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Resource Monitoring Usage Computation Overview


You can configure the resource monitoring capability using both the CLI and SNMP MIB queries. You can employ this utility to provision sufficient headroom (memory space limits that are set for the application or virtual router) for monitoring the health and operating efficiency of DPCs and MPCs. You can also analyze and view the usage or consumption of memory for the jtree memory type and for contiguous pages, double words, and free memory pages. The jtree memory on all MX Series router Packet Forwarding Engines has two segments: one segment primarily stores routing tables and related information, and the other segment primarily stores firewall-filter-related information. As the allocation of more memory for routing tables or firewall filters might disrupt the forwarding operations of a Packet Forwarding Engine, the Junos OS CLI displays a warning to restart all affected FPCs when you commit a configuration that includes the memory-enhanced route statement.

The following sections describe the computation equations and the interpretation of the different memory regions for I-chip-based and Trio-based line cards:

Resource Monitoring and Usage Computation For Trio-Based Line Cards

In Trio-based line cards, memory blocks for next-hop and firewall filters are allocated separately. Also, an expansion memory is present, which is used when the allocated memory for next-hop or firewall filter is fully consumed. Both next-hop and firewall filters can allocate memory from the expansion memory. The encapsulation memory region is specific to I-chip-based line cards and it is not applicable to Trio-based line cards. Therefore, for Trio-based line cards, the percentage of free memory space can be interpreted as follows:

% Free (NH) = (1- (Used NH memory + Used Expansion memory ) / (Total NH memory+Total Expansion memory)) × 100

% Free (Firewall or Filter) = (1-(Used FW memory+Used Expansion memory ) / (Total FW memory+Total Expansion memory)) × 100

Encapsulation memory is I-chip-specific and is not applicable for Trio-based line cards.

% Free (Encap memory) = Not applicable

Resource Monitoring and Usage Computation For I-Chip-Based Line Cards

I-chip-based line cards contain 32 MB of static RAM (SRAM) memory associated with the route lookup block and 16 MB of SRAM memory associated with the output WAN block.

The route-lookup memory is a single pool of 32 MB memory that is divided into two segments of 16 MB each. In a standard configuration, segment 0 is used for NH and prefixes, and segment 1 is used for firewall or filter. This allocation can be modified by using the route-memory-enhanced option at the [edit chassis] hierarchy level. In a general configuration, NH application can be allocated memory from any of the two segments. Therefore, the percentage of free memory for NH is calculated on 32 MB memory. Currently, firewall applications are allotted memory only from segment 1. As a result, the percentage of free memory to be monitored for firewall starts from the available 16 MB memory in segment 1 only.

For I-chip-based line cards, the percentage of free memory space can be interpreted as follows:

% Free (NH) = (32-(Used NH memory+Used FW memory+Used Other application)) / 32×100

% Free (Firewall or Filter)=(16-(Used NH memory+Used FW memory+Used Other application)) / 16×100

The memory size for Output WAN (Iwo) SRAM is 16 MB and stores the Layer 2 descriptors that contain the encapsulation information. This entity is a critical resource and needs to be monitored. This memory space is displayed in the output of the show command as “Encap mem”. The percentage of free memory for the encapsulation region is calculated as follows:

% Free (Encapsulation memory) = (16-(Iwo memory used ( L2 descriptors +other applications))) / 16×100

The watermark level configured for next-hop memory is also effective for encapsulation memory. Therefore, if the percentage of free memory for encapsulation region falls below the configured watermark, logs are generated.

If the free memory percentage is lower than the free memory watermark of a specific memory type, the following error message is recorded in the syslog:

“Resource Monitor: FPC <slot no> PFE <pfe inst> <“JNH memory” or “FW/ Filter memory”> is below set watermark <configured watermark>”.

You can configure resource-monitoring tracing operations by using the traceoptions file <filename> flag flag level level size bytes statement at the [edit system services resource-monitor] hierarchy level. By default, messages are written to /var/log/rsmonlog. The error logs associated with socket communication failure (between the Routing Engine and the Packet Forwarding Engine) are useful in diagnosing the problems in the communication between the Routing Engine and the Packet Forwarding Engine.

From the Ukern perspective, MPC5E contains only one Packet Forwarding Engine instance. The show chassis fabric plane command output displays the state of fabric plane connections to the Packet Forwarding Engine. Because two Packet Forwarding Engines exist, you notice PFE-0 and PFE-1 in the output.

Because only one Packet Forwarding Engine instance for MPC5E exists, the output of the show system resource-monitor fpc command displays only one row corresponding to Packet Forwarding Engine instance 0.

The configured watermark is retained across GRES and unified ISSU procedures.

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