Zero-queue ethernet congestion control protocol based on available bandwidth estimation
Introduction
Router's switch fabric is an essential technology that is traditionally addressed using custom Application-Specific Integrated Circuit (ASIC). This ASIC must fulfill particular characteristics including low packet loss, fairness between flows, and low latency (Bachmutsky, 2011). The emergence of very-high-speed serial interfaces and new router's architectures increase the design and manufacturing cost of the switch fabric chipset. Traditionally, switch fabric is manufactured using either shared memory or crossbar switch as shown in Fig. 1a and b respectively. The shared memory architecture requires memory that works times faster than port speed, where is the number of ports which raises scalability issue. On the other hand, crossbar architecture tries to keep the buffering at the edge of the router (Virtual Output Queue VOQ inside line cards). Because this architecture requires VOQs at each ingress port and a central unit (arbiter), it faces scalability issue (Lee, 2014).
In this research, we introduce a new router architecture that uses Ethernet commodity switches as a switch fabric. In this architecture, we keep all buffering at the edge of the router and an Ethernet switch is used as a switch fabric. IEEE has recently presented Data Center Bridging (DCB) (I. 802.1, 2013) that comprises several enhancements to Ethernet network. However, Ethernet network still suffers from HOL blocking, congestion spreading and high latency. To overcome these limitations and achieve a non-blocking switch fabric, we present Ethernet Congestion Control Protocol (ECCP) that maintains Ethernet network non-blocked by preserving switches' queue lengths close to zero leading to minimum latency and no HOL blocking. Unlike traditional Congestion control mechanisms that use packet accumulation in buffers to trigger the rate control process, ECCP estimates available bandwidth and uses this information to control transmission rates before link saturation or data accumulation. Accordingly, it achieves minimum latency by trading off a small margin of link capacity. Therefore, ECCP achieves (i) low queue length, (ii) low latency, and (iii) high throughput, (iv) with no switch modification. Such a mechanism could be used in manufacturing a cost-efficient routers' switch fabric while guaranteeing traditional router characteristics. Besides, it can be utilized as a reliable and robust layer 2 congestion control mechanism for data center applications (e.g. high-performance computing (Snir, 2014), remote direct memory access (RDMA) (Bailey and Talpey), and Fibre Channel over Ethernet (FCoE) (Kale et al., 2011)).
Furthermore, we introduce a mathematical model of ECCP while using the phase plane method. First, we build a fluid-flow model for ECCP to derive the delay differential equations (DDEs) that represent ECCP. Then, we sketch the phase trajectories of the rate increase and rate decrease subsystems. Consequently, we combine these phase trajectories to understand the transition between ECCP's subsystems and to obtain the phase trajectory of the global ECCP system. Subsequently, the stability of ECCP is analyzed based on this phase trajectory. Our analysis reveals that the stability of ECCP depends mainly on the sliding mode motion (Utkin, 1977). Thereafter, we deduce stability conditions that assist in defining proper parameters for ECCP. Besides, several simulations are conducted using OMNEST (Varga and Hornig, 2008) to verify our mathematical analysis. Finally, a Linux-based implementation of ECCP is conducted to verify ECCP's performance through experiment.
The rest of this paper is organized as follows. Related work is introduced in Section 2. Section 3 presents ECCP mechanism. Section 4 introduces the phase plane analysis method in brief. The mathematical model of ECCP is derived in Section 5. The stability analysis of ECCP is deduced in Section 6. Linux-based implementation is presented in Section 7. Finally, Section 8 introduces conclusion and future work.
Section snippets
Related work
In this section, we present some research work that is closely related to congestion control in both Ethernet layer and Transmission Control Protocol (TCP) layer. IEEE has recently presented Data Center Bridging (DCB) (I. 802.1, 2013) that comprise several enhancements for Ethernet network to create a consolidation of I/O connectivity through data centers. DCB aims to eliminate packet loss due to queue overflow. Ethernet PAUSE IEEE 802.3x and Priority-based Flow Control (PFC) (IEEE standard for
ECCP: Ethernet congestion control protocol
In this section, we present ECCP as a distributed congestion prevention algorithm that works on Ethernet layer. ECCP controls data traffic according to the estimate Available Bandwidth () through a network path. ECCP strives to keep link occupancy less than the maximum capacity by a percentage called Availability Threshold (). Traditional congestion control mechanisms aim to keeps the queue around a target level. These mechanisms can reduce queuing latency, but they cannot eliminate it.
