Factors Affecting Performance of Web Flows in Cellular Networks

Studies show that more than 95% of the traffic generated by smartphones typically consists of short-lived TCP flows towards websites. The content of such websites often is distributed across multiple servers which requires clients to resolve multiple DNS names and establish multiple TCP connections to fetch the webpage in its entirety. Studies have shown that network latency in a mobile network (attributed to DNS lookup and TCP connect times) contributes heavily to poor experience when browsing such websites. However, there is little understanding of the factors that contribute to high DNS lookup and TCP connect times. In this paper, we take this further by measuring the Domain Name System (DNS) lookup time and the TCP connect time to popular websites from similar to 25K subscribers of a cellular network operator in Finland. Using a month-long dataset (Oct 2016) of these measurements, we show that LTE offers considerably faster DNS lookup time compared to legacy cellular networks (such as HSPA+ and UMTS). We also show that the model of the device and the proximity of the DNS server to the subscribers impacts the DNS lookup time. Furthermore, the TCP connect time is also affected by the radio technology. We observe that LTE offers a significantly low latency profile such that the TCP connect time to popular websites is reduced by -80% compared to legacy cellular networks. The presence of ISP caches also considerably improves TCP connect times. Using a ping test, we also observe that legacy radio technologies (such as HSPA+ and UMTS) suffer from higher packet loss than LTE.