Deficit Round Robin Research Articles

Performance modelling and analysis of Deficit Round Robin scheduling scheme with self‐similar traffic

AbstractThe provisioning of fairness to various network applications is an important Quality‐of‐Service demand and has thus become a challenging research issue in contemporary communication networks. Deficit Round Robin (DRR) is a promising fair scheduling mechanism owing to its low complexity and excellent ability of achieving a good degree of fairness in terms of throughput. On the other hand, self‐similar traffic was found to be pervasively present in communication networks and has great impact on the performance of scheduling systems. However, to the best of our knowledge, there has not been any analytical model reported in the open literature for the DRR mechanism in the presence of self‐similar traffic. To fill this gap, this paper analytically investigates the queueing performance of DRR and develops a new analytical model for deriving the upper and lower bounds of the queue length distributions of individual traffic flows in DRR scheduling systems subject to self‐similar traffic. Extensive comparison between simulation and analytical results validates the accuracy of the developed model. To demonstrate its applications, the analytical model is used to investigate the effects of packet size on the performance of the queueing system. The developed model is further applied to study the configuration of weights of individual traffic flows. Copyright © 2010 John Wiley & Sons, Ltd.

Modeling and resource allocation for mobile video over WiMAX broadband wireless networks

The key to proper resource allocation for mobile video on wireless networks is to have a good model for the resource demands. In this paper, we present the results of analysis of a number of mobile video streams and show that a simple seasonal ARIMA model (SAM) can provide a very good representation for both MPEG4-Part2 and MPEG4-Part10 videos, the formats that are commonly used for mobile videos. The model has been implemented to provide both video frame and RTP packet generators. The model can be used to represent different movies and can be easily adjusted to produce different workloads for simulation studies. We use the SAM generator to compare the performance of three different scheduling methods for video over WiMAX networks: Earliest Deadline First (EDF), Deficit Round Robin (DRR) and a combination of the two. The results show that under overload, EDF introduces unfairness. DRR with deadline is fair and gives the best performance.

Study and Simulation of Video Streaming

In video streaming, quality of service (QoS) guarantee is an important issue. Algorithms used for scheduling play a major role in providing QoS. This paper describes QoS such as loss rate, delay-jitter and throughput in video streaming and their method of evaluation. A simulation environment has been designed combining network simulator, ns2 with video codec to predict the QoS. The scheduling algorithms such as the weighted round robin (WRR ) and deficit round robin (DRR) have been applied and the performance metrics are evaluated and compared.

A novel server selection method to achieve delay-based fairness in the server palm

It is pivotal to achieve delay-based fairness when users access the same content, especially in real-time services, from content-replicated servers based upon the client-server communication model. To resolve this issue, this letter proposes a novel server selection method of providing users with delay-based fairness from all the corresponding servers by applying the delay-based dynamic deficit round robin (D3RR) scheme. The deficit counter of the D3RR is adjusted based upon round trip times (RTTs) of data traffic measured by passive-based probing which ensures low resource waste. Performance evaluation results highlight that the delay variance among all the corresponding servers can be maintained as low as possible and delay-based fairness is guaranteed without unnecessary waste of resources.

Design of Fair Scheduling Schemes for the QoS-Oriented Wireless LAN

How to simultaneously achieve fairness and quality-of-service (QoS) guarantee in QoS-oriented wireless local area networks (LANs) is an important and challenging issue. Targeting at this goal and jointly taking priority setting, fairness, and cross-layer design into account, four scheduling schemes designed for the QoS-oriented wireless LAN mainly based on concepts of deficit count and allowance are proposed in this paper to provide better QoS and fairness. Using multiple deficit count to interframe space (IFS) and allowance to IFS mappings for different priorities, enhanced distributed deficit round robin (EDDRR) and enhanced distributed elastic round robin (EDERR) schemes are designed to reduce (or even eliminate) possible collisions, while EDDRR with backoff interval and EDERR with backoff interval schemes still keep the backoff procedure but dynamically adjust backoff intervals for nonfailure events (the events excluding collisions and failed transmissions) depending on the priority setting and deficit count or allowance with a cross-layer design. Through extensive numerical examples, we show that the proposed schemes outperform the closest scheduling schemes in the literature and exhibit much better QoS as well as station-level and flow-level fairness.

