  BGP-Multipath (BGP-M) is a multipath routing technique for load balancing.
Distinct from other techniques deployed at a router inside an Autonomous System
(AS), BGP-M is deployed at a border router that has installed multiple
inter-domain border links to a neighbour AS. It uses the equal-cost multi-path
(ECMP) function of a border router to share traffic to a destination prefix on
different border links. Despite recent research interests in multipath routing,
there is little study on BGP-M. Here we provide the first measurement and a
comprehensive analysis of BGP-M routing in the Internet. We extracted
information on BGP-M from query data collected from Looking Glass (LG) servers.
We revealed that BGP-M has already been extensively deployed and used in the
Internet. A particular example is Hurricane Electric (AS6939), a Tier-1 network
operator, which has implemented >1,000 cases of BGP-M at 69 of its border
routers to prefixes in 611 of its neighbour ASes, including many hyper-giant
ASes and large content providers, on both IPv4 and IPv6 Internet. We examined
the distribution and operation of BGP-M. We also ran traceroute using RIPE
Atlas to infer the routing paths, the schemes of traffic allocation, and the
delay on border links. This study provided the state-of-the-art knowledge on
BGP-M with novel insights into the unique features and the distinct advantages
of BGP-M as an effective and readily available technique for load balancing.
