28,730 research outputs found
Load Balancing a Cluster of Web Servers using Distributed Packet Rewriting
In this paper, we propose and evaluate an implementation of a prototype scalable web server. The prototype consists of a load-balanced cluster of hosts that collectively accept and service TCP connections. The host IP addresses are advertised using the Round Robin DNS technique, allowing any host to receive requests from any client. Once a client attempts to establish a TCP connection with one of the hosts, a decision is made as to whether or not the connection should be redirected to a different host---namely, the host with the lowest number of established connections. We use the low-overhead Distributed Packet Rewriting (DPR) technique to redirect TCP connections. In our prototype, each host keeps information about connections in hash tables and linked lists. Every time a packet arrives, it is examined to see if it has to be redirected or not. Load information is maintained using periodic broadcasts amongst the cluster hosts.National Science Foundation (CCR-9706685); Microsof
A scalable application server on Beowulf clusters : a thesis presented in partial fulfilment of the requirement for the degree of Master of Information Science at Albany, Auckland, Massey University, New Zealand
Application performance and scalability of a large distributed multi-tiered application is a core requirement for most of today's critical business applications. I have investigated the scalability of a J2EE application server using the standard ECperf benchmark application in the Massey Beowulf Clusters namely the Sisters and the Helix. My testing environment consists of Open Source software: The integrated JBoss-Tomcat as the application server and the web server, along with PostgreSQL as the database. My testing programs were run on the clustered application server, which provide replication of the Enterprise Java Bean (EJB) objects. I have completed various centralized and distributed tests using the JBoss Cluster. I concluded that clustering of the application server and web server will effectively increase the performance of the application running on them given sufficient system resources. The application performance will scale to a point where a bottleneck has occurred in the testing system, the bottleneck could be any resources included in the testing environment: the hardware, software, network and the application that is running. Performance tuning for a large-scale J2EE application is a complicated issue, which is related to the resources available. However, by carefully identifying the performance bottleneck in the system with hardware, software, network, operating system and application configuration. I can improve the performance of the J2EE applications running in a Beowulf Cluster. The software bottleneck can be solved by changing the default settings, on the other hand, hardware bottlenecks are harder unless more investment are made to purchase higher speed and capacity hardware
Edge-as-a-Service: Towards Distributed Cloud Architectures
We present an Edge-as-a-Service (EaaS) platform for realising distributed
cloud architectures and integrating the edge of the network in the computing
ecosystem. The EaaS platform is underpinned by (i) a lightweight discovery
protocol that identifies edge nodes and make them publicly accessible in a
computing environment, and (ii) a scalable resource provisioning mechanism for
offloading workloads from the cloud on to the edge for servicing multiple user
requests. We validate the feasibility of EaaS on an online game use-case to
highlight the improvement in the QoS of the application hosted on our
cloud-edge platform. On this platform we demonstrate (i) low overheads of less
than 6%, (ii) reduced data traffic to the cloud by up to 95% and (iii)
minimised application latency between 40%-60%.Comment: 10 pages; presented at the EdgeComp Symposium 2017; will appear in
Proceedings of the International Conference on Parallel Computing, 201
Automated Dynamic Firmware Analysis at Scale: A Case Study on Embedded Web Interfaces
Embedded devices are becoming more widespread, interconnected, and
web-enabled than ever. However, recent studies showed that these devices are
far from being secure. Moreover, many embedded systems rely on web interfaces
for user interaction or administration. Unfortunately, web security is known to
be difficult, and therefore the web interfaces of embedded systems represent a
considerable attack surface.
In this paper, we present the first fully automated framework that applies
dynamic firmware analysis techniques to achieve, in a scalable manner,
automated vulnerability discovery within embedded firmware images. We apply our
framework to study the security of embedded web interfaces running in
Commercial Off-The-Shelf (COTS) embedded devices, such as routers, DSL/cable
modems, VoIP phones, IP/CCTV cameras. We introduce a methodology and implement
a scalable framework for discovery of vulnerabilities in embedded web
interfaces regardless of the vendor, device, or architecture. To achieve this
goal, our framework performs full system emulation to achieve the execution of
firmware images in a software-only environment, i.e., without involving any
physical embedded devices. Then, we analyze the web interfaces within the
firmware using both static and dynamic tools. We also present some interesting
case-studies, and discuss the main challenges associated with the dynamic
analysis of firmware images and their web interfaces and network services. The
observations we make in this paper shed light on an important aspect of
embedded devices which was not previously studied at a large scale.
We validate our framework by testing it on 1925 firmware images from 54
different vendors. We discover important vulnerabilities in 185 firmware
images, affecting nearly a quarter of vendors in our dataset. These
experimental results demonstrate the effectiveness of our approach
A Massively Scalable Architecture For Instant Messaging & Presence
This paper analyzes the scalability of Instant Messaging & Presence (IM&P) architectures. We take a queueing-based modelling and analysis approach to find the bottlenecks of the current IM&P architecture at the Dutch social network Hyves, as well as of alternative architectures. We use the Hierarchical Evaluation Tool (HIT) to create and analyse models analytically. Based on these results, we recommend a new architecture that provides better scalability than the current one. \u
ClouNS - A Cloud-native Application Reference Model for Enterprise Architects
The capability to operate cloud-native applications can generate enormous
business growth and value. But enterprise architects should be aware that
cloud-native applications are vulnerable to vendor lock-in. We investigated
cloud-native application design principles, public cloud service providers, and
industrial cloud standards. All results indicate that most cloud service
categories seem to foster vendor lock-in situations which might be especially
problematic for enterprise architectures. This might sound disillusioning at
first. However, we present a reference model for cloud-native applications that
relies only on a small subset of well standardized IaaS services. The reference
model can be used for codifying cloud technologies. It can guide technology
identification, classification, adoption, research and development processes
for cloud-native application and for vendor lock-in aware enterprise
architecture engineering methodologies
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