Chris, thanks for mentioning me/our project! Rolf, thanks for pointing to our recent 2nd reverse traceroute paper!

Our recent paper addressed what we saw as the major limitations of my original 1st reverse traceroute paper that Chris linked (accuracy and scalability). We intend our system to be an open tool for the community, and we are currently testing it with outside users. It can potentially measure paths to you from any responsive host on the Internet, without requiring access/changes/new support at the host or routers along the path (more details below). If you want to try out our tool during this testing phase, please email us at revtr@ccs.neu.edu 

I'll describe our project a bit, including some of the similarities and differences between our project and Rolf's. I'll call ours revtr-2.0, since that's what we call it in the paper, and I'll call Rolf's revtr-lg, since it is somewhat akin to a Looking Glass server.

The goal in both is the same: the user u wants to measure the path (IP addresses of routers, RTTs per hop) from a remote host h to u, without direct control of h. 

revtr-2.0's approach relies on the rarely used (but actually widely supported) IP Record Route option, coupled with some measurement tricks. In my understanding, revtr-lg proposes to add a new ICMP type.

Both approaches rely on a set of distributed vantage points running an implementation of their particular reverse traceroute code, but the way they use the vantage points is very different, and that leads to the main differences between the approaches. Our current tool has vantage points at 150 sites around the world, so I'll use that number as an example for discussion.

COVERAGE

- revtr-lg allows a user u to contact a vantage point to request a traceroute from the vantage point to u, so it measures from sites that have opted to run the revtr-lg software. So, with 150 sites, revtr-lg would be able to measure 150 paths to u.

- revtr-2.0 uses the vantage points to issue various measurements that combine to measure the route to u from any host h the user requests -- h need not be part of the system and need not run any special software. We were able to use revtr-2.0 and its 150 vantage points to measure paths from hosts in 39,544 ASes. (According to APNIC estimates, these ASes host 92.6% of Internet users). 

- If you want to use revtr-2.0 to measure paths to you (from whichever hosts you request), you need to run our client code on a public IP address. It will contact our system and use our vantage points to measure routes to you. If you want to try out our tool, please email us at revtr@ccs.neu.edu 

- Our vantage points currently support running a few tens of millions of reverse traceroutes per day. We hope to improve the scalability/throughput going forward.

Just as some hosts are configured not to respond to ping, some hosts do not respond to our measurements. We found that 75% of hosts that respond to ping also respond to our measurements. Of responsive hosts, 63% are within range of our current vantage points. Going forward, we would be able to measure from more than the 39,544 ASes if we add more vantage points in strategic locations where we currently lack coverage and/or (perhaps if our system gains traction) if more operators configure their routers to respond. 

ACCURACY

I think both approaches are similarly accurate. Rolf mentions that revtr-lg "perform[s] the actual measurement between two endpoints, we identify the actual forwarding path, at the router-level, including load-balanced paths." revtr-2.0 also measures the actual forwarding path between the two endpoints, at the router/IP-level, including the ability to uncover the multiple branches of load balanced paths.

We expect that our tool is similarly accurate at the IP and router-level, it's just harder to give exact numbers because tools can return different IP addresses that correspond to the same router, and so we did the comparison at AS level.

Best,

Ethan (and Kevin Vermeulen, Dave Choffnes, and Italo Cunha)