ATM Policing by Service Category for SVC SoftPVC

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When configured, an ATM switch at the network side of a user-to-network (UNI) interface polices the flow of cells in the forward (into the network) direction of a virtual connection. These traffic policing mechanisms are known as usage parameter control (UPC). With UPC, the switch determines whether received cells comply with the negotiated traffic management values and takes one of the following actions on violating cells:

• Pass the cell without changing the cell loss priority (CLP) bit in the cell header.
• Tag the cell with a CLP bit value of 1.
• Drop (discard) the cell.

This feature enables you to select which traffic is affected by UPC and how it is affected. For example, you can configure your switch to pass all UBR traffic, but tag all other traffic types.

For more information about UPC, see the "Traffic and Resource Management" chapter in the Guide to ATM Technology .

• Configuring ATM Policing by Service Category
• Verifying ATM Policing by Service Category
• Troubleshooting Tips

Switch# show atm vc int atm 0/0/1 2 120
Interface:ATM0/0/1, Type:oc3suni 
VPI = 2  VCI = 120
Status:DOWN
Time-since-last-status-change:1w1d
Connection-type:PVC 
Cast-type:point-to-multipoint-leaf
Packet-discard-option:disabled
Usage-Parameter-Control (UPC):pass
 
Wrr weight:2
Number of OAM-configured connections:0
OAM-configuration:disabled
OAM-states: Not-applicable
Cross-connect-interface:ATM0/0/1, Type:oc3suni 
...

Switch# show atm interface atm 8/0/1
Interface:     ATM8/0/1        Port-type:     oc3suni
IF Status:     UP              Admin Status:  up
Auto-config:   enabled         AutoCfgState:  completed
IF-Side:       Network         IF-type:       NNI
Uni-type:      not applicable  Uni-version:   not applicable
Max-VPI-bits:  8               Max-VCI-bits:  14
Max-VP:        255             Max-VC:        16383
ConfMaxSvpcVpi:255             CurrMaxSvpcVpi:255
ConfMaxSvccVpi:255             CurrMaxSvccVpi:255
ConfMinSvccVci:35              CurrMinSvccVci:35
Svc Upc Intent:by sc
           Signalling:    Enabled
ATM Address for Soft VC:47.0091.8100.0000.0002.b9ae.9301.4000.0c84.0010.00
Configured virtual links:
  PVCLs SoftVCLs   SVCLs   TVCLs   PVPLs SoftVPLs   SVPLs Total-Cfgd Inst-Conns
      3        4       0       0       1        0       0          8          7
Logical ports(VP-tunnels):    0
Input cells:   3036674         Output cells:  3036816
5 minute input rate:            0 bits/sec,       0 cells/sec
5 minute output rate:           0 bits/sec,       0 cells/sec
Input AAL5 pkts:1982638, Output AAL5 pkts:1982687, AAL5 crc errors:0

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    Router# show atm interface

4.    Router# show controllers atmslot/subslot/port

5.    Router# show atm vc [interface atmslot/subslot/port ]

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	Router# show atm interface	Displays ATM-specific information about an ATM interface.
Step 4	Router# show controllers atmslot/subslot/port	Displays information about a physical port device. Includes dropped (or discarded) cells.
Step 5	Router# show atm vc [interface atmslot/subslot/port ]	Displays the configured UPC action and intelligent packet discard mechanisms, as well as the number of cells discarded because of UPC violations.

• Non-UBR Traffic Policing Example
• Monitoring and Maintaining ATM Policing by Service Category Example

Router(config)# interface atm 3/0/0
Router(config-if)# atm svc-upc-intent ubr pass
Router(config-if)# atm svc-upc-intent cbr tag
Router(config-if)# atm svc-upc-intent vbr-rt tag
Router(config-if)# atm svc-upc-intent vbr-nrt tag
Router(config-if)# atm svc-upc-intent abr drop

Switch# show atm vc interface atm 3/0/1.51 51 16
 
     Interface: ATM3/0/1.51, Type: oc3suni 
     VPI = 51  VCI = 16 
     Status: DOWN 
     Time-since-last-status-change: 2w0d 
     Connection-type: PVC 
     Cast-type: point-to-point 
     Packet-discard-option: enabled
 
     Usage-Parameter-Control (UPC): pass
 
     Wrr weight: 32 
     Number of OAM-configured connections: 0 
     OAM-configuration: disabled 
     OAM-states:  Not-applicable 
     Cross-connect-interface: ATM2/0/0, Type: ATM Swi/Proc 
     Cross-connect-VPI = 0 
     Cross-connect-VCI = 73 
     Cross-connect-UPC: pass 
     Cross-connect OAM-configuration: disabled 
     Cross-connect OAM-state:  Not-applicable 
     Encapsulation: AAL5ILMI 
     Threshold Group: 6, Cells queued: 0 
     Rx cells: 0, Tx cells: 0 
     Tx Clp0:0,  Tx Clp1: 0 
     Rx Clp0:0,  Rx Clp1: 0 
     Rx Upc Violations:0, Rx cell drops:0
 
     Rx pkts:0, Rx pkt drops:0 
     Rx connection-traffic-table-index: 6 
     Rx service-category: UBR (Unspecified Bit Rate) 
     Rx pcr-clp01: 424 
     Rx scr-clp01: none 
     Rx mcr-clp01: none 
     Rx      cdvt: 1024 (from default for interface) 
     Rx       mbs: none 
     Tx connection-traffic-table-index: 6 
     Tx service-category: UBR (Unspecified Bit Rate) 
     Tx pcr-clp01: 424 
     Tx scr-clp01: none 
     Tx mcr-clp01: none 
     Tx      cdvt: none 
     Tx       mbs: none 
     No AAL5 connection registered

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Asynchronous Transfer Mode Command Reference. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.

• atm svc-upc-intent

ABR --available bit rate. QoS class defined by the ATM Forum for ATM networks. ABR is used for connections that do not require timing relationships between source and destination. ABR provides no guarantees in terms of cell loss or delay, providing only best-effort service. Traffic sources adjust their transmission rate in response to information they receive describing the status of the network and its capability to successfully deliver data. Compare with CBR, UBR, and VBR.

CBR --constant bit rate. QoS class defined by the ATM Forum for ATM networks. CBR is used for connections that depend on precise clocking to ensure undistorted delivery. Compare with ABR, UBR, and VBR.

CLP --cell loss priority. Field in the ATM cell header that determines the probability of a cell being dropped if the network becomes congested. Cells with CLP = 0 are insured traffic, which is unlikely to be dropped. Cells with CLP = 1 are best-effort traffic, which might be dropped in congested conditions to free up resources to handle insured traffic.

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.

soft PVC --A PVC-SVC hybrid in which only the two terminating virtual connection links (VCLs) at either end are permanent and the rest of the VCLs are switched (SVC). Like the PVC, a soft PVC is permanent and the called party cannot drop the connection. Like the SVC, a soft PVC is automatically rerouted if a switch or link in the path fails.

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. See also virtual circuit. Called a switched virtual connection in ATM terminology. Compare with PVC.

tagged traffic --ATM cells that have their CLP bit set to 1. If the network is congested, tagged traffic can be dropped to ensure the delivery of higher-priority traffic. Sometimes called DE traffic. See also CLP.

traffic policing --Process used to measure the actual traffic flow across a given connection and compare it to the total admissible traffic flow for that connection. Traffic outside of the agreed upon flow can be tagged (where the CLP bit is set to 1) and can be discarded en route if congestion develops. Traffic policing is used in ATM, Frame Relay, and other types of networks. Also known as admission control, permit processing, rate enforcement, and UPC. See also tagged traffic.

UBR --unspecified bit rate. QoS class defined by the ATM Forum for ATM networks. UBR allows any amount of data up to a specified maximum to be sent across the network but there are no guarantees in terms of cell loss rate and delay. Compare with ABR, CBR, and VBR.

UPC --usage parameter control. See traffic policing.

VBR --variable bit rate. QoS class defined by the ATM Forum for ATM networks. VBR is subdivided into a real time (RT) class and non-real time (NRT) class. VBR (RT) is used for connections in which there is a fixed timing relationship between samples. VBR (NRT) is used for connections in which there is no fixed timing relationship between samples but that still need a guaranteed QoS. Compare with ABR, CBR, and UBR.

virtual circuit --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.