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Table Of Contents
Input Translation Table Management Enhancements
Related Features and Technologies
Supported Standards, MIBs, and RFCs
Specifying a Minimum Block Size
Verifying Minimum ITT Block Size
Enabling Automatic Determination of Minimum ITT Block Size
Verifying Automatic Determination of Minimum ITT Block Size
Reclaiming ITT Space Dynamically
Verifying Automatic Shrinking of ITT Blocks
Monitoring and Maintaining ITT
Enable Automatic Analysis of Minimum ITT B lock Size
Enable Automatic Shrinking of ITT Blocks
atm input-xlate-table autominblock
atm input-xlate-table autoshrink
atm input-xlate-table minblock
Input Translation Table Management Enhancements
This feature module describes the software enhancements that provide alternatives in managing the Input Translation Table (ITT) resource in the Cisco 6400 series Node Switch Processor (NSP) and includes the following sections:
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Supported Standards, MIBs, and RFCs
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Feature Overview
This software feature adds three enhancements that display and alter switch behavior in managing the ITT resource.
The ITT:
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The Node Switch Processor (NSP) has a single ITT, organized in two banks of 32K entries each. When a VC is created, a block of entries is allocated in the ITT for that VPI. The block size should be a power two that is greater than or equal to the VCI value. This limits the use of large VCI values and the distribution of VCIs on VPIs as the number of VCs approaches 32K. When an additional VC is added to a VPI that requires a larger block size than the current block, the current block is copied to new larger block, and the original block is freed. This leaves a series of small blocks that are unused. ITT memory is fragmented because of this growing technique.
The Cisco 6400 series has three new features to:
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New configuration commands to minimize fragmentation enable the NSP to automatically determine the minimum ITT block size needed to support the PVCs configured for each interface and VPI. When an interface comes up, the minblock command specifies the ITT block size requested for a VPI on that interface.
By default, the ITT blocks grow as necessary to accommodate high VCI values for a given port and VPI, but ITT space is not returned unless the entire ITT block is free. A new command is introduced that reduces the size of an ITT block when a VC with a high numbered VCI is deleted.
A command to display details of the used and unused ITT blocks is also introduced. This gives a picture of the quantity and quality of ITT utilization at a given time. The output of the show command allows you to view details of the free blocks by size and bank, the aggregate free space left, and the location of in-use blocks.
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Benefits
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Restrictions
This feature is supported only on the Cisco IOS Release 12.1(4)DB and later releases on the
Cisco 6400 series.
Related Features and Technologies
None
Related Documents
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Supported Platforms
The ITT Management Enhancements feature is supported on the Cisco 6400 NSP.
Supported Standards, MIBs, and RFCs
None
Prerequisites
None
Configuration Tasks
See the following sections for Cisco 6400 NSP configuration tasks:
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Specifying a Minimum Block Size
If you know the highest VCI that will be required for a particular interface and VPI combination, you can specify it as the minimum ITT block size for that combination. Specifying a minimum block size reduces fragmentation by preventing block expansion. Use the force keyword to ensure that the block size is not overidden by the autominblock analysis.
To specify a minimum block size for a particular interface and VPI, complete the following steps beginning in global configuration mode:
Verifying Minimum ITT Block Size
To verify that you successfully configured minimum ITT block size for an interface and VPI, use the more system:running-config EXEC command. Observe the block size for each interface and VPI using the show atm-input-xlate-table inuse command.
Enabling Automatic Determination of Minimum ITT Block Size
The NSP can automatically determine the optimal ITT block size for every configured interface and VPI. Based on the analysis of PVCs and Soft PVCs, it can insert minblock commands for each interface and VPI combination.
To enable the automatic analysis and determination of minimum block size, use the following command in global configuration mode:
Switch(config)# atm input-xlate-table autominblock
Enables the automatic determination of minimum block size for each interface and VPI combination.
