Understanding Using Probes for Real-Time Performance Monitoring on M, T, ACX, MX, and PTX Series Routers, EX and QFX Switches

Real-time performance monitoring (RPM) enables you to configure active probes to track and monitor traffic. Probes collect packets per destination and per application, including PING Internet Control Message Protocol (ICMP) packets, User Datagram Protocol and Transmission Control Protocol (UDP/TCP) packets with user-configured ports, user-configured Differentiated Services code point (DSCP) type-of-service (ToS) packets, and Hypertext Transfer Protocol (HTTP) packets. RPM provides Management Information Base (MIB) support with extensions for RFC 2925, Definitions of Managed Objects for Remote Ping, Traceroute, and Lookup Operations.

When RPM is configured on a Junos device, the device calculates network performance based on packet response time, jitter, and packet loss. The device gathers RPM statistics by sending out probes to a specified probe target, identified by an IP address. When the target receives a probe, it generates responses that are received by the device.

Starting in Junos OS Release 17.3R1, you can apply RPM to IPsec tunnels and GRE tunnels for PIC-based and Routing Engine-based RPM clients and servers if you are using MS-MPCs or MS-MICs. Packet Forwarding Engine-based RPM is not supported for IPsec tunnels. Support of RPM on IPSec tunnels enables service level agreement (SLA) monitoring for traffic transported in IPSec tunnels.

Starting in Junos OS Evolved Release 20.1R1, you can configure RPM probes. For Junos OS Evolved, RPM is configured at the [edit services monitoring rpm] hierarchy level. The scope of support is limited to:

• Probe generation and reception (client) as well as reflection (server) for the following RPM probe types:

  • http-get (added in Junos OS Evolved 23.4R1)

    You must set the offload-type statement to none to configure this probe type.

  • http-metadata-get (added in Junos OS Evolved 23.4R1)

    You must set the offload-type statement to none to configure this probe type.

  • icmp-ping

  • icmp-timestamp

  • tcp-ping (added in Junos OS Evolved 23.4R1)

    You must set the offload-type statement to none to configure this probe type.

  • udp-ping

  • udp-timestamp

• Probe history management

• Reporting through syslog only

Starting in Junos OS Evolved Release 21.2R1, reporting through SNMP MIB objects is supported for RPM. For more information about SNMP MIBs that Juniper supports, see SNMP MIB Explorer.

In Junos OS, you can also configure RPM services to determine automatically whether a path exists between a host device and its configured BGP neighbors. You can view the results of the discovery using an SNMP client. Results are stored in pingResultsTable, jnxPingResultsTable, jnxPingProbeHistoryTable, and pingProbeHistoryTable.

Starting in Junos OS Release 18.4R1 for MX Series routers, you can use RPM probes to detect link status, and change the preferred-route state on the basis of the probe results. RPM-tracked routes can be IPv4 or IPv6, and support a single IPv4 or IPv6 next hop. You configure this feature with the rpm-tracking statement at the [edit routing-options] or [edit routing-instances routing-options] hierarchy level. For example, RPM probes can be sent to an IP address to determine if the link is up, and if so, the software installs a static route in the route table. RPM-tracked static routes are installed with preference 1 and thus are preferred over any existing static routes for the same prefix. Starting in Junos OS Release 19.1R1, you can track up to 16 next hops for each IPv4 or IPv6 RPM-tracked static route, for MX Series routers. Starting in Junos OS Release 20.4R1, we've extended support to the PTX Series routers. In addition, for this feature, you can configure route preference and tag values for each IPv4 or IPv6 destination prefix. Starting in Junos OS Release 22.3R1, you can configure RPM-tracked static routes for the ACX710 and ACX5448 routers.

In Junos OS, probe configuration and probe results are supported by both the command-line interface (CLI) and SNMP. You set the probe options in the test test-name statement at the [edit services rpm probe owner] hierarchy level. You use the show services rpm probe-results command to view the results of the most recent RPM probes.

The following probe types are supported with DSCP marking:

• HTTP get (not available for BGP RPM services)

• ICMP echo

• ICMP timestamp

• TCP connection

• UDP echo

• UDP timestamp

With probes, you can monitor:

• Average round-trip time

• Jitter of the round-trip time—The difference between the minimum and maximum round-trip time

• Maximum round-trip time

• Minimum round-trip time

• Standard deviation of the round-trip time (Junos OS only)

One-way measurements for ICMP timestamp probes include:

• Minimum, maximum, standard deviation, and jitter measurements for egress and ingress times

• Number of probe responses received

• Number of probes sent

• Percentage of lost probes

You can configure the following RPM thresholds:

• Ingress/egress delay

• Jitter

• Round-trip time

• Standard deviation (Junos OS only)

• Successive lost probes

• Total lost probes (per test)

You can also configure CoS classifiers and prioritization of RPM packets over regular data packets received on an input interface with the dscp-code-points configuration statement.

Table 1 provides information about RPM and related timestamp support on MPC, MS-MIC/MPC, and Routing Engine: