3G Meets the Internet: Understanding the performance of hierarchical routing in 3G networks

The volume of Internet traffic over 3G wireless networks is sharply rising. In contrast to many Internet services utilizing replicated resources, such as Content Distribution Networks (CDN), 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 study the performance implications of the interplay when 3G users access Internet services. We first identify a number of scenarios in which 3G users' service performance can be affected under hierarchical routing in comparison to an idealized flat routing. We then quantify this service impact by analyzing trace data obtained from a large-scale 3G network and a CDN provider. We find that the performance difference between hierarchical routing and flat routing increases when a 3G user accesses highly replicated service, and can further aggravates when the DNS caching is not properly managed under vertical handoff. For example, in our data analysis, the detour under hierarchical routing can cause a packet to travel extra distance by up to 1627km on the average case, which can lead to around 45.4% increase in round-trip latency. We also perform a measurement study to demonstrate that user mobility and web applications can lead to unexpected performance-impacting interactions, which can degrade the download throughput by up to an order of magnitude (0.9Mbps vs. 10.8Mbps).