ohohlfeld.com : blog
Internet cartography is a serious and challenging research topic. Such maps are useful for e.g. evaluating applications and algorithms in simulation. As Rob Sherwood, who is now with Deutsche Telekom USA, highlighted when taking question after his talk given at ACM Sigcomm 2008 about DisCarte: we have conferences dealing with Internet Measurement, but we don’t know how exactly the Internet looks like. While traceroute, as an active measurement technique, it highlights parts of the Internet topology, other parts are hidden as routers don’t respond to traceroutes’ probes and are thus not visible. Moreover, traceroute will reveal only interfaces and not the routers itself. As routers are usually equipped with many interfaces, mapping interfaces obtained from traceroute probes to routers is another issue that makes Internet cartography a complex activity. In his paper, Rob Sherwood proposed a combined approach, which makes use of the Record Route (RR) mechanism provided by IP (cf. RFC 791) and outperforms current mapping techniques. The offered record route option will maintain a set of IP addresses (up to a certain length) used to record the route of an Internet datagram. Obviously, it is merely a matter of time until network providers which want to obfuscate their backbone topology configure their routers to no longer append their addresses to the RR list, but I agree with Sherwood’s view: having an, maybe, old but rather accurate map of the Internet is better than nothing.
While traceroute represents an active measurement approach, partial information about the network topology can also be obtained from passive measurements, as Brian Eriksson, who is with the University of Wisconsin-Madison, showed in his Sigcomm 2008 paper. However, a certain degree of active probes are still necessary, as Eriksson highlighted in his talk.
Map sources:
- A source of publicy available topologies of commercial and research backbone networks, which can be directly fed into simulators, can be found here.
- Internet Mapping Project: Larger number of maps maintained until 2000.
- Backbone maps as pixel graphics can be found here.
- EPFL’s netscope is designed to monitor overlay networks
If you know of more mapping sources, please place a link in the comments of this post. Many thanks in advance.
