Wei Liang

Northeast Institute of Geography and Agroecology, Beijing, Beijing Shi, China

Are you Wei Liang?

Claim your profile

Publications (9)0 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Highly virtualized data center have placed many new and unique requirements on the networking fabric. Conventional network protocols limit the scale, latency, throughput of cloud networks. To solve these problems, the large layer 2 technology is proposed. The large layer 2 technology such as TRILL and SPB has obvious advantages in scalability, convergence and resource utilization compared with the traditional layer 2 technology. However, the disadvantages of employing the large layer 2 technology are barely addressed. To study the overhead of large layer 2 networking, we setup a data center environment with 6 core switches and conduct experiments to compare the performance of the representative large layer 2 protocol-TRILL and the typical layer 2 technology-STP. We also evaluate the intra-VLAN forwarding and inter-VLAN forwarding of TRILL. From our experiments, it is observed that the forwarding efficiency of TRILL is 30.16% lower than STP on average. It is also observed that the inter-VLAN traffic forwarding of TRILL averagely costs about 54% more time and consumes about 5% more CPU than intra-VLAN with a fixed packet generation rate. This is the first study towards unveiling the inefficiency of large layer 2 approach in data center networks as far as we know.
    Innovative Computing Technology (INTECH), 2013 Third International Conference on; 01/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: It is common that many enterprises tend to operate several datacenters applying virtualization technologies from different vendors. However, for virtual machine migration across different vendors, currently there is no feasible method to transfer the corresponding network policies as well. In this paper, we show a cross-vendor network policy adaptor (CVNPA), which is able to cooperate with today's cloud computing platforms and to provide seamless network policy migration across virtual switches from different vendors. We experiment CVNPA in our simulated cloud computing environment with OpenStack as their cloud computing platform. The results show that CVNPA can transfer corresponding network policy over heterogeneous virtual switches efficiently and automatically during the process of VM migration with little overhead.
    Distributed Computing Systems Workshops (ICDCSW), 2013 IEEE 33rd International Conference on; 01/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: In recent years, virtualization technologies are applied to data centers for resource sharing. Virtual Machine Monitor (VMM) can consolidate virtual machines (VMs) running on multiple physical servers onto a single one via live VM migration, consequently improving energy efficiency of data centers. VM consolidation is usually modeled as a bin packing problem aiming at minimizing the number of servers being used. However, resource consumption overhead of consolidating VMs is seldom considered in existing approaches. In this paper, the overhead is defined as the resource consumption difference between the server and all the VMs running on it. We theoretically and experimentally prove that under the realistic constrains, this overhead exists and remains steady with the increasing of consolidating VMs. We also propose Margin Reserved Consolidation (MRC) algorithm to supplement existing works. Besides, we conduct experiments to validate the overhead. Experiments based on a representative benchmark show that 11.7% of the server's CPU resource is occupied by the overhead averagely.
    Global Communications Conference (GLOBECOM), 2012 IEEE; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: Encoding topology information into logical addresses is a new trend in data center network (DCN) as it can help to improve the scalability and routing efficiency. Regretfully, to configure large-scale data center manually is not only time-consuming but also error-prone. Because of this, research in auto-configuration becomes getting more attention. Previous works in auto-configuration generally neglect the properties of given topology and cause high computational complexity. In this paper, we propose a new auto-configuration algorithm called Pivot-based Fast Automatic Configuration (PFAC). Leveraging properties of the given data center network topology, PFAC can assign addresses to physical devices in the data center automatically and efficiently. The experiments show that the processing time of PFAC is reduced by about 30% compared to previous works.
    Cloud Networking (CLOUDNET), 2012 IEEE 1st International Conference on; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: Towards Inferring Inter-Domain Routing Policies in ISP Networks
    IEICE Transactions. 01/2011; 94-B:3049-3056.
  • [Show abstract] [Hide abstract]