Fair Scheduling for Delay-Sensitive VoIP Traffic

With the wide expansion of voice services over the IP networks (VoIP), the volume of this delay sensitive traffic is steadily growing. The current packet schedulers for IP networks meet the delay constraint of VoIP traffic by simply assigning its packets the highest priority. This technique is acceptable as long as the amount of VoIP traffic is relatively very small compared to other non-voice traffic. With the notable expansion of VoIP applications, however, the current packet schedulers will significantly sacrifice the fairness deserved by the non-voice traffic. In this paper, we extend the conventional Deficit Round-Robin (DRR) scheduler by including a packet classifier, a Token Bucket and a resource reservation scheme and propose an integrated packet scheduler architecture for the growing VoIP traffic. We demonstrate through both theoretical analysis and extensive simulation that the new architecture makes it possible for us to significantly improve the fairness to non-voice traffic while still meeting the tight delay requirement of VoIP applications.

Ordered Round-Robin: An Efficient Sequence Preserving Packet Scheduler

With the advent of powerful network processors (NPs) in the market, many computation-intensive tasks such as routing table look-up, classification, IPSec, and multimedia transcoding can now be accomplished more easily in a router. An NP consists of a number of on-chip processors to carry out packet level parallel processing operations. Ensuring good load balancing among the processors increases throughput. However, such multiprocessing also gives rise to increased out-of-order departure of processed packets. In this paper, we first propose an Ordered Round Robin (ORR) scheme to schedule packets in a heterogeneous network processor assuming that the workload is perfectly divisible. The processed loads from the processors are ordered perfectly. We analyze the throughput and derive expressions for the batch size, scheduling time and maximum number of schedulable processors. To effectively schedule variable length packets in an NP, we propose a Packetized Ordered Round Robin (P-ORR) scheme by applying a combination of deficit round robin (DRR) and surplus round robin (SRR) schemes. We extend the algorithm to handle multiple flows based on a fair scheduling of flows depending on their reservations. Extensive sensitivity results are provided through analysis and simulation to show that the proposed algorithms satisfy both the load balancing and in-order requirements for parallel packet processing.

On the performance anomaly in WiMAX networks

AbstractThe WiMAX system carries a wide range of services in urban and rural environments supporting quality of service. A key element of the QoS framework is the scheduling algorithm adopted by the Base Station (BS). In this paper, we analyze the saturation throughput perceived by Mobile Stations in the cases of two BS scheduling algorithms: Deficit Round Robin (DRR) and time‐based DRR. We demonstrate that the WiFi issue of ‘Performance Anomaly’ also occurs in WiMAX networks: when the BS uses scheduling approaches aimed at achieving throughput‐fairness, like DRR. Performance Anomaly means that when some Mobile Stations (MSs) use a very low bit rate, the throughput of MSs with a high bit rate is dramatically degraded. We propose time‐based DRR as a viable solution to remove the Performance Anomaly. Time‐based DRR is a simple modification of the DRR algorithm that achieves time‐fairness. Its implementation is feasible in WiMAX. The analysis is carried out by means of analytical models supported by NS2 simulations. Two scenarios are considered: the first is suitably set up to highlight and understand the phenomenon of Performance Anomaly; the second examines the impact of Performance Anomaly on a system level focusing on a rural environment. Copyright © 2008 John Wiley & Sons, Ltd.