Verifying Automatic Determination of Minimum ITT Block Size
To verify that you successfully enabled autominblock command, use the
more system:running-config EXEC command. Observe that the output includes
atm input-xlate-table autominblock command in the running configuration.Reclaiming ITT Space Dynamically
When high numbered VCs are deleted from the configuration, it is possible to shrink the corresponding ITT block in place and release the unused ITT resources . To enable automatic shrinking of ITT blocks, use the following command in global configuration mode:
Switch(config)# atm input-xlate-table autoshrink
Enables the automatic shrinking of ITT blocks inplace when high numbered VCs are deleted.
Verifying Automatic Shrinking of ITT Blocks
To verify that you successfully enabled the autoshrink command, use the
more system:running-config EXEC command. Observe the block size using the
show atm input-xlate-table inuse command.Troubleshooting Tips
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Monitoring and Maintaining ITT
The EXEC mode command show atm input-xlate-table allows you to view a comprehensive picture of ITT utilization, including the blocks that are used and available and the ports where the blocks are allocated. The output of the command shows details of the free blocks by size and bank, the aggregate free space left, and the location of in-use blocks. When you use the show command with the inuse keyword, the output of the command shows a detailed list of in-use blocks by port and VPI to which they are dedicated.
Configuration Examples
This section provides the following configuration examples:
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Specify Minimum Block Size
The following example shows how to specify minimum block size for VPIs on an interface by manual configuration:
!interface atm 1/0/0atm input-xlate-table minblock vpi 0 1024 forceatm input-xlate-table minblock vpi 1 2048 forceatm input-xlate-table minblock vpi 4 1024 forceexit!Enable Automatic Analysis of Minimum ITT B lock Size
The following example shows how to enable automatic analysis of minimum ITT block requirements for each VPI on an interface when generating a startup configuration file:
!atm input-xlate-table autominblock!Enable Automatic Shrinking of ITT Blocks
The following example shows how to shrink an ITT block in place and release the unwanted ITT resources when high numbered VCs are deleted from the configuration:
!atm input-xlate-table autoshrinkinterface atm 1/0/0no atm pvc 0 1010no atm pvc 0 1011exitno atm input-xlate-table autoshrink!Command Reference
This section documents three new configuration mode commands and one new exec mode command. All other commands used with this feature are documented in the Cisco IOS Release 12.1 command reference publications and ATM Switch Router Command Reference publication.
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atm input-xlate-table autominblock
To enable automatic determination of minimum Input Translation Table block sizes for all virtual path identifiers (VPI's) populated with permanent virtual circuits (PVC's) and Soft PVC source legs, use the
atm input-xlate-table autominblock global configuration mode command. To disable autominblock mode, use the no form of this command.atm input-xlate-table autominblock
no atm input-xlate-table autominblock
Syntax Description
This command has no arguments or keywords.
Defaults
Autominblock mode is disabled.
Command Modes
Global configuration mode
Command History
Usage Guidelines
When you enable the autominblock mode on a Node Switch Processor (NSP), the system analyzes all interfaces and determines minimum ITT block sizes for all VPIs populated with PVCs and Soft PVC source legs that can use the ITT ( but a point to-multipoint leaf would not be included). The autominblock mode also updates the analysis when virtual circuits (VC's) are added or deleted. If you generate the configuration command-line interface (CLI), for example, by using the more system:running-config command, minblock commands are inserted as appropriate for all VPIs populated with PVCs on all external ATM interfaces.
You can specify a minimum block size for an interface and VPI combination by using the force keyword, even when the autominblock command is enabled. See the following table for the effect of minblock commands in different situations:
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Similarly, autominblock mode does not eliminate fragmentation generated as a result of VCs configured after the autominblock mode is enabled, but ensures that the software allocates optimal-size blocks on interface flaps subsequent to the definition of a PVC with a maximum VCI.
