Configuring Performance Rate of Line Modules

Note: This section does not apply to the ERX-1440 system or the OC48 line module, which is only supported by the ERX-1440 system.

Line modules in an ERX-1440 system always operate at line rate performance. However, you can configure the ERX-700 series and the ERX-1410 system 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 system. Operating at a rate dependent on the resources available allows a much more extensive combination of line modules in the system 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, later in this chapter.
2. Disable slots that contain unwanted line modules, or modify the combination of line modules in the system. See Disabling and Reenabling Modules, earlier in this chapter, and ERX Installation and User Guide, Chapter 3, Installing ERX Modules.
3. Specify the type of performance. See Specifying the Type of Performance, later in this chapter.

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.

Note: The SRP-5G module does not support the cOCx/STMx, CT3/T3-FO, COCX-F3, GE/FE, IPSec Service, OCx/STMx or TSM line modules.

Slot Groups

The number of slots in a group depends on the ERX model. For information about slot groups, see ERX Installation and User Guide, Chapter 3, Installing ERX Modules.

SRP Modules Bandwidth

Different SRP modules offer different bandwidths:

• The SRP-5G module provides 1.25 Gbps bandwidth per slot group.
• The SRP-10G module provides 2.5 Gbps bandwidth per slot group.
• The SRP-5G+ module (ERX-705 system only) provides:

• 2.5 Gbps bandwidth per slot group
• 5 Gbps bandwidth per system

Line Modules Bandwidth and Switch Usage

The SRP-5G module has one switch that supplies 100% of the bandwidth for line modules. However, the SRP-5G+ and SRP-10G modules comprise two switches; each switch provides 50% 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.

For example, the T3 line module requires 0.54 Gbps bandwidth and uses only the top switch of the SRP-10G module. To operate three T3 line modules in a slot group at line rate, you would need 1.62 Gbps bandwidth from the top switch. The top switch of the ERX-1410 system offers 1.25 Gbps bandwidth per slot group. Three T3 line modules cannot operate at line rate with an SRP-10G module.

Table 5-1 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 5-1 Bandwidth statistics for line modules 

Line Module	Total Bandwidth Required (Gbps)	Switches Used on SRP-5G+ and SRP-10G Modules
CE1	0.20	Top switch only
cOCx/STMx1	2.46	Both switches2
COCX-F3a	2.46	Both switchesb
CT1	0.20	Top switch only
CT3	0.54	Top switch only
CT3/T3-F0a	2.46	Both switchesb
E3	0.54	Top switch only
FE-2	0.52	Either switch
GE/FEa	2.46	Both switchesb
HSSI	0.54	Top switch only
IPSec Servicea	2.46	Both switchesb
OCx/STMx ATMa	1.22	Both switches3
OCx/STMx POSa	2.46	Both switchesb
T3	0.54	Top switch only
TSMa	2.46	Both switchesb
X.21/V.35	0.20	Top switch only

Allowed Combinations for Line Rate Performance

The SRP-5G+ and SRP-10G modules support all the line modules listed in Table 5-1. This table also indicates which line modules the SRP-5G module supports.

Only certain combinations of line modules allow line rate performance (see Table 5-2 through Table 5-5). 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, except the FE-2 line module, 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% 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. The FE-2 line module uses a fixed portion of the available bandwidth; it cannot take advantage of resources unused by other line modules.

To ensure the best performance, when you change line modules in a slot group that contains an FE-2 line module, you should optimize the bandwidth. See Optimizing Bandwidth, later in this chapter.

The following tables indicate combinations of line modules that allow line rate performance.

Table 5-2 Combinations of line modules for line rate performance - SRP-5G module in an ERX-700 system

Possible combinations of line modules	Examples of allowed combinations	Examples of forbidden combinations
Any combination of supported line modules1 in slot group 1 Any supported line module in slot groups 2, 3, and 4	Two CT1 line modules in slot group 1, one CT3 line module in slot group 2, one T3 line module in slot group 3, and one HSSI line module in slot group 4 One CE1 line module and one E3 line module in slot group 1, one HSSI line module in slot group 2, one FE-2 module in slot group 3, and one E3 line module in slot group 4	A GE/FE line module in any slot group An OCx/STMx ATM line module in any slot group

Table 5-3 Combinations of line modules for line rate performance - SRP-10G module in an ERX-700 system

Possible combinations of line modules	Examples of allowed combinations	Examples of forbidden combinations
One supported line module1 and one empty slot in slot group 1 One OCx/STMx ATM line module and one CE1, CT1, CT3, E3, FE-2, HSSI, T3, or X.21/V.35 line module in slot group 1 Two OCx/STMx ATM line modules in slot group 1 Two CE1, CT1, CT3, E3, FE-2, HSSI, T3, or X.21/V.35 line modules in any combination in slot group 1 One supported line module in slot groups 2, 3 and 4	Two CT1 line modules in slot group 1, one CT3 line module in slot group 2, an OCx/STMx POS line module in slot group 3, and a HSSI line module in slot group 4 One CE1 and one E3 line module in slot group 1, one HSSI line module in slot group 2, one FE-2 module in slot group 3, and one E3 line module in slot group 4	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 5-4 Combinations of line modules for line rate performance - SRP-10G module in an ERX-1400 system 

