Configuring Performance Rate of Line Modules on ERX7xx Models and the ERX1410 Router

Note: The information in this section does not apply to the ERX1440, ERX310, E120, or E320 router . It also does not apply to the OC48 line module, which is supported only by the ERX1440 router.

Line modules in an ERX1440 or an ERX310 router always operate at line rate performance. However, you can configure ERX7xx models and the Juniper Networks ERX1410 Broadband Services Router to enable the line modules either to operate at full line rate performance or to allow line modules to operate at a rate dependent on the resources available.

Operating at full line rate performance restricts the combination of line modules in the router. Operating at a rate dependent on the resources available allows a much more extensive combination of line modules in the router and is known as bandwidth oversubscription.

To configure performance:

1. Choose a combination of line modules appropriate for the performance. See Choosing a Combination of Line Modules.
2. Disable slots that contain unwanted line modules, or modify the combination of line modules in the router. See Disabling and Reenabling Line Modules, SRP Modules, and SFMs, and ERX Hardware Guide, Chapter 4, Installing Modules.
3. Specify the type of performance. See Specifying the Type of Performance.

Choosing a Combination of Line Modules

For line rate performance, the total bandwidth required by the line modules in the slot group must not exceed the bandwidth available from the SRP module. In this case, the combination of line modules that can reside in a slot group depends on the following:

• The number of slots per group
• The bandwidth available from the SRP module
• The bandwidth required by each line module
• In the case of the SRP-5G+ and SRP-10G modules, the switches (upper and lower) that the line module can use.

Slot Groups

The number of slots in a group depends on the E Series model. For information about slot groups, see ERX Hardware Guide, Chapter 4, Installing Modules.

SRP Modules Bandwidth

Different SRP modules offer different bandwidths:

• The SRP-10G module provides 2.5 Gbps bandwidth per slot group.
• The SRP-5G+ module (ERX705 router only) provides:
  • 2.5 Gbps bandwidth per slot group
  • 5 Gbps bandwidth per router

Line Modules Bandwidth and Switch Usage

The SRP-5G+ and SRP-10G modules comprise two switches; each switch provides 50 percent of the bandwidth.

The line modules in a slot group cannot operate at line rate if:

• The sum of their bandwidths exceeds the bandwidth that the SRP module can supply per slot group.
• The sum of the bandwidths they require from one SRP switch exceeds the bandwidth that the SRP switch can supply per slot group.

Table 40 shows the bandwidth that each line module requires for line rate performance and the switches that the line module can use on the SRP-5G+ and SRP-10G modules.

Allowed Combinations for Line Rate Performance

The SRP-5G+ and SRP-10G modules support all the line modules listed in Table 40.

Only certain combinations of line modules allow line rate performance (see Table 41 through Table 43). However, if performance lower than line rate is acceptable, you can use any combination of line modules in a slot group.

For example, the SRP-10G module offers a total bandwidth of 2.5 Gbps for each slot group. The GE line module requires 2.46 Mbps bandwidth for operation at line rate, and can use both switches in the SRP-10G module. If you require line rate from a GE line module, install only one GE line module in the slot group. However, if lower performance is acceptable, you can install two or three GE line modules in a slot group and enable bandwidth oversubscription.

When bandwidth oversubscription is enabled, all line modules optimize use of the resources available. For example, if two GE line modules are installed in a slot group, each line module is allocated 50 percent of the available bandwidth. However, if one line module is using less bandwidth than it is allocated, the other line module can use more bandwidth than it is allocated and can operate at a greater rate.

Table 41, Table 42, and Table 43 indicate combinations of line modules that allow line rate performance.

Specifying the Type of Performance

After you have installed a suitable combination of line modules, you can specify a different type of performance. To specify the type of performance:

1. Issue the show bandwidth oversubscription command.
2. If the setting is not the one you want, enable or disable bandwidth oversubscription.
3. Reboot the router.

Monitoring Bandwidth Oversubscription

Use the show bandwidth oversubscription and show utilization (see Monitoring Modules) commands to monitor the status of bandwidth oversubscription.

Troubleshooting Bandwidth Oversubscription

If you enter a forbidden combination of line modules or exceed the slot group bandwidth when you have not configured bandwidth oversubscription, you will see an error message.

For example, suppose you originally configure the router for bandwidth oversubscription and then want to change to full line rate performance. You forget to remove line modules or disable slots, and enter the no bandwidth oversubscription command. The following message appears:

To resolve the problem, remove the unwanted line modules, or disable the slots that contain those line modules.