Diagnostic Capabilities of Pathping in Windows 2000

The pathping command-line tool in Microsoft Windows 2000 is an advanced network diagnostic utility that combines the functionality of ping and tracert with detailed packet-loss and latency statistics. Over an extended sampling period, pathping traces the route to an IP destination, sends multiple echo requests to each router along the path, and computes statistical results to pinpoint precisely which network hops or links are causing packet loss or latency issues.

Route Tracing and Hop Identification

Like the standard tracert utility, pathping begins its diagnostics by discovering the intermediate hops (routers) between the local host and the target system. It uses Internet Control Message Protocol (ICMP) echo packets with incrementing Time-to-Live (TTL) values to map out the full network path, displaying each router's IP address and hostname.

Hop-by-Hop Packet Loss Calculation

After mapping the route, pathping monitors each intermediate router over a designated time interval (typically 25 seconds by default, scalable by the number of hops). It sends multiple ICMP Echo requests to each node along the path. By analyzing the returned packets, the tool computes:

  • Node Loss: The percentage of packets dropped directly by a specific router, indicating router congestion or CPU exhaustion.
  • Link Loss: The percentage of packets dropped across the network link between two routers, helping administrators detect failing physical connections or saturated bandwidth.

Latency and Round-Trip Time (RTT) Metrics

pathping records the round-trip times to each hop during the discovery and sampling phases. By evaluating changes in RTT from one hop to the next, administrators can identify specific segments of the network experiencing propagation delay, queuing delays, or routing bottlenecks.

Quality of Service (QoS) and RSVP Diagnostics

Windows 2000 introduced enhanced networking capabilities, including native support for Quality of Service (QoS). The Windows 2000 implementation of pathping includes switches to diagnose traffic prioritization:

  • Layer 2 Priority Tagging (-T): Attaches an 802.1p priority tag to ping packets to determine if intermediate devices properly forward prioritized Layer 2 frames.
  • RSVP Path Testing (-R): Checks whether intermediate routers support the Resource Reservation Protocol (RSVP) for guaranteed bandwidth paths.

Configurable Test Parameters

The tool provides several switches in Windows 2000 to customize diagnostic depth:

  • -n: Prevents the tool from resolving IP addresses to hostnames, speeding up the diagnostic process.
  • -h <MaximumHops>: Sets the maximum number of hops to search for the target.
  • -p <Period>: Defines the pause duration (in milliseconds) between individual pings (default is 250 ms).
  • -q <NumQueries>: Sets the number of queries sent to each router along the path (default is 100 queries per hop).
  • -w <Timeout>: Specifies the wait time (in milliseconds) for each reply before timing out.