R&E Global LPP Report

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Why this report exists

The global R&E network consists of roughly 2,700 separate networks (autonomous systems). A significant percentage of these networks have connections to both an upstream R&E provider and one or more commodity ISPs. Each network independently makes routing decisions about which path to prefer when reaching various destinations.

Campuses typically connect to a regional R&E network (e.g., MERIT, LEARN, CENIC, NYSERNet), which in turn connects to Internet2. The R&E route between two campuses is often at least 4 AS hops. If both campuses use the same commodity ISP—which happens frequently—the commodity route might only be 2 hops. Without an explicit routing policy, BGP selects the shortest AS path, and the two campuses will route via the commodity ISP instead of the R&E network.

The recommended best practice is to use BGP Local Preference to prefer routes learned from R&E networks over routes learned from commodity ISPs. When this is done, campuses route via the R&E path regardless of AS-path length.

How the probe works

The Local Preference Probe (LPP) is a server connected to both the Internet2 R&E network and a commodity ISP. It sends probes from two source addresses to hosts across the 2,700 R&E networks and observes how each network routes its response back—does it arrive via the R&E path or the commodity path?

Source	Address	Route design
Source A	163.253.64.1	R&E route is prepended towards commodity
Source B	163.253.63.63	R&E route is prepended towards R&E

Both sources share the same commodity route. The difference is which direction the R&E route is prepended, so the two probes test whether the remote network chooses based on Local Preference or AS-path length.

Reading the results

Color	Source A	Source B	Meaning
RE	R&E	R&E	The network is following the best practice of preferring R&E routes over commodity. BGP Local Preference favors R&E.
Path	R&E	Commodity	The network is using AS-path length to choose, so some destinations use R&E while others route via commodity. R&E and commodity have equal Local Preference.
Comm	Commodity	Commodity	The network appears to always prefer commodity, even when an R&E route exists.
Inconclusive	Missing / unexpected		Excluded from percentages.

Orange and red networks are connected to the global R&E network infrastructure, but are not effectively using it.

Customer cone percentages

The stacked bar for each AS shows the breakdown of classified probes across its customer cone—the AS itself plus every AS downstream of it in the R&E tree.

• Each probed destination IP is classified as RE, Comm, or Path (inconclusive excluded).
• Counts are summed across the entire cone: the AS's own prefixes plus all downstream prefixes.
• The three segments are each category's share of the cone total, summing to 100%.

A leaf AS shows only its own results. A transit AS near the root aggregates results across hundreds of downstream networks, giving a high-level view of routing policy in that part of the R&E topology.

Navigating the tree

• Search: type an AS number or name to highlight matches and auto-expand their location in the tree.
• Sort: click the RE, Comm, Path, or Pfx headers to sort children within each expanded subtree.
• Duplicates: an AS that appears under multiple parents is fully rendered only once. Subsequent appearances show a see above link that scrolls to the first occurrence.

Data sources

RouteViews (BGP paths & origins), RIPE Stat (AS names), CAIDA (fallback names), lpp-store (probe results). Report rebuilds daily at UTC midnight.

Part of the CICI-ROOTBEER project.