[lacnog] Internet Anycast: Performance, Problems, & Potential
gael en pch.net
Mar Sep 25 05:52:33 BRT 2018
Hola a todos,
Para aquellos con interés en el enrutamiento IP anycast y su
rendimiento, un nuevo paper sobre el tema
Internet anycast depends on inter-domain routing to direct clients to
their “closest” sites. Using data collected from a root DNS server
for over a year (400M+ queries/day from 100+ sites), we characterize the
load balancing and latency performance of global anycast. Our analysis
shows that site loads are often unbalanced, and that most queries travel
longer than necessary, many by over 5000 km.
Investigating the root causes of these inefficiencies, we can attribute
path inflation to two causes. Like unicast, anycast routes are subject
to inter-domain routing topology and policies that can increase path
length compared to theoretical shortest (e.g., great-circle distance).
Unlike unicast, anycast routes are also affected by poor route selection
when paths to multiple sites are available, subjecting anycast routes to
an additional, unnecessary, penalty.
Unfortunately, BGP provides no information about the number or goodness
of reachable anycast sites. We propose an additional hint in BGP
advertisements for anycast routes that can enable ISPs to make better
choices when multiple “equally good” routes are available. Our
results show that use of such routing hints can eliminate much of the
anycast path inflation, enabling anycast to approach the performance of
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