PerHop

Perhop, commonly written as per-hop, is a term used in computer networking to describe metrics attributed to an individual hop along a path from a source to a destination. A hop typically corresponds to a forwarding device, such as a router, that passes a packet to the next element on the route. Per-hop metrics focus on the performance characteristics observed at each transition, rather than only the overall end-to-end result.

Common per-hop metrics include latency, which measures the delay added by a hop; packet loss, the fraction of packets that fail to be forwarded correctly at that hop; and available bandwidth or throughput on the link leading to the next hop. Per-hop latency reflects processing, queuing, and transmission times at each device and can vary with traffic patterns. Per-hop data are often used to identify where in a path bottlenecks occur and to assess the quality of individual segments of a network path.

Per-hop information is widely used in network troubleshooting and performance monitoring. Tools such as traceroute, pathping, and modern equivalents report per-hop round-trip times and packet loss, enabling operators to localize issues. Per-hop measurements also contribute to network planning, capacity analysis, and quality-of-service decisions. They complement end-to-end metrics, which summarize performance across all hops.

Limitations include variability due to routing changes, transient congestion, and measurement artifacts. Some devices may rate-limit or deprioritize probing traffic, distorting per-hop data. Despite these caveats, per-hop metrics provide granular insight into network behavior and remain a standard concept in performance analysis and diagnostics.