To ensure that the software subsequently allocates optimal-sized ITT blocks—even after you restart the system—enable the autominblock mode before or after all PVCs are defined. Save the configuration by using the copy running-config startup-config command.
You do not need to set up a cross-connect to specify a minimum block through autominblock analysis. Because autominblock analysis considers PVC half legs, you can use these half legs to establish the maximum intended virtual channel identifier (VCI) range, which helps to eliminate the growth of ITT block sizes in the future.
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The system analyzes the ITT needs of VP tunnel subinterfaces and configures the parent physical interface accordingly. Enabling this command mode increases the use of processor and memory resources.
Examples
The following example shows how to enable autominblock mode:
!atm input-xlate-table autominblock!Related Commands
atm input-xlate-table minblock
Specifies the minimum ITT block size for a specific VPI on an interface.
atm input-xlate-table autoshrink
To shrink the existing Input Translation Table (ITT) blocks in-place when high numbered virtual circuits (VC's) are deleted, use the atm input-xlate-table autoshrink configuration mode command. To disable autoshrink, use the no form of this command.
atm input-xlate-table autoshrink
no atm input-xlate-table autoshrink
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled.
Command Modes
Global configuration mode
Command History
Usage Guidelines
Be careful when enabling this command mode, because it increases the use of processor and memory resources.
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Examples
The following example shows how to shrink an ITT block in place and release the unrequired ITT resources when high numbered VCs are deleted from the configuration:
!atm input-xlate-table autoshrink!
interface atm 1/0/0
no atm pvc 0 1010no atm pvc 0 1011exit!no atm input-xlate-table autoshrinkRelated Commands
atm input-xlate-table minblock
To specify the minimum Input Translation Table (ITT) block size for a specific virtual path identifier (VPI) on an interface, use the atm input-xlate-table minblock interface configuration mode command. To remove the minimum block size specification, use the no form of this command.
atm input-xlate-table minblock vpi vpi- value blocksize force
no atm input-xlate-table minblock vpi vpi-value
Syntax Description
Defaults
No minimum block size is specified.
Command Modes
Interface configuration mode
Command History
Usage Guidelines
Ensure that the block size you specify corresponds to the desired virtual circuit (VC) usage, so that the system resource is not overused. ITT resource is used only when a connection is installed (when both interfaces that the VC transits are up).
This command is particularly useful when you anticipate the needs of switched virtual circuits (SVC's) transiting an interface and VPI, and you want to avoid the fragmentation associated with ITT growth. If the initial ITT block allocation fails and the actual block size needed [to accomodate a specific virtual channel identifier (VCI) ] is less than the specified minimum block size, the software retries the allocation by using the actual size.
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Examples
The following example shows how to specify minimum block size for VPIs on an interface by manual configuration:
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interface atm 1/0/0
atm input-xlate-table minblock vpi 0 1024 forceatm input-xlate-table minblock vpi 1 2048 forceatm input-xlate-table minblock vpi 4 1024 forceexit!Related Commands
atm input-xlate-table autominblock
Automatically determines the minimum ITT block size needed for each VPI that is populated by PVCand Soft PVC source legs.
show atm input-xlate-table
To view the Input Translation Table utilization details, use the show atm input-xlate table command in EXEC mode.
show atm input-xlate table [inuse]
Syntax Description
Defaults
No default behavior or values.