Vertical dimensioning: A novel DRR implementation for efficient fair queueing

Fair bandwidth allocation is an important mechanism for traffic management in the Internet. Round robin schedulers, such as Deficit Round Robin (DRR), are well-suited for implementing fair queueing in multi-Gbps routers, as they schedule packets in constant time regardless of the total number of active flows. The main drawback of these schemes, however, lies in the maintenance of per flow queues, which complicates the buffer management module and limits the sharing of the buffer space among the competing flows. In this paper, we introduce a novel packet scheduling mechanism, called Vertical Dimensioning (VD) that modifies the original DRR algorithm to operate without per flow queueing. In particular, VD is based on an array of FIFO buffers, whose size is constant and independent of the total number of active flows. Our results, both analytical and experimental, demonstrate that VD exhibits very good fairness and delay properties that are comparable to the ideal Weighted Fair Queueing (WFQ) scheduler. Furthermore, our scheduling algorithm is shown to outperform significantly existing round robin schedulers when the amount of buffering at the router is small.

Fair link striping with FIFO delivery on heterogeneous channels

Link aggregation techniques are often used to achieve higher communication bandwidth by striping network traffic across multiple transmission channels. Due to the variations in bandwidth, latency and loss rate on different channels, link striping suffers from packet reordering thereby adversely affecting the performance of any QoS concerned applications. Hardware-based solutions often prolong transmission latency which is undesirable for delay sensitive applications and are restricted with the available buffer space on the device. Thus, an effective striping protocol that ensures both load balancing and minimal packet reordering is important when striping traffic onto multiple channels. In this paper, we first propose an sequence preserving scheduling (SPS) scheme to schedule packets among multiple heterogeneous communication channels assuming that the workload is perfectly divisible. Packets assigned onto different links for transmission are ordered perfectly by applying divisible load theory (DLT). We analyze the throughput and derive expressions for the batch size, scheduling time and the maximum number of channels that can be supported by the sender and receiver. Further, to effectively schedule variable length packets for link striping, we propose a packetized sequence preserving scheduling (P-SPS) scheme by applying a combined packetized technique of deficit round robin (DRR) and surplus round robin (SRR). Extensive sensitivity results are provided through analysis and simulation to show that the proposed algorithms satisfy both the load balancing and in-order requirements for efficient packet transmission.

Fully decentralized emulation of best-effort and processor sharing queues

Control of large distributed cloud-based services is a challenging problem. The Distributed Rate Limiting (DRL) paradigm was recently proposed as a mechanism for tackling this problem. The heuristic nature of existing DRL solutions makes their behavior unpredictable and analytically untractable. In this paper we treat the DRL problem in a mathematical framework and propose two novel DRL algorithms that exhibit good and predictable performance. The first algorithm Cloud Control with Constant Probabilities (C3P) solves the DRL problem in best effort environments, emulating the behavior of a single best-effort queue in a fully distributed manner. The second problem we approach is the DRL in processor sharing environments. Our algorithm, Distributed Deficit Round Robin (D2R2), parameterized by parameter α, converges to a state that is, at most, O (1/α) away from the exact emulation of centralized processor sharing queue. The convergence and stability properties are fully analyzed for both C3P and D2R2. Analytical results are validated empirically through a number of representative packet level simulations. The closed-form nature of our results allows simple design rules which, together with extremely low communication overhead, makes the presented algorithms practical and easy to deploy.

High-performance packet scheduling to provide relative delay differentiation in future high-speed networks

Due to significant advances in interconnection networks and optical technologies, line rate for future high-speed networks can upgrade to terabits per second (Tb/s). Reduction of computational overhead and decrease of packet queueing delay are two critical issues in the design of a packet scheduler for efficiently delivering relative differentiated services over such high-speed networks. In this paper, we propose a new packet scheduler called multi-level dynamic deficit round-robin (MLDDRR). MLDDRR considers packet size and priority at the same time in making scheduling decision. Thus, MLDDRR can deliver relatively small delays not only for traffic of high priority but also for short packets of each class. Because MLDDRR acts like the shortest job first scheduler, MLDDRR can reduce average queueing delay for each class and also provide a better service for real-time applications with a large amount of short packets. MLDDRR also exploits concurrency and pipelining approach to speedup scheduling decision. Furthermore, MLDDRR can protect the traffic of the highest priority from serious performance degradation due to bursts of low priority traffic or high link utilization, and simultaneously prevent the traffic of the lowest priority from starvation. MLDDRR allows network operators to simply change the level of delay differentiation by adjusting parameters. Complexity analysis and extensive simulation results are presented and illustrate that MLDDRR is a high-performance packet scheduler and suitable for being deployed in future high-speed networks to provide relative delay differentiated service.

