Using synthetic packet pairs to investigate real-time latency variations over home broadband connections

Synthetic Packet Pairs (SPP) is a smart approach to estimating round trip time (RTT) with passive monitoring. SPP gives greater accuracy and resolution than conventional active methods. With the ability to measure RTT as experienced by a particular application, SPP can be used to visualise the effectiveness of QoS implementations and further understand delay characteristics of specific traffic. Additionally, monitoring traffic with SPP can reveal properties of the underlying protocol stack and link configuration. In this report we employ CAIA’s free implementation of SPP to examine the network delay experienced by a few applications, as well as to demonstrate queueing and serialisation delay as displayed in a typical ADSL home broadband connection.