Command Modes
EXEC
Command History
Examples
The following example shows how to use the command to view the ITT utilization details—with and without the inuse keyword:
Switch>show atm input-xlate-tableInput Translation Table Free Blocks:Block-start Size Bank1 1 02 2 04 4 08 8 016 16 032 32 064 64 017408 64 0128 128 017536 128 0256 256 017664 256 0512 512 017920 512 01024 1024 02048 2048 018432 2048 04096 4096 020480 4096 08192 8192 024576 8192 032769 1 132770 2 132772 4 132776 8 132784 16 132800 32 149248 32 132832 64 149152 64 149344 64 132896 128 133024 256 149408 256 133280 512 149664 512 133792 1024 150176 1024 134816 2048 151200 2048 136864 4096 153248 4096 140960 8192 157344 8192 1Input Translation Table Total Free = 64350Input Translation Table In Use (display combines contiguous blocks):Inuse-start Inuse-end Size0 0 116384 17407 102417472 17535 6432768 32768 149216 49247 3249280 49343 64The output of the command with the inuse keyword is:
Switch>show atm input-xlate-table inuseInterface VPI VP/VC Address Size
ATM0/1/0 0 VC 17472 64
ATM0/1/0 2 VP 32768 1
ATM0/1/2 0 VC 49216 32
ATM0/1/2 2 VP 0 1
ATM1/0/0 0 VC 49280 64
ATM1/0/0 9 VC 16384 1024
Related Commands
Glossary
ATM—Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and TI.
ITT—Input Translation Table. A hardware data structure that is used in the Cisco 6400 series to handle the incoming cells.
NSP—Node Switch Processor. The main system processor card in the Cisco 6400 series, residing in chassis slot 0A or 0B. The NSP ATM switch engine and processor and most memory components. The NSP runs the system software, which maintains and executes the management functions that control the system.
PVC—permanent virtual circuit or connection. Virtual circuit that is permanently established. PVCs save bandwidth associated with circuit establishment and tear down in situations where certain virtual circuits must exist all the time. In ATM terminology, called a permanent virtual connection. Compare with SVC. See also virtual circuit.
SoftPVC—Soft PVCs are a hybrid between switched and permanent connections. Soft PVCs are specified by source and destination VPI/VCI values and the destination ATM address. They are then set up through signaling but, unlike SVCs, remain up until manually torn down.
subinterface—One of a number of virtual interfaces on a single physical interface.
SVC—switched virtual circuit. Virtual circuit that is dynamically established on demand and is torn down when transmission is complete. SVCs are used in situations where data transmission is sporadic. Called a switched virtual connection in ATM terminology. Compare with PVC.
VC—Logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (PVC) or switched (SVC). Virtual circuits are used in Frame Relay and X.25. In ATM, a virtual circuit is called a virtual channel. Sometimes abbreviated VC. See also PVC, SVC, VCD, virtual route, and VPI.
VCC—virtual channel connection. Logical circuit, made up of VCLs, that carries data between two end points in an ATM network. Sometimes called a virtual circuit connection. See also VCD, VCL, and VPI.
VCD—virtual circuit descriptor.
VCI—virtual channel identifier. 16-bit field in the header of an ATM cell. The VCI, together with the VPI, is used to identify the next destination of a cell as it passes through a series of ATM switches on its way to its destination. ATM switches use the VPI/VCI fields to identify the next network VCL that a cell needs to transit on its way to its final destination. The function of the VCI is similar to that of the DLCI in Frame Relay. Compare with DLCI. See also VCL and VPI.
VCL—virtual channel link. Connection between two ATM devices. A VCC is made up of one or more VCLs. See also VCC.
VP—Logical grouping of virtual circuits that connect two sites. See also virtual circuit.
VPC—virtual path connection. Grouping of VCCs that share one or more contiguous VPL. See also VCC and VPL.
VPI—virtual path identifier. Eight-bit field in the header of an ATM cell. The VPI, together with the VCI, is used to identify the next destination of a cell as it passes through a series of ATM switches on its way to its destination. ATM switches use the VPI/VCI fields to identify the next VCL that a cell needs to transit on its way to its final destination. The function of the VPI is similar to that of the DLCI in Frame Relay. Compare with DLCI. See also VCD and VCL.
VPL—virtual path link. Within a virtual path, a group of unidirectional VCLs with the same end points. Grouping VCLs into VPLs reduces the number of connections to be managed, thereby decreasing network control overhead and cost. A VPC is made up of one or more VPLs.
