Browsing by Author "Hwang, Ren-Hung"

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In-Lab Replay Testing under Real Traffic with a Case Study on WLAN Routers
(2017-03-01)
Lin, Ying-Dar
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Hwang, Ren-Hung
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Lu, Chun-Nan
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Hung, Jui-Tsun
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資訊工程學系
Replaying artificial or real-world traffic is a method used to test networking devices. Using real-world traffic is desirable as it uncovers more realistic properties such as traffic diversity and complicated user behaviors. In this paper, we propose an in-lab replay testing (ILRT) framework, composed of a monitor, a traffic replayer and a library of real-world traffic traces, to replay captured packet traces to test networking devices. To demonstrate its effectiveness, a total of 28 WLAN routers were tested to evaluate whether they could work stably for an extended time. In our experiments, 53.57% and 100% of devices under test (DUTs) were triggered critical (L1) failures and tolerable (L2) failures, respectively. 21.43% and 100% of DUTs were triggered more than one L 1 and L2 failures, respectively. Among high-spec DUTs, there was 25% of DUTs which were triggered L1 failures. Furthermore, among 458 test results, chance of pass, L1 failure, and L2 failure is 2.84%, 7.86%, and 89.3%, respectively. The results showed that even though these devices have passed traditional lab tests, there is still a good chance for them to fail under real-world traffic.
Integration of Spatial Reuse and Allocation for Downlink Broadcast in LTE-Advanced and WiMAX Relay Networks
(2015-11-01)
Lin, Cheng-Hsien
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Hwang, Ren-Hung
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Wu, Jang-Jiin
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Lee, Jeng-Farn
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Lin, Ying-Dar
Downlink broadcast in LTE-Advanced-(LTE-A) and WiMAX-based relay networks is a crucial service for multimedia delivery. Currently, most research effort goes into devising efficient resource allocation mechanisms to achieve more efficient resource utilization. However, spatial reuse, which is an important technique in improving transmission capacity, has received little attention in the literature. Thus, in this work, we investigate ways of achieving more efficient resource allocation in wireless relay networks via spatial reuse. We first formulate a joint spatial reuse and resource allocation problem as an integer linear programming (ILP) model. We then consider a grouping mechanism in which relay stations (RSs) are grouped together if they do not interfere with each other\'s transmission signal. RSs in the same group can thus utilize spatial reuse by using the same set of resources to broadcast data. Because of the high computational complexity of the ILP model, we propose a two-phase heuristic solution. In the first phase, the enhanced-resource diminishing principle approach is employed to determine the number of resources required by the base station and a set of selected RSs. In the second phase, a max-coloring algorithm is employed to organize the selected RSs into broadcast groups and then assign the required resources to each group by exploring the maximum advantage of spatial reuse. The simulation results show that the proposed solution improves system performance up to 61%, as compared with two existing mechanisms.
On Campus IPv6 Beta Site: Requirements, Solutions, and Product Defect Evaluation
(2015-12-01)
Lin, Ying-Dar
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Hwang, Ren-Hung
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Kulkarni, Raghavendra
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Tseng, Chinyang Henry
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Hsu, Chun-Hung
Due to IPv4 address exhaustion, IPv6 deployment has been in progress and the transition from IPv4 to IPv6 has become more imminent. In this article, we report an on-campus IPv6 beta site coexisting with IPv4 networks and designed with requirements from its stakeholders. We conducted a wide range of test cases, from essential functionality tests to advanced stability tests which require complex interoperability tests and cannot be performed in laboratory testing. After one year of operation, tens of defects were observed and seven representative defects in dual-stack tunneling, IPv6 routing table, RIPng, and OSPFv3, are reported. Most defects are reproducible, and some could be fixed by proper configuration while others are caused by flaws in system design, memory management, or protocol implementation. We suggest careful configuration, overloading prevention, limited resource sharing, and robust error handling as the lessons to vendors and administrators of IPv6 devices.
On Campus IPv6 Beta Site: Requirements, Solutions, and Product Defect Evaluation
(2015-12)
Lin, Ying-Dar
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Hwang, Ren-Hung
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Kulkarni, Raghavendra
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Tseng, Chinyang Henry
;
Hsu, Chun-Hung
Due to IPv4 address exhaustion, IPv6 deployment has been in progress and the transition from IPv4 to IPv6 has become more imminent. In this article, we report an on-campus IPv6 beta site coexisting with IPv4 networks and designed with requirements from its stakeholders. We conducted a wide range of test cases, from essential functionality tests to advanced stability tests which require complex interoperability tests and cannot be performed in laboratory testing. After one year of operation, tens of defects were observed and seven representative defects in dual-stack tunneling, IPv6 routing table, RIPng, and OSPFv3, are reported. Most defects are reproducible, and some could be fixed by proper configuration while others are caused by flaws in system design, memory management, or protocol implementation. We suggest careful configuration, overloading prevention, limited resource sharing, and robust error handling as the lessons to vendors and administrators of IPv6 devices.
Open Source for Networking: Protocol Stacks
(2014-03-01)
Lin, Ying-Dar
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Hwang, Ren-Hung
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Armitage, Grenville
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Eramo, Vincenzo
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交大名義發表
Open Source for Networking: Protocol Stacks
(2014-03-01)
Lin, Ying-Dar
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Hwang, Ren-Hung
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Armitage, Grenville
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Eramo, Vincenzo
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交大名義發表
Open Source for Networking: Tools and Applications
(2014-09-01)
Lin, Ying-Dar
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Hwang, Ren-Hung
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Armitage, Grenville
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Eramo, Vincenzo
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交大名義發表
Toward Optimal Resource Allocation of Virtualized Network Functions for Hierarchical Datacenters
(2018-12-01)
Wang, Chih-Chiang
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Lin, Ying-Dar
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Wu, Jang-Jiin
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Lin, Po-Ching
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Hwang, Ren-Hung
Telecommunications service providers (TSPs) previously provided network functions to end users with dedicated hardware, but they are resorting to virtualized infrastructure for reducing costs and increasing flexibility in resource allocation. A representative case is the Central Office Re-architected as Datacenter (CORD) project from AT&T, which aims to deploy virtualized network functions (VNFs) to over 4000 central offices (COs) across the U.S. However, there is a wide spectrum of options for deploying VNFs over the COs, varying from highly distributed to highly centralized manners. The former benefits end users with short response time but has its inherent limitation on utilizing geographically dispersed resources, while the latter allows resources to be better utilized at a cost of longer response time. In this work, we model the TSP's virtualized infrastructure as hierarchical datacenters, namely hierarchical CORD, and provide a resource allocation solution to strike the optimal balance between the two extreme options. Our evaluations reveal that in general, the 3-tier architecture incurs the least cost in case of deploying VNFs under moderate or loose delay constraints. Furthermore, the margin of improvement on the resource allocation cost increases inversely with the overall system utilization rate. Our results also suggest that as heavy request load overwhelms the network infrastructure, the relevant VNFs shall be migrated to lower-tier edge datacenters or to some nearby datacenters with superior network capacity. The evaluations also demonstrate that the proposed model allows highly adaptive VNF deployment in the hierarchical architecture under various conditions.