How far can you get with IX Route Servers?#

Ben Cartwright-Cox — bgp.tools / Port 179 LTD

• Why: Takes a peering design question ("can I run route-server-only?") and answers it with real measurement, using a genuinely clever data-plane technique for the part BGP cannot signal. Directly relevant to BGP/peering work.
• What: Across 113 IXes (bgp.tools collector presence), outbound RS-only reachability is 56.6% of the IPv4 DFZ (557,996 of 986,502 prefixes) and 60% of IPv6. Inbound is the surprise: BGP gives no "I accepted your prefix" signal, so he announced a dedicated prefix (203.10.63.0/24, courtesy APNIC/Geoff Huston) to all route servers, then pinged known-responsive hosts sourcing from that prefix — replies return only if the target network actually imports RS routes. Result: only 14.3% of testable prefixes can reach an RS-only network; 85% cannot. Three big European IXes alone yield 12% vs 14.3% for all 113 — a small set of large downstream-heavy networks dominates. Many networks export to RS; few import (131k vs 558k prefixes).
• How: RIB-diffing for outbound; ICMP-source-prefix probing via bgp.tools "IX satellite machines" for inbound, reusing its naughty-packet detection pipeline to attribute which networks replies came from (top sources: BBIX Tokyo/Singapore, DE-CIX FRA — China Mobile Intl, Bharti, FPT, Telkom Indonesia, RETN, EdgeUno).
• Where applicable: Survey is specific to the 113 IXes bgp.tools inhabits (notably excluding Equinix IX and Internet Australia/IX Australia). Caveats stated by the speaker: 60% of prefixes ≠ 60% of traffic (eyeball traffic concentrates in ~5 ASNs), and more-specific TE announcements aren't captured. Oceania-only RS presence yields just 4.8%/0.51% depending on direction. Directly useful for transit-vs-RS-only strategy in the region.