X-Trace: A Pervasive Network Tracing Framework

Summary:

X-trace is a tracing framework which goes beyond the single application/protocol/layer/administration limitations of other tracing frameworks such as tracerout. X-trace works by user inserting an X-trace meta data along the request into the system and further logging by every layer/level (which is X-traced enabled) when they see the metadata.

A key component of X-trace is the generation of a task tree which includes all the elements involved in the task also capturing the direction of causality in every relationship. The task tree is constructed from the reports received from the network elements. There are certain concerns in terms of administrative regions being unwilling to share certain information which is solved by aggregating the reports within each region and letting the administrative entities decide on the level of exposure to external users.

The authors give two implementation examples, one a web hosting site and second an overlay network (based on I3 and Chord) which give strong indications of usability and effectiveness of X-trace framework. The paper also has a nice discussion section which discusses the potential draw-back and show stoppers. Security is again a main concern since users of distinct administrative boundary can initiate possibly heavy report generations. Filtering malicious users might potentially alleviate this problem but it is hard to predict the effects of potential attacks until the system is widely deployed. Some other areas which would require more investigation as indicated by authors are non-tree request structure, partial deployments, report loss and managing report traffic.

Critique:

To me X-trace sounds like a neat idea since the trace traverses exactly along the data. Nevertheless it still seems to require a lot of modifications at many different levels and at a very large scale if it aiming to enable a complete visibility. I would think that at more limited scales X-trace can be adapted much faster.

The overall paper was written well. As evaluating this system at larger scale seems to need much more work the authors were only able to demonstrate certain case studies which seems to be a reasonable approach for this problem. In overall an interesting paper, but I personally think there are quite a few more interesting papers (of different subject such as wireless) that we could have read instead.