Performance analysis of Modified Deficit Round Robin schedulers

Deficit Round Robin (DRR) is a scheduling algorithm which provides fair queuing at O(1) complexity. However, due to its round robin structure, its latency properties are not adequate for latency-cr...

Co-DRR: An Integrated Uplink and Downlink Scheduler for Bandwidth Management over Wireless LANs

Bandwidth management over wired bottleneck links has been an effective way to utilize network resources. For the rapidly emerging IEEE 802.1 1b Wireless LAN (WLAN), the limited WLAN bandwidth becomes a new bottleneck and requires bandwidth management. Most possible existing solutions only exclusively focus on optimizing multimedia traffic, pure downlink or pure uplink fairness, or are incompatible with IEEE 802.1 1b. This study proposes a cooperative deficit round robin (co-DRR), an IEEE 802. lib-compatible host-based fair scheduling algorithm based on the deficit round robin (DRR) and distributed-DRR (DDRR) schemes, to make the uplink and downlink quantum calculations cooperate to simultaneously control uplink and downlink bandwidth. Co-DRR uses the standard PCF mode to utilize the contention-free period to compensate for the unfairness in the contention period. Numerical results demonstrate that: co-DRR can scale up to 100 mobile hosts even under high bit error rate (0.0001) while simultaneously achieving uplink/downlink long-term fairness (CoV<0.01) among competing mobile hosts.

Delivering relative differentiated services in future high-speed networks using hierarchical dynamic deficit round robin

With the increasing deployment of real-time audio/video services over the Internet, provision of quality of service (QoS) has attracted much attention. When the line rate of future networks upgrades to multi-terabits per second, if routers/switches intend to deliver differentiated services through packet scheduling, the reduction of computational overhead and elimination of bottleneck resulting from memory latency will both become important factors. In addition, the decrease of average queueing delay and provision of small delays for short packets are two further critical factors influencing the delivery of better QoS for real-time applications. The advanced waiting time priority (AWTP) is a timestamp-based packet scheduler which is enhanced from the well-known WTP. Although AWTP considers the effect of packet size, the latency resulting from timestamp access and a great quantity of computational overhead may result in bottlenecks for AWTP being deployed over high-speed links. Many existing schedulers have the same problems. We propose a multi-level hierarchical dynamic deficit round-robin (MLHDDRR) scheduling scheme which is enhanced from the existing dynamic deficit round-robin scheduler. The new scheme can resolve these issues and efficiently provide relative differentiated services under a variety of load conditions. Besides, MLHDDRR can also protect the highest priority traffic from significant performance degradation due to bursts of low-priority traffic. We compare the performance of AWTP with the proposed scheme. Extensive simulation results and complexity analysis are presented to illustrate the effectiveness and efficiency of MLHDDRR.

Combining next fit of bin packing with deficit round robin for efficient slot scheduling in Bluetooth

Bluetooth wireless technology is a low power, low cost and short‐range RF technology that permits communication between bluetooth enabled devices, and focuses on replacement of cables between electronic devices. Communication between Bluetooth devices follows a strict master‐slave scheme. Each master device can have up to 7 active slaves and forms a so called piconet. In Bluetooth employing conventional scheduling policies such as Round Robin (RR), POLL or NULL packet is sent when the Master or Slave node does not have any data to send which causes a significant waste of resources. The DRR (Deficit Round Robin) scheduling algorithm can avoid the waste of time and slot of the RR scheduling at the sacrifice of fairness. In this paper we propose an improved DRR (IDRR) scheduling algorithm which effectively combines the DRR and bin packing algorithm. Computer simulation reveals that slot utilization is increased up to about 60% while the total number of used slots is decreased up to about 100%. The proposed IDRR scheduling is thus effective for not only basic data transmission but also real‐time multimedia data transmission.

