Mark Allman / ICSI @mallman_icsi

Philipp Richter, Florian Wohlfart, Narseo Vallina-Rodriguez, Mark Allman, Randy Bush, Anja Feldmann, Christian Kreibich, Nicholas Weaver, Vern Paxson. A Multi-perspective Analysis of Carrier-Grade NAT Deployment. ACM Internet Measurement Conference, November 2016.
PDF | Philipp's Slides | arXiv


As ISPs face IPv4 address scarcity they increasingly turn to network address translation (NAT) to accommodate the address needs of their customers. Recently, ISPs have moved beyond employing NATs only directly at individual customers and instead begun deploying Carrier-Grade NATs (CGNs) to apply address translation to many independent and disparate endpoints spanning physical locations, a phenomenon that so far has received little in the way of empirical assessment. In this work we present a broad and systematic study of the deployment and behavior of these middleboxes. We develop a methodology to detect the existence of hosts behind CGNs by extracting non-routable IP addresses from peer lists we obtain by crawling the BitTorrent DHT. We complement this approach with improvements to our Netalyzr troubleshooting service, enabling us to determine a range of indicators of CGN presence as well as detailed insights into key properties of CGNs. Combining the two data sources we illustrate the scope of CGN deployment on today's Internet, and report on characteristics of commonly deployed CGNs and their effect on end users.


    author      = "Philipp Richter and Florian Wohlfart and Narseo Vallina-Rodriguez and Mark Allman and Randy Bush and Anja Feldmann and Christian Kreibich and Nicholas Weaver and Vern Paxson",
    title       = "{A Multi-perspective Analysis of Carrier-Grade NAT Deployment}",
    booktitle   = "ACM SIGCOMM Internet Measurement Conference",
    year        = 2016,
    month       = nov,

This paper is the recipient of the IRTF Applied Networking Research Prize, 2017.

Philipp gave a talk on this work at RIPE-73 (October 2016). A video of his talk is here and his slides are here.
"We are what we repeatedly do. Excellence, then, is not an act, but a habit." --Aristotle