Possible combinations of line modules	Examples of allowed combinations	Examples of forbidden combinations
One supported line module1 and two empty slots in any slot group One OCx/STMx ATM line module and one or two CE1, CT1, FE-2, or X.21/V.35 line modules in any combination in any slot group One OCx/STMx ATM line module and one CT3, E3, HSSI, or T3 line module and one empty slot in any slot group (bandwidth oversubscription enabled) One OCx/STMx ATM line module and two CT3, E3, HSSI, or T3 line modules in any slot (bandwidth oversubscription disabled) One CT3, E3, HSSI, or T3 line module and two CE1, CT1, FE-2, or X.21/V.35 line modules in any combination in any slot group Two CT3, E3, HSSI, or T3 line modules and one CE1, CT1, FE-2, or X.21/V.35 line module in any combination in any slot group Two CE1, CT1, CT3, E3, FE-2, HSSI, OCx/STMx ATM, T3, or X.21/V.35 line modules in any combination and one empty slot in any slot group Three CE1, CT1, FE-2, or X.21/V.35 line modules in any combination in any slot group	One COCX-F3 line module in slot group 1, a GE/FE line module in slot group 2, three CT1 line modules in slot group 3, and two T3 Frame line modules in slot group 4 Two CE1 line modules and one E3 line modules in slot group 1, two HSSI line modules in slot group 2, an OCx/STMx POS line module in slot group 3, and a GE/FE line module in slot group 4	Three OCx/STMx ATM line modules in any slot group Two GE/FE line modules in any slot group

Table 5-5 Combinations of line modules for line rate performance - SRP-5G+ module in an ERX-705 system

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 module1 and one empty slot in slot group 1 One OCx/STMx ATM line module and one CE1, CT1, CT3, E3, FE-2, HSSI, T3, or X.21/V.35 line module in slot group 1 Two OCx/STMx ATM line modules in slot group 1 Two CE1, CT1, CT3, E3, FE-2, HSSI, T3, or X.21/V.35 line modules in any combination in slot group 1 One CE1, cOCx/STMx, COCX-F3, CT1, CT3, CT3/T3 FO, E3, FE-2, GE/FE, HSSI, IPSec Service, OCx/STMx, T3, or X.21/V.35 line module or one TSM 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, a HSSI line module (0.54 Gbps) in slot group 2, a CT3 3 line module (0.54 Gbps) in slot group 3, and a T3 Frame (0.54 Gbps) line module in slot group 4	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 system.

    bandwidth oversubscription

• Use to enable bandwidth oversubscription for an ERX-700, ERX-705, or ERX-1410 system. Reboot the system after you have issued this command to change the bandwidth oversubscription status.
• By default, bandwidth oversubscription is enabled.
• Example

host1#bandwidth oversubscription

• Use the no version to disable bandwidth oversubscription. Reboot the system after you have issued this command to change the bandwidth oversubscription status.

Monitoring Bandwidth Oversubscription

Use the show bandwidth oversubscription and show utilization (see Monitoring Modules, later in this chapter) commands to monitor the status of bandwidth oversubscription.

    show bandwidth oversubscription

• Use to display the bandwidth oversubscription status for an ERX-700, ERX-705, or ERX-1410 system.
• Example 1: This example shows the display when bandwidth oversubscription is enabled.

host1#show bandwidth oversubscription

Bandwidth oversubscription is currently in effect.

• Example 2: This example shows the display that appears after you issue the no bandwidth oversubscription command to disable bandwidth oversubscription.

host1#no bandwidth oversubscription

host1#show bandwidth oversubscription

Bandwidth oversubscription is currently in effect.

Bandwidth oversubscription will not be in effect the next 
time the system reboots.

• Example 3: This example shows the display when bandwidth oversubscription is disabled.

host1#show bandwidth oversubscription

Bandwidth oversubscription is currently not in effect.

• Example 4: This example shows the display that appears after you issue the bandwidth oversubscription command to enable bandwidth oversubscription.

host1#bandwidth oversubscription

host1#show bandwidth oversubscription

Bandwidth oversubscription is currently not in effect.

Bandwidth oversubscription will be in effect the next time 
the system reboots.

Troubleshooting

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 system 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 over subscribed at slot 0-2

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

Optimizing Bandwidth

If you change line modules in a quadrant that contains FE-2 line modules, issue the reload slot command on the slots that contain the FE-2 line modules. This action optimizes the bandwidth in the quadrant. If you do not optimize the bandwidth, the line modules in the quadrant may not operate at the optimal rate or may be disabled.

If a line module is disabled because of insufficient bandwidth, when you issue the show version commands, the description "disabled (cfg error)" appears in the display for the affected modules. In addition, depending on the log configuration, the following message may appear on the console:

Line card in slot xx is disabled because of lack of fabric 
bandwidth in the quadrant