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 the Installing Modules chapter in the ERX Hardware Guide.
  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:

Slot Groups

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

SRP Modules Bandwidth

Different SRP modules offer different bandwidths:

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:

Table 86 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.

Table 86: Bandwidth Statistics for Line Modules

Line Module

Total Bandwidth Required (Gbps)

Switches Used on SRP-5G+ and SRP-10G Modules

cOCx/STMx

2.46

Both switches

COCX-F3

2.46

Both switches

CT3/T3-F0

2.46

Both switches

GE/FE

2.46

Both switches

IPsec Service

2.46

Both switches

OC3/STM1 GE/FE

2.46

Both switches

OCx/STMx ATM

1.22

Both switches

OCx/STMx POS

2.46

Both switches

Allowed Combinations for Line Rate Performance

The SRP-5G+ and SRP-10G modules support all the line modules listed in Table 86.

Only certain combinations of line modules allow line rate performance (see Table 87 through Table 89). 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 87, Table 88, and Table 89 indicate combinations of line modules that allow line rate performance.

Table 87: Combinations of Line Modules for Line Rate Performance—SRP-10G Module in an ERX7xx Model

Possible Combinations of Line Modules

Examples of Allowed Combinations

Examples of Forbidden Combinations

  • One supported line module and one empty slot in slot group 1

    NOTE: The SRP-10G module supports all line modules listed in Table 86.

  • Two OCx/STMx ATM line modules in slot group 1
  • One supported line module in slot groups 2, 3 and 4
  • One OCx/STMx POS line module in slot group 1, a GE/FE line module in slot group 2, and one OCx/STMx ATM line module in slot group 4
  • Two OCx/STMx ATM line modules in slot group 1, one GE/FE line module in slot group 2, and one SM in slot group 3
  • A GE/FE line module and any other line module in slot group 1
  • Two OCx/STMx POS line modules in slot group 1

Table 88: Combinations of Line Modules for Line Rate Performance—SRP-10G Module in an ERX1410 Router

Possible Combinations of Line Modules

Examples of Allowed Combinations

Examples of Forbidden Combinations

  • One supported line module and two empty slots in any slot group

    NOTE: The SRP-10G module supports all line modules listed in Table 86.

  • Two OCx/STMx ATM line modules and one GE/FE module and one empty slot in any slot group (bandwidth oversubscription enabled)
  • One OC3/STM1 GE/FE module in any slot (bandwidth oversubscription disabled)
  • One COCX-F3 line module in slot group 1, a GE/FE line module in slot group 2, and a OCx/STMx POS line module in slot group 3
  • Three OCx/STMx ATM line modules in any slot group
  • Two GE/FE line modules in any slot group

Table 89: Combinations of Line Modules for Line Rate Performance—SRP-5G+ Module in an ERX705 Router

Possible Combinations of Line Modules In Slot Groups

Examples of Allowed Combinations

Examples of Forbidden Combinations

NOTE: The total bandwidth of all line modules must not exceed 5 Gbps. To make optimal use of the available bandwidth, put line modules that require maximum bandwidth in slot 2, 3, or 4.

  • One supported line module and one empty slot in slot group 1

    NOTE: The SRP-5G+ module supports all line modules listed in Table 86.

  • Two OCx/STMx ATM line modules in slot group 1
  • One cOCx/STMx, COCX-F3, CT3/T3 FO, GE/FE, IPsec Service, or OCx/STMx line module in slot groups 2, 3, and 4
  • Two OCx/STMx ATM line modules (total 2.44 Gbps) in slot group 1, and a GE/FE line module (2.46 Gbps) in slot group 4
  • Two OCx/STMx ATM line modules (total 2.44 Gbps) in slot group 1, and a COCX-F3 line module in slot group 2
  • Two OCx/STMx ATM line modules (total 2.44 Gbps) in slot group 1, a GE/FE line module (2.46 Gbps) in slot group 3, and an OCx/STMx POS line module (2.46 Gbps) in slot 4 (violates chassis limitation)
  • Two OCx/STMx POS line modules (total 4.92 Gbps) in slot group 1 (violates slot group limitation)

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.

bandwidth oversubscription

Monitoring Bandwidth Oversubscription

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

show 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:

host1(config)#no bandwidth oversubscription % failed : bandwidth oversubscribed at slot 0-2

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