    ABSTRACT: BGP dictates routing between autonomous systems with rich policy mechanisms in today's Internet. Operators translate high-level policy objectives into low-level router configurations without a comprehensive understanding of the actual effects on the network behavior, leaving the routing management an error-prone and time-consuming procedure. A fundamental question is: how to verify the intended routing principles against the actual routing effects of an ISP? In this paper, we develop a Routing Policy Inference Model (RPIM) as the first step towards addressing this fundamental issue. RPIM extracts various policy patterns from the BGP routing tables and translates them into high-level policy objectives of the ISP using a grouping and matching technique. Our work bridges the gap between the high-level policy objectives and the actual routing effects, which provides network operators with a novel approach to verify their policy design principles, thus facilitating the routing management. We evaluate our approach by extensive simulations using the Internet AS-level topology from CAIDA and the real routing data from the Abilene network. Simulation results show that RPIM achieves over 78.94% average inference accuracy in our suggested optimal threshold range. We also verify RPIM on several operating ISPs by the registered policies in an Internet Routing Registry (IRR). A representative case study on AS3292 demonstrates that RPIM effectively infers high-level policy objectives from routing data.
    Proceedings of the Global Communications Conference, GLOBECOM 2011, 5-9 December 2011, Houston, Texas, USA; 01/2011
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Despite the recent and remarkable popularity of P2P IPTV systems, the study of their characteristics on largescale broadcasting is rare. In this paper, we have undertaken a measurement study on one of the most popular P2P IPTV systems, PPStream, during the 29th Olympics broadcasting. We deployed our dedicated measurement tool, PPS-Sniffer, under different network environments, and collected extensive data during a large number of events. We evaluate the playback delay, and the peering strategies towards local cluster. We also investigate the data scheduling, and its impact on the playback quality and the control overhead. To the best of our knowledge, results obtained in our study are unique and new as compared with existing work. Specifically, our study demonstrates that: (1) The playback delay is notable in Olympic channels, even for close peers. (2) Peering strategies of PPStream target mainly on the ISP level, and should exploit peers of local clusters to reduce the playback lag among close peers. (3) We unveil an overhead-quality tradeoff that sheds light on the design of future systems that can achieve a good balance. Our study aids the understanding of significant performance and design issues of PPStream, and is also useful for optimizing, modeling and the future design of P2P IPTV systems.
    Global Telecommunications Conference, 2009. GLOBECOM 2009. IEEE; 01/2010
  • [Show abstract] [Hide abstract]
    ABSTRACT: P2P streaming technique is spreading widely and the study of its characteristics on large-scale broadcasting is meaningful and important. In this paper, we have undertaken a measurement on one of the most popular P2P IPTV systems, PPStream, during the 29<sup>th</sup> Beijing Olympics. We collected extensive data traces under different network environments. New and unique observations are presented in our study as compared with existing measurements. Specifically, our results show that 1.) The playback delay is more remarkable in Olympics channels; 2.) Parent overlap is extremely small even for peers very nearby; 3.) The change of buffering fluctuates periodically in both Olympic and ordinary channels; 4.) Smaller scheduling unit is employed in Olympic channels with potential inefficiency. Measurement results obtained in our study bring to light significant performance and design issues of P2P live streaming systems during large-scale broadcasting, and are valuable in better understanding, optimizing and modeling of such systems.
    Computers and Communications, 2009. ISCC 2009. IEEE Symposium on; 08/2009
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Border gateway protocol (BGP) is the de facto inter-domain routing protocol nowadays, and its behavior greatly impacts the end-to-end Internet performance. Various work has been done on revealing the cause and location of BGP routing instability, and they are helpful for operators to recover their networks from routing disasters. However, current approaches have the "magic numbers" problem in choosing the parameters, which prevents the accuracy in finding the correct location from rising above a certain level. In this paper, we present a statistical approach based on pattern matching to accurately identify familiar BGP routing instabilities and pinpoint their locations. Simulation results show that our approach can achieve over 80% locating precision if the ongoing instability is not well isolated, and increases the average locating precision from 60% to 75% for a BGP session availability event.
    Proceedings of the Global Communications Conference, 2008. GLOBECOM 2008, New Orleans, LA, USA, 30 November - 4 December 2008; 01/2008