning of drop and priority change simply applicable through flow entry configuration. Applicability analysis on hardware switches guaranteeing line rate performance are provided.

Bilateral Teleoperation Performance Model for Network Resource Management

In the forthcoming era of the Tactile Internet, haptic communication is foreseen as one of its major use cases with impact in manufacturing, healthcare, education, as well as the service industry. Recent efforts in networking attempt to meet the requirements of such use cases providing the latency and reliability for bilateral teleoperation, the main component of haptic communication. However, the impact of changes in latency on bilateral teleoperation system performance varies among different control schemes and is dependent on the application domain. Furthermore, while recent efforts to reduce latency in wireless communication with tailored configurations have been successful, an increasing number of haptic communication flows could potentially compete when sharing network resources. In this paper, we provide a tractable model for teleoperation system performance that captures the impact of latency on different performance criteria. We then use this performance model to shape queuing prioritisation of different traffic flows. The proposed framework considers the requirements of high and low priority flows to suggest the best possible control scheme option to be used by the high priority one and at the same time keep the impact of the network scheduling discipline on the low priority one at minimum.

A Priority-Based Multicast Flow Scheduling Method for a Collaborative Edge Storage Datacenter Network

Edge storage, as a supplement to cloud storage, reduces latency by providing services in a timely and efficient manner near the source. In a collaborative edge storage datacenter network (CESN), not only does the edge storage datacenter (ESDC) that is closest to the user provide services, but multiple ESDCs work together to provide better services. In this collaborative work mechanism, different application session requests create large persistent multicast flows with diverse performance requirements. Existing multicast scheduling methods such as unicast shortest path (USP) and static single tree (SST) do not consider flow characteristics or performance requirements. In this paper, we first modeled the multicast flow scheduling problem in a CESN. The model is based on different types of flows with diverse network requirements. Then, we tailored a multicast flow scheduling method based on multiple-attribute decision-making and a genetic algorithm (MDGA). MDGA selects appropriate multicast routing paths for flows in a CESN by considering the requested flow types and network status. The experimental results show that the proposed MDGA method can balance network loads and reduce the average transmission delay for high-priority flows better than USP and SST.

An Optimal Flow Admission and Routing Control Policy for Resource Constrained Networks.

Overloaded network devices are becoming an increasing problem especially in resource limited networks with the continuous and rapid increase of wireless devices and the huge volume of data generated. Admission and routing control policy at a network device can be used to balance the goals of maximizing throughput and ensuring sufficient resources for high priority flows. In this paper we formulate the admission and routing control problem of two types of flows where one has a higher priority than the other as a Markov decision problem. We characterize the optimal admission and routing policy, and show that it is a state-dependent threshold type policy. Furthermore, we conduct extensive numerical experiments to gain more insight into the behavior of the optimal policy under different systems’ parameters. While dynamic programming can be used to solve such problems, the large size of the state space makes it untractable and too resource intensive to run on wireless devices. Therefore, we propose a fast heuristic that exploits the structure of the optimal policy. We empirically show that the heuristic performs very well with an average reward deviation of 1.4% from the optimal while being orders of magnitude faster than the optimal policy. We further generalize the heuristic for the general case of a system with n () types of flows.

HopliteRT: Real-Time NoC for FPGA

With the increasing number of computation nodes integrated in multi and many-core platforms, network-on-chips (NoCs) emerged as a new communication medium in systems-on-chips (SoCs). HopliteRT is a new NoC design that was recently proposed to address the needs of real-time systems whilst respecting the constraints of field-programmable gate array (FPGA) platforms. In this article, we: 1) introduce priority-based routing in HopliteRT; 2) change the network topology in order to improve the packets' worst-case traversal time (WCTT); 3) identify a flaw in the existing timing analysis of HopliteRT; and 4) develop a new timing analysis that is proven correct. We also show by means of experiments that the modifications of HopliteRT proposed in this article allows for at least 2× improvement on the worst and average case traversal time of high priority packets, without impacting the quality of service of low-priority packets. The timing properties of high priority flows are greatly improved for negligible additional hardware costs. The proposed NoC has been implemented in Verilog and synthesized for a Xilinx Virtex-7 FPGA platform.

