ATM Hierarchical Shaping ATM VC into VP Shaping

If a service (or an application) wants to use an ATM network to transport a particular kind of traffic, it must first inform the network about what kind of traffic is to be transported, and the performance requirements of that traffic. The ATM service categories provide a method to relate traffic characteristics and QoS requirements to network behavior. Hierarchical shaping requires that all VCs belonging to a given VP have the same ATM service category. This hierarchy ensures that packets are shaped first at the VC level and then at the VP level. At the interface level, the priority is based on the ATM service category. The service category is determined by the first PVC that is configured under a VP. The priority is in the following order:

1. Constant Bit Rate (CBR)
2. Unspecified Bit Rate (UBR)
3. Variable Bit Rate Non Real-Time (VBR-nRT)
4. Real-time Variable Bit Rate (VBR-RT)

If no service category is specified at the VC level, the default is unshaped UBR. The ATM Hierarchical Shaping feature is supported for the following ATM traffic service categories:

• VBR-nRT
• UBR

For VBR-nRT traffic the output sustainable cell rate (SCR) value that is configured will be taken into account for VC shaping. For UBR traffic, the output peak cell rate (PCR) value that is configured will be taken into account for VC shaping.

The ATM Hierarchical Shaping feature supports over-subscription. Over-subscription occurs when the sum of the configured rate of UBR and VBR PVCs exceeds the line rate.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface atm interface-number [. subinterface-number {mpls | multipoint | point-to-point}]

4.    atm pvp vpi [peak-rate]

5.    pvc vpi / vci

6.    exit

7.    range [range-name] pvc [start-vpi /]start-vci [end-vpi /]end-vci

8.    ubr output-pcr

9.    exit

10.    atm pvp vpi [peak-rate]

11.    pvc vpi / vci

12.    vbr-nrt output-pcr output-scr [output-maxburstsize]

13.    create on-demand

14.    end

15.    show atm pvc

16.    show atm vp

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	interface atm interface-number [. subinterface-number {mpls | multipoint | point-to-point}] Example: Router(config)# interface atm 0/3/2.1 multipoint	Configure an ATM interface and enters subinterface configuration mode.
Step 4	atm pvp vpi [peak-rate] Example: Router(config-subif)# atm pvp 2	Creates a permanent virtual path (PVP) used to multiplex (or bundle) one or more VCs.
Step 5	pvc vpi / vci Example: Router(config-subif)# pvc 2/200	Creates or assigns a name to an ATM PVC and enters ATM virtual circuit configuration mode.
Step 6	exit Example: Router(config-if-atm-vc)# exit	Exits ATM virtual circuit configuration mode and returns to subinterface configuration mode.
Step 7	range [range-name] pvc [start-vpi /]start-vci [end-vpi /]end-vci Example: Router(config-subif)# range range1 pvc 2/100 2/102	Defines a range of ATM PVCs.
Step 8	ubr output-pcr Example: Router(config-if-atm-vc)# ubr 4000	Configures UBR QoS and specifies the output PCR for an ATM PVC, PVC range, switched virtual circuit (SVC), VC class, or VC bundle member.
Step 9	exit Example: Router(config-if-atm-vc)# exit	Exits ATM virtual circuit configuration mode and returns to subinterface configuration mode.
Step 10	atm pvp vpi [peak-rate] Example: Router(config-subif)# atm pvp 3	Creates a PVP used to multiplex (or bundle) one or more VCs.
Step 11	pvc vpi / vci Example: Router(config-subif)# pvc 3/150	Creates or assigns a name to an ATM PVC and enters ATM virtual circuit configuration mode.
Step 12	vbr-nrt output-pcr output-scr [output-maxburstsize] Example: Router(config-if-atm-vc)# vbr-nrt 1000 1000	Configures the VBR-nRT QoS and specifies output PCR, output SCR, and output maximum burst cell size for an ATM PVC, PVC range, SVC, VC class, or VC bundle member.
Step 13	create on-demand Example: Router(config-if-atm-vc)# create on-demand	Configures ATM PVC autoprovisioning, which enables a PVC or range of PVCs to be created automatically on demand.
Step 14	end Example: Router(config-if-atm-vc)# end	Exits ATM virtual circuit configuration mode and returns to privileged EXEC mode.
Step 15	show atm pvc Example: Router# show atm pvc	(Optional) Displays the statistics for all VPs on an interface or for a specific VP.
Step 16	show atm vp Example: Router# show atm vp	(Optional) Displays all ATM PVCs and traffic information.