Active Measurements
	• Topology probing related: – rfc1918 or other non-routed addresses for intermediaries – IP addresses of interfaces, not routers – different interfaces (inbound/outbound) may respond to TTL exceed depending on vendor (contrary to RFC) – primary path followed, may not see backup paths – straight topology says nothing about importance, usage, or capacity – some methodologies completely discard prefix-based routing policy – resulting graph is a “time smear” over entire collection interval
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