An efficient priority-driven congestion control algorithm for data center networks

With the emerging diverse applications in data centers, the demands on quality of service in data centers also become diverse, such as high throughput of elephant flows and low latency of deadline-sensitive flows. However, traditional TCPs are ill-suited to such situations and always result in the inefficiency (e.g. missing the flow deadline, inevitable throughput collapse) of data transfers. This further degrades the user-perceived quality of service (QoS) in data centers. To reduce the flow completion time of mice and deadline-sensitive flows along with promoting the throughput of elephant flows, an efficient and deadline-aware priority-driven congestion control (PCC) protocol, which grants mice and deadline-sensitive flows the highest priority, is proposed in this paper. Specifically, PCC computes the priority of different flows according to the size of transmitted data, the remaining data volume, and the flows' deadline. Then PCC adjusts the congestion window according to the flow priority and the degree of network congestion. Furthermore, switches in data centers control the input/output of packets based on the flow priority and the queue length. Different from existing TCPs, to speed up the data transfers of mice and deadline-sensitive flows, PCC provides an effective method to compute and encode the flow priority explicitly. According to the flow priority, switches can manage packets efficiently and ensure the data transfers of high priority flows through a weighted priority scheduling with minor modification. The experimental results prove that PCC can improve the data transfer performance of mice and deadline-sensitive flows while guaranting the throughput of elephant flows.

GRSA: Service-aware flow scheduling for cloud storage datacenter networks

The proliferation of the global datasphere has forced cloud storage systems to evolve more complex architectures for different applications. The emergence of these application session requests and system daemon services has created large persistent flows with diverse performance requirements that need to coexist with other types of traffic. Current routing methods such as equal-cost multipath (ECMP) and Hedera do not take into consideration specific traffic characteristics nor performance requirements, which make these methods difficult to meet the quality of service (QoS) for high-priority flows. In this paper, we tailored the best routing for different kinds of cloud storage flows as an integer programming problem and utilized grey relational analysis (GRA) to solve this optimization problem. The resulting method is a GRAbased service-aware flow scheduling (GRSA) framework that considers requested flow types and network status to select appropriate routing paths for flows in cloud storage datacenter networks. The results from experiments carried out on a real traffic trace show that the proposed GRSA method can better balance traffic loads, conserve table space and reduce the average transmission delay for high-priority flows compared to ECMP and Hedera.

A priority based greedy path assignment mechanism in OpenFlow based datacenter networks

During the past decades, due to the advances of the cloud computing technology with tens of thousands of processing machines, the intra data-center network traffic has increased tremendously. In data-center networks, the typical communication patterns of cloud computing technologies such as map-reduce require short latency of the request and response messages to achieve high service quality. Thus, reducing the latency has been a critical issue in data-center networking. Since latency largely depends on the utilization of the links, it is intuitive that the operators of data-center networks try to maintain the utilization of each link under certain threshold. However, when the network is highly congested, it may not be possible to lower the utilization, which causes that most of the traffic may experience large delay.To overcome such degraded situation, in this paper, we propose a flow priority system, in which flows are divided into two priority types, and the packets of high priority flows are transmitted first. In other words, instead of having the large latency for all traffic flows, at least a large portion of the flows can experience lower latency. We apply the priority system only on the Elephant flows, which are usually software update or data backup messages. Thus all the short flows get high priority. One novel idea of the proposed priority system is that the priority is decided based on the amount of traffic of each link over the path. To be specific, if the assigned path to a flow consists of only low utilized links, the flow is given a high priority. Thus, depending on how to assign a path to a flow, the number of high priority flows varies. If there is no high priority path, the flow is given a low priority. To provide better quality to more flows, i.e., to have more high priority flows, we propose a novel greedy path assignment algorithm called Greedy Flows by exploiting the flexible path computation capability of SDN. We investigate the performance of the proposed algorithm with two baseline algorithms, Global First Fit and Best First Fit. Furthermore we compare the proposed algorithm with Simulated Annealing algorithm, which is a general optimization algorithm, to see how closely the proposed algorithm performs to the optimal. Through extensive simulation, we demonstrate that the proposed algorithm performs much better in path assignment than the two baseline algorithms. Furthermore Greedy Flows performs almost as good as Simulated Annealing.