Self-Configured Fair Queueing

Many core-stateless mechanisms have been proposed to resolve the scalability problem in the core routers. However, they place considerable reliance on the edge routers or anterior core routers to mark correct flow information in corresponding packets. As a result, the condition of incorrect flow information may severely degrade the fairness among different flows. To achieve the robust fairness, an approximately core-stateless fair sharing mechanism, self-configured fair queuing (SCFQ) is proposed in this paper. This mechanism is mainly composed of two rate estimators; one estimator is used to estimate the arrival rate of the malicious flows that can be adopted to emend the incorrect flow information of the arrival packets. The other one is used to estimate the fair share rate. Computer Simulation is applied to compare the fairness of the SCFQ, core-stateless fair queuing (CSFQ), linear fair sharing estimation (LFSE), deficit round robin (DRR), and first in first out (FIFO). From the simulation results, the SCFQ is capable of supporting much better fairness than that of other compared mechanisms under a variety of traffic conditions. Also, the overhead of the SCFQ is low, so it is very suitable to be deployed in high-speed core routers.

MIMO Based Radio Resource Management for UMTS Multicast Broadcast Multimedia Services

MIMO systems promise high performance gains over conventional single antenna systems. To accomplish high data rates over wireless links the use of multiple transmit and receive antennas is an alternative that does not require any extra bandwidth. It has the potential to address the unprecedented demand for wireless services, particularly for the Multimedia Broadcast Multicast Service (MBMS). This service supports downlink streaming and download-and-play type services to large groups of users. From the radio perspective, MBMS includes point-to-point (PtP) and point-to-multipoint (PtM) modes. New proposed MBMS related enhancements in the physical layer specifications and their effects on resource requirements are presented in this paper, such as the use of High Speed Downlink Packet Access (HSDPA) to broadcast/multicast video streaming using the Deficit Round Robin (DRR) scheduler algorithm as a way to maintain an acceptable QoS for all the users. Other improvements, based on the use of MIMO including macro-diversity, are independent of the mode used and are dependent on deployment scenarios, but can yield substantial reduction in resource demand.

Fair sharing using dual service-level agreements to achieve open access in a passive optical network

The Passive Optical Network (PON) is an attractive solution for high-bandwidth access networks. In the context of a broadband access network, the term open access implies the ability of multiple service providers to share the deployed access network infrastructure to make services available to the end users. Multiple services may thereby be delivered over a shared access channel. Open access requires fairness in terms of throughput, delay, jitter, and other network parameters in the access channel among the sharing entities, namely service providers and end users. Since the traffic in an access network is very bursty, an access network may be frequently subjected to high loads for certain durations of time. Meeting the above fairness requirements under such conditions is therefore very challenging. In this study, we first motivate the problem of meeting fairness requirements simultaneously to both service providers and users, which are located at opposite ends of an access channel. We then investigate the importance of two different sets of Service-Level Agreements (SLAs), which we call Dual SLAs. After formulating a mathematical model, we propose an efficient scheduling algorithm to meet Dual SLAs which is based on the well-known concept of max-min fairness. We then demonstrate the effectiveness of our proposed algorithm through simulations using a discrete-event-simulator-based PON set-up, which compares the fairness of the Dual-SLA scheduling algorithm with that of other traditional fair queuing algorithms such as Deficit Round Robin (DRR)

Short-Term QoS Deficit Round Robin: An Efficient Scheduling Scheme for E-PON Systems

In this paper, a design alternative for guaranteeing short-term QoS in the E-PON (Ethernet-Passive Optical Network) OLT (Optical Line Terminal) node is studied. A scheduling algorithm called Short-term QoS Deficit Round Robin (SQ-DRR) is proposed to guarantee tunable deterministic QoS constraints for multimedia applications over E-PON. The major appealing aspect of the scheduler is that it guarantees delay constraint for short-term aggregate burst traffic violating pre-contracted descriptors at the same time without loosing long'-term fairness. We then evaluate the scheduler performance with and without admission control scheme under non-stationary long-range dependence (LRD) traffic. The simulation results indicate that the SQ-DRR performs well in dynamic burst traffic conditions.