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Publications Technical Report

New Tech Report “Detecting Internet Outages with Precise Active Probing (extended)”

We just published a new technical report “Detecting Internet Outages with Precise Active Probing (extended)”, available at ftp://ftp.isi.edu/isi-pubs/tr-678b.pdf. This is an update of ISI-TR-678.

From the abstract:

Parts of the Internet are down every day, from the intentionalshutdown of the Egyptian Internet in Jan. 2011 and natural disasterssuch as the Mar. 2011 Japanese earthquake, to the thousands of smalloutages caused by localized accidents, and human error, maintenance,or choices.  Understanding these events requires efficient andaccurate detection methods, motivating our new system to detectnetwork outages by active probing.  We show that a single computer cantrack outages across the entire analyzable IPv4 Internet, probing asample of 20 addresses in all 2.5M responsive /24 address blocks.  Weshow that our approach is significantly more accurate than the bestcurrent methods, with 31% fewer false conclusions, while providing 14%greater coverage and requiring about the same probing traffic.  Wedevelop new algorithms to identify outages and cluster them to events,providing the first visualization of outages.  We carefully validateour approach, showing consistent results over two years and from threedifferent sites.  Using public BGP archives and news sources weconfirm 83% of large events.  For a random sample of 50 observedevents, we find 38% in partial control-plane information, reaffirmingprior work that small outages are often not caused by BGP.  Throughcontrolled emulation we show that our approach detects 100% offull-block outages that last at least twice our probing interval.Finally, we report on Internet stability as a whole, and the size andduration of typical outages, using core-to-edge observations with muchlarger coverage than prior mesh-based studies.  We find that about0.3% of the Internet is likely to be unreachable at any time,suggesting the Internet provides only 2.5 “nines” of availability.

Categories
Publications Technical Report

New tech report “Characterizing Anycast in the Domain Name System”

We just published an new technical report of our anycast enumeration work, including some exciting new results. Check out “Characterizing Anycast in the Domain Name System” (available at ftp://ftp.isi.edu/isi-pubs/tr-681.pdf) .

From the abstract:

IP anycast is a central part of production DNS. While prior
work has explored proximity, affinity and load balancing
for some anycast services, there has been little attention to
third-party discovery and enumeration of components of an
anycast service. Enumeration can reveal abnormal service
configurations, benign masquerading or hostile hijacking of
anycast services, and can help characterize the extent of any-
cast deployment. In this paper, we discuss two methods to
identify and characterize anycast nodes. The first uses an
existing anycast diagnosis method based on CHAOS-class
DNS records but augments it with traceroute to resolve
ambiguities. The second proposes Internet-class DNS records
which permit accurate discovery through the use of existing
recursive DNS infrastructure. We validate these two meth-
ods against three widely-used anycast DNS services, using
a very large number (60k and 300k) of vantage points, and
show that they can provide excellent precision and recall.
Finally, we use these methods to evaluate anycast deploy-
ments in top-level domains (TLDs), and find one case where
a third-party operates a server masquerading as a root DNS
anycast node as well as a noticeable proportion of unusual
anycast proxies. We also show that, across all TLDs, up to
72% use anycast, and that, of about 30 anycast providers,
the two largest serve nearly half the anycasted TLD name-
servers.

Citation: Xun Fan, John Heidemann and Ramesh Govindan. Characterizing Anycast in the Domain Name System. Technical Report N. ISI-TR-681, USC/Information Sciences Institute, May, 2012. ftp://ftp.isi.edu/isi-pubs/tr-681.pdf