Configuring DHCP Leases in the Smartphone Era

摘要

The Dynamic Host Configuration Protocol (DHCP) was introduced nearly 20 years ago as a mechanism for hosts to automatically acquire IP addresses. While the protocol remains the same, its usage has evolved, especially in the last decade with the introduction of mobile devices and wireless local area networks. In this paper we investigate the impact that new types of wireless devices, such as smart-phones, have on DHCP. We use two one-month long traces, collected at a corporate and an educational network, and we compare side-by-side DHCP usage patterns. We develop a novel passive fingerprinting technique based on DHCP messages to determine the device type and operating system. We show that DHCP implementations vary among device types and have an effect on DHCP lease durations. To improve network address utilization, without introducing any protocol changes, we propose a new leasing strategy which takes into account device types. This strategy, compared to current approaches, improves the address utilization without considerably increasing the DHCP overhead.