RTT Monitor

The Round Trip Time (RTT) Monitor is available under the System Interface. The RTT monitor probes configured hosts on a minute-by-minute basis to check:

• IP reachability.
• Functionality of certain services.

Checks account for the RTT, that is, the time it takes to reach a certain host and receive a response from it. The following probes can be used to measure the RTT:

• ICMP and ICMPv6: to check host IP reachability.
• HTTP and HTTPS: to check functionalities of possible host web servers.

All the RTT-monitored hosts are shown in a table.

The RTT Monitor Table

The table has the following columns:

• URL: The full URL of the monitored host. The URL is the concatenation of the host name or IP address with a prefix which indicates the type of probe, namely one of icmp, icmpv6, http or https.
• chart: A link to the RTT chart, present when RTT Timeseries are enabled.
• RTT Threshold: A threshold, expressed in milliseconds, used to trigger RTT Alerts.
• Last Measurement: The time of the last measurement performed.
• Last IP: The latest IP address resolved for the host name indicated in the URL.
• Measurement Time: The value, in milliseconds, of the latest measured RTT.
• Actions: Buttons to delete or edit the configured host.

Hosts can be added to the RTT monitor using the plus sign in the top-right corner of the table.

The RTT Add Record Pane

Three fields need to be input when adding a host:

• measurement: The type of probe.
• host: The host name or the IP address of the host which needs to be monitored
• rtt threshold: A threshold, expressed in milliseconds, used to trigger RTT Alerts.

RTT Alerts

Alerts are triggered when the measured RTT is above the configured threshold, or when the host is unreachable. Configuring a threshold is contextual to the addition of an host among those monitored. Alerts are shown under the triangle entry of the RTT menu bar.

The RTT Alerts

Alerts can either be engaged, for currently ongoing issues, or past, for issues occurred in the past.

RTT Timeseries

RTT timeseries are written automatically by default for any of the RTT-monitored hosts.

The RTT Timeseries of a Monitored Host

Timeseries can be disabled from the ntopng Settings, tab Timeseries->System Probes.

The RTT Timeseries Configuration

In case of HTTP monitoring, the “HTTP Stats” timeseries show more insights on the HTTP traffic:

• Name Lookup: time spent resolving the host name
• App Connect: time spent in the SSL handshake
• Other: remaining time for the HTTP request and response