During normal operations, AppNeta Performance Manager (APM) continuously monitors all network paths using Continuous Path Analysis (CPA). If a problem is detected on a path, APM initiates a diagnostic test to probe the path in more detail to help identify the source of the issue.

Diagnostics help you to pinpoint problematic hops using the same packet dispersion techniques as CPA, but rather than sending test packets only to the target, test packets are sent to all hops on the network path in addition to the target.

For single-ended paths, the diagnostics tests use ICMP for testing both the path hops and the path target. For dual-ended paths, the diagnostics tests in both directions (source-to-target and target-to-source) use ICMP to test path hops and UDP to test the endpoints.

Dual-ended diagnostics restrictions

Diagnostics on dual-ended paths are subject to some restrictions:

  • Diagnostics are only available for dual-ended paths when the source and target monitoring points are in the same organizational hierarchy. If they are not, single-ended diagnostics are run in the outbound direction, and inbound diagnostics are not available.
  • If a hostname is used to identify the target then a hostname must also be used to identify the source. An IP address cannot be used.
  • There are circumstances in which inbound diagnostics (target-to-source), cannot be run:
    • When the source connects to APM via the AppNeta relay server - In this instance, APM does not know the public IP address of the source.
    • When the target and one or more other monitoring points are behind a firewall - In this instance, APM cannot uniquely identify the target.
    • When the firewall in front of the source is blocking inbound UDP - In this instance, the inbound diagnostics cannot be forwarded to the source. Diagnostics revert to ICMP.

Limits to concurrent diagnostic tests

Within a parent or child organization, the number of concurrent diagnostic tests triggered by a violation event is subject to a limit. Once this concurrency limit is reached, a limited number of tests may be queued. Tests triggered when the queue is full are skipped. Skipped events are marked on the Capacity chart. Diagnostics initiated manually, or triggered when a path is created, are never skipped.

Note that the path status changes to “testing” only when the test starts, not while it is queued.

Triggering diagnostics

In addition to being triggered automatically when an alert condition is violated, diagnostics are also triggered automatically when a network path is created. In addition they can be triggered manually.

To initiate a diagnostic test manually:

  1. Navigate to Delivery > Network Paths.
  2. Click the network path you are interested in.
  3. In the Network Path Details panel, click Diagnose.
    • The diagnostic testing begins.

View diagnostic results

To view the diagnostic test results for a network path:

  1. Navigate to Delivery > Network Paths.
  2. Click the network path you are interested in.
  3. In the Network Path Details panel, click the link next to Diagnostic.

Summary tab

The Summary tab provides a high level summary of the information obtained during the diagnostic test. This includes:

  • Hop diagram - shows the source, the target, and all hops between the source and target. In addition, it provides a number of metrics for the path. Hovering over a hop provides hop details.
  • Diagnostics section - provides diagnostic messages that describe issues detected. Clicking on a message provides a detailed explanation of the message and recommended actions for resolving the issue.
  • Recommendations section - provides suggestions for resolving the issues found.
  • Host name table - provides hostnames and IP addresses for each hop.

Data and voice details tabs

The Data Details and Voice Details tabs provide per-hop details. This includes:

  • Hop diagram - shows the source, the target, and all hops between the source and target. In addition, it provides a number of metrics for the path. Hovering over a hop provides hop details.
  • Hop table - provides per-hop detail including:
    • Severity - icons that indicate the diagnostic severity. See the table below for details.
    • Network performance metrics - showing the metrics that could be measured or calculated. Note that, for voice handsets and network responder target types, mid-path analysis is not performed during diagnostics tests. Mid-path device shows lower capacity than the target explains how it is possible to see lower capacity on mid-path devices than on the target.
    • QoS - shows what DSCP value was set on the packet and what was returned by the network device. This allows you to determine how the DSCP value is being affected by each hop. If a DSCP value is set but the “Measured” column shows “-“, it means that the network device returned a different DSCP value when probed using ICMP then when probed using UDP.
    • Additional detail (by clicking a table row)
      • Observations are network conditions that were witnessed during the test; they’re rated by frequency in terms of percentage of packets sent or percentage of times the condition was witnessed. For example, if ‘packet reordering detected’ has a 12% frequency, then 12% of the packets in the train sent to the hop arrived out of their original sequence. Some observations don’t have a frequency because the relevant portion of the diagnostic was only performed once.
      • Diagnostics appear when a network condition can be inferred from the measurements taken. They are rated by certainty from 0 to 100%.

Diagnostic severity icon meanings

Icon Severity Description
ok.svg OK Nothing to report.
informational.svg Information Information about a hop.
warning.svg Warning The hop is impacting performance.
connectivity-lost.svg Indeterminate The hop could not be measured.
violated.svg Error The hop is severely impacting path performance.

The Related Network Devices tab lists each hop in a path, and gives you the opportunity to save the hop’s details so that APM can poll it via SNMP. If a hop is under your administrative control, click Add Device. Complete the dialog that follows, and an initial SNMP Walk begins immediately. Then click a table row to see polling results.

Download a report

Diagnostics information is also provided in report format.

To download a Test Results Report:

  1. Navigate to Delivery > Network Paths.
  2. Click the network path you are interested in.
  3. In the Network Path Details panel, click the link next to Diagnostic.
  4. Select > Download PDF.
    • The Test Results Report for the selected path is downloaded to your computer.