X-Trace: A Pervatsive Network Tracing Framework

This paper takes a different approach to measuring and tracing the performance of the internet than the previous paper. Instead of taking data and analyzing the packets and traces, this paper proposes a more active method of tracing the network. They introduce a framework that inserts tracing metadata within the packets into the network to help trace the network. This framework allows us to trace across layers and protocols, and analyze different causality relationships between the network. This concept is really effective, because it is indeed that a lot of network traffic is caused by a separate flow. For example, a DNS query is often triggered by another HTTP request or email packet. One since website query might lead to queries from ad servers or image servers etc. Thus, an effective way of categorizing network traffic is to take into account these causality relationships.

The framework introduced metadata that is appended to the packets, along with two propagation primitives pushNext and pushDown in order to propagate the metadata along the network. pushDown copies the metadata from one layer to the layer below, and pushNext pushes the metadata to the next hop. Then based on the metadata, you reconstruct the task tree and analyze it. The paper also gives several use cases and applications.

This method of course involves changing the network structure and introducing more traffic in order to trace traffic. Compared to the other method where is was just being a bystander observing the packets pass by. Forgetting about the security implications of the trace, i wonder if it's possible that trace data or mechanisms introduced itself affect the network traffic, thus causing the measured data or analysis to be skewed or inaccurate?