The results of the experimental study of the Active Queue Management method at the interfaces of telecommunication networks

he paper presents the results of an experimental study of the active queue management method at the interfaces of telecommunication networks. Experimental adequacy and assessment of the effectiveness of the method from the point of view of the main quality of services indicators were carried out at the base of the Cisco Systems laboratory. As a load testing package, the D-ITG package was used to generate and further analyze network traffic. In order to verify the interface bandwidth allocation solutions obtained during the application of the method, they were compared with the WFQ scheduling mechanisms for the average packet delay. To verify the obtained solutions using the active queue management method, they were compared with the AQM WRED mechanisms according to the probability of packet loss. The results of the investigation confirmed the effectiveness of the active queue management method in terms of improving the average packet delay — from 12-17% to 22-25% for high-priority flows (EF, AF41-43) and from 8-12% to 16-19% for low priority flows (AF11-13). Using the active queue management method reduced the probability of packet loss by 7-12% for high-priority flows (EF, AF41-43) and by 10-17% for low-priority flows (AF11-13). It has been established that the recommended area of the practical application of the proposed models for queuing and bandwidth management is the areas of high congestion (more than 80-85%) and congestion of interfaces of telecommunication networks routers, especially in conditions of increased dynamics of their state change.

Transmission Scheduling of Periodic Real-Time Traffic in IEEE 802.15.4e TSCH-Based Industrial Mesh Networks

Time-slotted channel hopping (TSCH) is a part of an emerging IEEE 802.15.4e standard to enable deterministic low-power mesh networking, which offers high reliability and low latency for wireless industrial applications. Nonetheless, the standard only provides a framework, but it does not mandate a specific scheduling mechanism for time and frequency slot allocation. This paper focuses on a centralized scheme to schedule multiple concurrent periodic real-time flows in TSCH networks with mesh topology. In our scheme, each flow is assigned a dynamic priority based on its deadline and the hops remaining to reach the destination. A maximum matching algorithm is utilized to find conflict-free links, which provides more chances to transfer high-priority flows at each time slot. Frequency allocation is implemented by graph coloring to make finally selected links interference free. Simulation results show that our algorithm clearly outperforms the existing algorithms on the deadline satisfaction ratio with a similar radio duty cycle.

Decoupled delay and bandwidth centralized queue-based QoS scheme in OpenFlow networks

There are an increasing of scenarios that require the independent bandwidth and delay demands. For instance, in a data center, the interactive message would not occupy much bandwidth, but it requires the rigorous demands for the delay. However, the existing QoS approaches are mainly bandwidth based, which are inappropriate for these scenarios. Hence, we propose the decoupled scheme in the OpenFlow networks to provide the centralized differential bandwidth and delay control. We leverage the mature HTB to manage the bandwidth. And we design the Queue Delay Management Scheme (QDMS) for queuing delay arrangement, as well as the Comprehensive Parameters based Dijkstra Route algorithm (CPDR) for the propagation delay control. The evaluation results verify the decoupling effectiveness. And the decoupled scheme can reduce the delay for high priority flows.

Performance enhancement of extended AFDX via bandwidth reservation for TSN/BLS shapers

To support mixed-criticality applications, the AFDX may integrate multiple traffic classes: Safety-Critical Traffic (SCT) with hard realtime constraints, Rate-Constrained (RC) traffic requiring bounded latencies and Best Effort (BE) traffic with no delivery constraints. These traffic classes are managed based on a Non-Preemptive Strict Priority (NP-SP) Scheduler, where the highest priority traffic (SCT) is shaped with a Burst Limiting Shaper (BLS). The latter has been defined by the Time Sensitive Networking (TSN) task group to limit the impact of high priority flows on lower priority ones. This paper proposes two bandwidth reservation methods for BLS shapers in AFDX networks. The proposed methods are evaluated on a realistic AFDX configuration. Results show their efficiency to noticeably enhance the RC delay bounds and the SCT schedulability, in comparison to an intuitive method.

Congestion control and packet recovery for cross layer approach in MANET

Mobile Adhoc network is a network, which has advances of dynamic topology, mobility of nodes and congestion control. It is also an infrastructure less networks. This paper “Congestion control and packet Recovery for cross layer approach” is proposed. Traffic of packets occurred due to congestion and contention problems are reduced in datalink layer and transport layer. Also ensuring that, the superior performance of congestion is a challenging model due to changes in link layer contentions, topological changes and characteristic of wireless channel. The features of this model were localized packet recovery, deterministic, ability to trade of efficiency and peer to peer recovery. It can retrieve the missing packets by storing the copy of packet. Also by assigning priority order to the packets, data traffic congestion rate of higher and lower priority packets are maintained. This will develop the high priority flow to get desired access to the medium and its flow rate of low priority is adjusted, in order to have high flow rate of higher priority. Therefore the overall performance gives the better result than existing method. The simulation of CCPRCLA is verified using ns2 simulator, then graph and experimental results are discussed.

