A traffic engineering problem in a network consists of setting up paths between the edge nodes of the network to meet traffic demands while optimizing network performance. It is known that total traffic throughput in a network, or resource utilization, can be maximized if a traffic demand is split over multiple paths. However, the problem formulation and practical algorithms, which calculate the paths and the load-splitting ratios by taking bandwidth, the route constraints or policies into consideration, have not been much touched. In this paper, we formulate the constrained multipath-routing problems with the objective of minimizing the maximum of link utilization, while satisfying bandwidth, the maximum hop count, and the not-preferred node/link list in Linear Programming (LP). Optimal solutions of paths and load-splitting ratios found by an LP solver are shown to be superior to the conventional shortest path algorithm in terms of maximum link utilization, total traffic volume, and number of required paths. Then, we propose a heuristic algorithm with low computational complexity that finds near optimal paths and load-splitting ratios satisfying the given constraints. The proposed algorithm is applied to Multi-Protocol Label Switching (MPLS) that can permit explicit path setup, and it is tested in a fictitious backbone network. The experiment results show that the heuristic algorithm finds near optimal solutions.

We explain how network failures were caused by a natural disaster, describe the restoration steps that were taken, and present lessons learned from the recovery. At 21:26 on December 26th (UTC+9), 2006, there was a serious undersea earthquake off the coast of Taiwan, which measured 7.1 on the Richter scale. This earthquake caused significant damage to submarine cable systems. The resulting fiber cable failures shut down communications in several countries in the Asia Pacific networks. In the first post-earthquake recovery step, BGP routers detoured traffic along redundant backup paths, which provided poor quality connection. Subsequently, operators engineered traffic to improve the quality of recovered communication. To avoid filling narrow-bandwidth links with detoured traffic, the operators had to change the BGP routing policy. Despite the routing-level first aid, a few institutions could not be directly connected to the R&E network community because they had only a single link to the network. For these single-link networks, the commodity link was temporarily used for connectivity. Then, cable connection configurations at the switches were changed to provide high bandwidth and next-generation Internet service. From the whole restoration procedure, we learned that redundant BGP routing information is useful for recovering connectivity but not for providing available bandwidth for the re-routed traffic load and that collaboration between operators is valuable in solving traffic engineering issues such as poor-quality re-routing and lost connections of single-link networks.

The widespread use and increasing popularity of broadband service has prompted a focus on the measurement and analysis of its empirical performance in recent studies. The worldwide view of broadband performance has been examined over the short term with Speedtest.net, but research in this area has not yet provided a long-term evolutionary insight on how DSL, Cable, and Fiber access technologies have influenced on user experience. In this study, we present 6 years of measurement results, from 2006 to 2011, of broadband performance with fast developing broadband networks in Korea. With 57% Fiber penetration in 2011, our data consist of a total of 29M test records and 10M subscribers. Over the 6 years, we have observed a 2.9-fold improvement in download speed (57Mbps), 2.8-fold increase in upload speed (38Mbps), and 0.7-fold decrease in latency due to the high penetration rate of Fiber broadband service and the advanced Cable modem technology. In addition, we carried out longitudinal analysis of various aspects of services, providers, regions, and cost-performance. We believe that the evolutionary Korean broadband measurement results can shed light on how high-speed access technologies are substantially enhancing on end-to-end performance.

Online used markets such as eBay, Yahoo Auction, and Craigslist have been popular due to the web services. Compared to the shopping mall websites like eBay or Yahoo Auction, web community-style used markets often expose the private information of sellers. In Korea, the most popular online used market is a website called “Joonggonara” with more than 13 million users, and it uses an informal posting format that does not protect the users' privacy identifiable information. In this work, we examine the privacy leakage from the online used markets in Korea, and show that 45.9% and 74.0% of sample data expose cellular phone numbers and email addresses, respectively. In addition, we demonstrate that the private information can be maliciously exploited to identify a subscriber of the social network service.