AT&T Labs Research — Leading Invention, Driving Innovation

The definitive version was published in ITC 2011. , 2011-09-06, http://i-teletraffic.org/fileadmin/ITC23_files/Copyright_form_ITC2011.pdf

{The volume of Internet traffic over 3G wireless networks is sharply rising. In contrast to many Internet services utilizing replicated resources (e.g., content distribution networks), the current 3G standard architecture employs hierarchical routing, where all user data traffic goes through a small number of aggregation points using logical tunnels. In this paper, we investigate the potential system inefficiency and performance issues due to the interplay of the two systems. We first identify a number of aspects affecting system inefficiency and service performance and then quantify the impact by analyzing trace data obtained from a large-scale 3G network and a CDN provider. We find that extra packet headers used for hierarchical routing result in significant byte overhead (around 6\%). We also find that the detour due to hierarchical routing can cause a packet to travel extra distance by up to 1627km on the average case, which based on our data analysis, corresponds to around 45.4\% increase in round-trip latency. Furthermore, we identify a pathological case due to DNS caching when a mobile device switches between wireless technologies. In our measurement study on the Internet, we find that this issue can cause up to an order of magnitude throughput degradation (0.9Mbps vs. 10.8Mbps). We also study how to achieve performance improvement by deploying system resources more strategically.}

(c) ACM, 2010. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM CoNext 2010 , 2010-12-01

IPTV service providers offering Video-on-Demand (VoD) typically have many servers at each metropolitan office to store all the videos in the library. With the rapid increase in the VoD library size, it will soon become infeasible to replicate the entire library at each office. We present an approach for intelligent content placement that scales to large VoD library sizes (e.g., 100Ks of videos). We formulate the problem as a mixed integer program (MIP) that takes into account constraints such as disk space, link bandwidth, and the skew in content popularity. To overcome the challenges of scale, we employ a Lagrangian relaxation-based decomposition technique that can find a near-optimal solution (e.g., within 1-2%) with orders of magnitude speedup, relative to solving even the LP relaxation via standard software. We also present simple strategies to address practical issues such as popularity estimation, content updates, short-term popularity fluctuation, and frequency of placement updates. Using traces from an operational system, we show that our approach significantly outperforms simpler placement strategies. For instance, our MIP-based solution can serve all requests using only half the link bandwidth used by LRU cache replacement policy. We also investigate the trade-off between disk space and network bandwidth.