Phase plane analysis
In this paper, we use phase plane method to visually represent certain characteristics of the differential equation of the ECCP. Phase plane is used to analyze the behavior of nonlinear systems. The solutions of differential equations are a set of functions which could be plotted graphically in the phase plane as a two-dimensional vector field. Given an autonomous system represented by a differential equation , one can plot the phase trajectory of such a system by following
ECCP modeling
The core element of ECCP is the rate control algorithm. By responding correctly to the calculated feedback, the network load should remain around the target point. For the purpose of simplicity, we made these assumptions:
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All sources are homogeneous, namely they have the same characteristics such as round-trip time.
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Data flows in data center networks have high rates and appear like continuous flow fluid.
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Available bandwidth estimation error is negligible (Measured is used in the simulation to
Stability analysis of ECCP
In this section, phase plane is used in studying the stability of ECCP. Phase plane analysis of ECCP is carried out for the self-increase and rate decrease processes separately. Next, simulation experiments are presented to verify our mathematical analysis.
Linux-based implementation
We have implemented an ECCP testbed using 3 Linux hosts and a 10 Gbps switch. The testbed is connected as shown in Fig. 17 and is configured according to Table 1. In this implementation, we built a Java GUI to periodically collect statistics and plot the actual transmission rate , and cross traffic rate at the receiver (Fig. 20).
In the next section we present several experiments to validate our bandwidth estimation method, and in the following section we present the ECCP testbed implementation.
Conclusion
In this paper, we propose ECCP as a distributed congestion control mechanism that is implemented in line cards or end hosts and does not require any switch modification.
We analyzed ECCP using phase plane method while taking into consideration the propagation delay. Our stability analysis identifies the sufficient conditions for ECCP system stability. In addition, this research shows that the stability of the ECCP system is ensured by the sliding mode motion. However, the stability of ECCP
Acknowledgment
This work is supported by Ericsson Research, the Fonds de Recherche Nature et Technologies (FRQNT) and the Natural Sciences and Engineering Research Council of Canada (NSERC). Sincere gratitude is hereby extended to Brian Alleyne and Andre Beliveau for their help and support in constructing this work.
Mahmoud Bahnasy received the M.Eng. from Université du Québec à Montréal, Canada, in 2014. Currently pursuing the Ph.D. degree in computer science and engineering at École de Technologie Supérieure, Montréal, Canada.
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Mahmoud Bahnasy received the M.Eng. from Université du Québec à Montréal, Canada, in 2014. Currently pursuing the Ph.D. degree in computer science and engineering at École de Technologie Supérieure, Montréal, Canada.
Halima Elbiaze received the Master degree from University of Versailles, France, in 1998, and the Phd from University of Versailles, in March 2002. She is a professor at Université du Québec à Montréal since June 2003. In 2005, Dr. Elbiaze received the Canada Foundation for Innovation Award to build her IP over the DWDM network Laboratory. Her research interests include intelligent optical networks, performance evaluation, traffic engineering, wireless networks, and next generation IP networks. She is the author or coauthor of many journal and conference papers. Her research interests include network performance evaluation, traffic engineering, and quality of service management in optical and wireless networks. She is member of IEEE and OSA.
Bochra Boughzala received her engineering national diploma form INSAT, Tunisia in 2011 and her Master degree in Computer Science from UQAM in 2013. In 2013, she joined Ericsson Research group in Montreal where she now works as experienced researcher in the networking technologies research area. Her research interests include high performance data plane and execution environment, data plane abstractions and domain specific languages, network programmability and software defined networking (SDN), congestion control and traffic management with new interest in 5G Ethernet fronthauling and information centric networking (ICN) for mobile backhaul.