TTLmeting
TTLmeting is the practice of measuring the time-to-live (TTL) field in IP packets to characterize network paths and devices. The TTL is an 8-bit value set by the sender and decremented by each router it traverses; when the TTL reaches zero, the packet is discarded and an ICMP Time Exceeded message may be returned. Because TTL values are typically observed in responses, TTLmeting can reveal hop counts, routing behavior, and, to some extent, the operating system characteristics of intermediate devices.
Methods of TTLmeting can be active or passive. Active measurement uses traceroute-like techniques that elicit responses
Applications of TTLmeting include topology discovery, troubleshooting routing issues, estimating latency and path stability, and aiding