Chao-Chih Chen

RED-BL: Energy solution for loading data centers

Cloud infrastructure providers and data center operators spend a major portion of their operations budget on the electric bills. We present RED-BL (Relocate Energy Demand to Better Locations), a framework for determining an optimal mapping of workload to an existing set of data centers while considering the cost of workload relocation. Within each workload mapping interval, RED-BL solution exploits the geo diversity in electricity price markets. The temporal diversity in those markets is simultaneously exploited by considering a planning window comprising several mapping intervals. Using workload traces from live Internet applications and electricity prices from the US markets, RED-BL can reduce the electric bill by as much as 81% from the case when the workload is equally distributed. Compared to a single data center deployment, an average reduction of 27% in electric bill can be achieved when RED-BL uses 10 or more data centers, a common case for most operators. When compared to existing workload relocation solutions, RED-BL achieves a further reduction of 13.63%, on average. While modest, this reduction can save millions of dollars for the operators. The cost of this saving is an inexpensive computation at the start of each planning window.

Routing-as-a-Service (RaaS): A framework For tenant-directed route control in data center

In a multi-tenant data center environment, the current paradigm for route control customization involves a labor-intensive ticketing process, in which tenants submit route control requests to the landlord. This results in a tight coupling between tenants and landlord, extensive human resource deployment, and long ticket resolution time. We propose Routing-as-a-Service (RaaS), a framework for tenant-directed route control in data centers. We show that RaaS-based implementation provides a route control platform for multiple tenants to perform route control independently with little administrative involvement, and for the landlord to set the overall network policies. RaaS-based solutions can run on commercial off-the-shelf (COTS) hardware and leverage existing technologies, so it can be implemented in existing networks without major infrastructural overhaul. We present the design of RaaS, introduce its components, and evaluate a prototype based on RaaS.

Experimental Study of Measurement-based Admission Control for Wireless Mesh Networks

The increased deployment of wireless mesh networks (WMNs) should be complemented by a robust resource management scheme that can provide performance guarantees to mission-critical applications. Several admission control schemes have been presented for wireless LANs and wireless ad-hoc networks. However, wireless mesh networks, with static wireless back-bone and multi-hop communication, pose new design challenges. Evaluation of existing admission control schemes has been done primarily via simulations, which often do not have accurate models for capturing interference between adjacent wireless links and nodes. In this paper, we develop light-weight monitoring modules to measure current network/traffic conditions and estimate end-to-end path delay, which is then incorporated in our admission control decision. We utilize a novel layer-2 packet forwarding mechanism, based on the wireless distribution system (WDS) for WMNs. We evaluate our scheme via experiments conducted on a test-bed consisting of IEEE 802.11a-based nodes that form a wireless mesh. Results show that our proposed scheme can provide performance assurance without incurring too much control overhead.

Routing-as-a-service (RaaS): a framework for tenant-directed route control in data center

In a multi-tenant data center environment, the current paradigm for route control customization involves a labor-intensive ticketing process, in which tenants submit route control requests to the landlord. This results in a tight coupling between tenants and landlord, extensive human resource deployment, and long ticket resolution time. We propose Routing-as-a-Service (RaaS), a framework for tenant-directed route control in data centers. We show that RaaS-based implementation provides a route control platform for multiple tenants to perform route control independently with little administrative involvement, and for the landlord to set the overall network policies. RaaS-based solutions can run on commercial off-the-shelf (COTS) hardware and leverage existing technologies, so it can be implemented in existing networks without major infrastructural overhaul. We present the design of RaaS, introduce its components, and evaluate a prototype based on RaaS.

A Proxy View of Quality of Domain Name Service, Poisoning Attacks and Survival Strategies

The domain name system (DNS) provides a critical service for the Internet -mapping of user-friendly domain names to their respective IP addresses. Yet, there is no standard set of metrics quantifying the quality of domain name service or QoDNS, let alone a thorough evaluation of it. This paper attempts to fill this gap from the perspective of a DNS proxy/cache, which is the bridge between clients and authoritative servers. We present an analytical model of DNS proxy operations that offers insights into the design tradeoffs of DNS infrastructure and the selection of critical DNS parameters. After validating our model against simulation results, we extend it to study the impact of DNS cache poisoning attacks and evaluate various DNS proposals with respect to the QoDNS metrics. In particular, we compare the performance of two newly proposed DNS security solutions: one based on cryptography and one using collaborative overlays.

Quality of name resolution in the Domain Name System

The Domain Name System (DNS) is integral to todays Internet. Name resolution for a domain is often dependent on servers well outside the control of the domains owner. In this paper we propose a formal model for analyzing the name dependencies inherent in DNS, based on protocol specification and actual implementations. We derive metrics to quantify the extent to which domain names affect other domain names. It is found that under certain conditions, the name resolution for over one-half of the queries exhibits influence of domains not expressly configured by administrators. This result serves to quantify the degree of vulnerability of DNS due to dependencies that administrators are unaware of. The model presented in the paper also shows that the set of domains whose resolution affects a given domain name is much smaller than previously thought. The model also shows that with caching of NS target addresses, the number of influential domains expands greatly, thereby making the DNS infrastructure more vulnerable.

SWIM: A Switch Manager for Datacenter Networks

Datacenter networks are rapidly increasing the number of servers they support, making equipment management highly complex. Network attributes are scattered among network engineering groups, making troubleshooting cumbersome. Meanwhile, network vendor diversity leads to an explosion of vendor-specific management systems or single-use automation scripts, limiting network scalability and increasing management time and effort. Switch Manager (SWIM) copes with this growth by standardizing the language for describing network attributes and unifying the interface for executing management actions on the network equipment.

RED-BL: Evaluating dynamic workload relocation for data center networks

Abstract In this paper, we present RED-BL (Relocate Energy Demand to Better Locations), a framework to minimize the electricity cost for operating data center networks over consecutive intervals of fixed duration. Within each interval, RED-BL provides a mapping of workload to a set of geographically distributed data centers. To this end, RED-BL uses the geographical and temporal variations in electricity prices as exhibited by electrical energy markets. In addition, we incorporate the transition costs associated with a change in workload mapping from one interval to the next, over a planning window comprising multiple such intervals. This results in a sequence of workload mappings that is optimal over the entire planning window, even though the workload mapping in a given interval may not be locally optimal. Our evaluation of RED-BL uses electricity prices from the US markets and workload traces from live Internet applications with millions of users. We find that RED-BL can reduce the electric bill by as much as 45% compared to the case when the workload is uniformly distributed. When compared to existing workload relocation solutions, for a wide range of data center deployment sizes, RED-BL achieves electricity cost savings that are 8.28% higher, on average. This seemingly modest reduction can save millions of dollars for the operators. The cost of this saving is an inexpensive computation at the start of each planning window.

Experimental Evaluation of the Impact of Packet Capturing Tools for Web Services

Network measurement is a discipline that provides the techniques to collect data that are fundamental to many branches of computer science. While many capturing tools and comparisons have made available in the literature and elsewhere, the impact of these packet capturing tools on existing processes have not been thoroughly studied. While not a concern for collection methods in which dedicated servers are used, many usage scenarios of packet capturing now requires the packet capturing tool to run concurrently with operational processes. In this paper we perform experimental evaluations of the performance impact that packet capturing process have on webbased services; in particular, we observe the impact on web servers. We find that packet capturing processes indeed impact the performance of web servers, but on a multi- core system the impact varies depending on whether the packet capturing and web hosting processes are co-located or not. In addition, the architecture and behavior of the web server and process scheduling is coupled with the behavior of the packet capturing process, which in turn also affect the web servers performance.