Classified Round Robin: A Simple Prioritized Arbitration to Equip Best Effort NoCs With Effective Hard QoS

Advances in semiconductor technology enable integrating tens of cores on a single chip. Providing quality-of-service (QoS) for communication flows in complex embedded applications is critical. In this paper, we present a new approach for designing guaranteed service (GS) networks-on-chip by introducing a new arbitration algorithm and differentiating high and low priority traffic flows in best-effort (BE) networks. An analytical model is provided to compute accurate performance bound parameters in the network with the new arbitration. When the flows have the same priorities in a switch, the new algorithm acts exactly the same as the basic round robin arbitration. It works as a superset of the basic algorithm, when the flows have different priorities. The proposed method helps designers to easily equip traditional BE networks with effective hard QoS, changing it to a GS network. This is done without the need to get involved in the designing complexity of traditional GS networks and still benefit from the superior properties of BE networks. We show substantial improvement in performance bounds for high priority flows (more than 40% in delay and 80% in bandwidth, on average) compared to the known approaches.

QoS oriented dynamic flow preemption (DFP) in MANET

Mobile Ad Hoc Network requires various types of applications’ communication. One of the important is multimedia communication. Such flows demand stringent requirements for Quality of Service. Multimedia or real flows need to book resources such as bandwidth. But in some scenario bandwidth may be occupied by some other resources. In some situation high priority real flows has to wait for resource allocation on a shorter path or may be supplied with another longer path. To overcome such a situation we have provided hop to hop preemption on the basis of number of preemption required on a hop and also by calculating threshold priority difference. In this article, we have proposed Dynamic Flow Preemption (DFP) which will preempt the low priority flow (using some constraints), by another high priority flow. We have evaluated DFP with AdHoc QoS On Demand Routing AQOR. AQOR is considered as it maintains multiple paths like DFP. NS2 simulator is used to compare both the protocols. Result from different parameters and metrics suggest better performance using DFP over AQOR.

Impact Analysis of Flow Shaping in Ethernet-AVB/TSN and AFDX from Network Calculus and Simulation Perspective.

Ethernet-AVB/TSN (Audio Video Bridging/Time-Sensitive Networking) and AFDX (Avionics Full DupleX switched Ethernet) are switched Ethernet technologies, which are both candidates for real-time communication in the context of transportation systems. AFDX implements a fixed priority scheduling strategy with two priority levels. Ethernet-AVB/TSN supports a similar fixed priority scheduling with an additional Credit-Based Shaper (CBS) mechanism. Besides, TSN can support time-triggered scheduling strategy. One direct effect of CBS mechanism is to increase the delay of its flows while decreasing the delay of other priority ones. The former effect can be seen as the shaping restriction and the latter effect can be seen as the shaping benefit from CBS. The goal of this paper is to investigate the impact of CBS on different priority flows, especially on the intermediate priority ones, as well as the effect of CBS bandwidth allocation. It is based on a performance comparison of AVB/TSN and AFDX by simulation in an automotive case study. Furthermore, the shaping benefit is modeled based on integral operation from network calculus perspective. Combing with the analysis of shaping restriction and shaping benefit, some configuration suggestions on the setting of CBS bandwidth are given. Results show that the effect of CBS depends on flow loads and CBS configurations. A larger load of high priority flows in AVB tends to a better performance for the intermediate priority flows when compared with AFDX. Shaping benefit can be explained and calculated according to the changing from the permitted maximum burst.

SatLTP: low extra delay transport protocol for satellite networks

As the exponential growth of traffic patterns with very different characteristics is becoming increasingly common, the high demand for a wide range of services has attracted much attention, e.g. low-priority (LP) service. To satisfy the requirements of LP service for satellite networks, a LP data transfer protocol called satellite networks (SatLTP) with the adaptation to satellite channels and taking advantage of extra bandwidth without interfering high priority flows is proposed. In order to use extra bandwidth adaptable, SatLTP achieves precise adjustment of the congestion window by dynamically updating indicative parameters and selecting optimal window control policies. Simulation results over satellite networks show that SatLTP enhances the throughput of satellite channels in terms of being friendly and non-intrusive toward other protocols (e.g. TCP) and able to effectively exploit the available resources over satellite networks.