[lacnog] Internet Anycast: Performance, Problems, & Potential

Gael Hernandez 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 
unicast routing.

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