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Hierarchical Class of Service in ACX Series Routers

Scheduling properties can be applied at both physical as well as logical interface levels. Service providers will be able to support hierarchical class of service (HCoS) at multiple levels to meet the service level agreements and bandwidth allocations for subscribers.

Hierarchical Scheduling on the Physical Interface

By default, the queuing mode on all the physical interfaces in ACX routers that support HCoS is 8 queues per physical interface (port). In the hierarchical scheduler mode, you can configure up to 3 levels (physical interface, logical interface, and queues) or 4 levels (including logical interfaces sets) of scheduling, depending on the platform.

You can enable hierarchical scheduling by including the hierarchical-scheduler CLI command under the [edit interfaces interface-name] hierarchy:

Note:

If you change the physical interface queuing mode from default to hierarchical scheduler mode or vice-versa, the traffic flowing out of the physical interface during the mode change results in a transient loss of traffic data.

Traffic Control Profiles

The traffic control profiles hold parameters for levels above the queue level of the scheduler hierarchy. The scheduling and shaping configuration on the scheduler nodes are configured using traffic-control-profiles CLI command and scheduler is for queue level. The traffic control profile defines the following characteristics of a scheduler node:

  • Scheduler-map

  • Shaping rate

  • Guaranteed rate

Traffic control profiles can be attached at physical interface and logical interface level. Scheduling and shaping characteristics can be defined for the scheduler node using shaping-rate and guaranteed-rate. The following is a sample traffic control profile configuration:

Schedulers

A scheduler defines scheduling and queuing characteristics of a queue and holds the information about the queues, the last level of the hierarchy. The following is a sample scheduler configuration:

Note:

We do not support transmit-rate with priority queues on ACX Series routers.

Deep Buffer Control

With deep buffer control, also known as fine-grained buffer control, you can configure buffers on a per-queue basis.

On ACX routers running Junos OS Evolved, by default all queues on HQoS enabled logical interfaces have a dedicated buffer of 4KB and a shared buffer of 10msec. Table 1 and Table 2 show the guaranteed and shared per queue default buffers on ACX routers running Junos OS Evolved.

Table 1: Guaranteed Buffer per Queue on HCoS-enabled Physical Ports

Interface Speed (GB)

Minimum Guaranteed Buffer (KB)

1/10

125

25/40/50

625

100

1250

200

2500

400

5000

Table 2: Shared Buffer per Queue on HCoS-enabled Physical Ports

Interface Speed (GB)

Shared buffer size (MB)

Shared buffer size (ms)

1

5

40

10

50

40

25

250

80

40

250

50

50

250

40

100

500

40

200

500

20

400

500

10

You can configure the shared and guaranteed buffers for each queue on HCoS-enabled ports and logical interfaces. See buffer-size (Schedulers).

Note:

Use the temporal option to configure shared buffers.

Drop Profiles

Drop profiles allow you to specify queue specific behavior to drop packets based on WRED profile under congestion. The following is a sample drop profile configuration:

Scheduler Maps

A scheduler map is referenced by traffic control profiles to define queues. The scheduler map establishes the number of queues over a scheduler node, associating a forwarding-class with a scheduler. The following is a sample scheduler map configuration:

Applying the Traffic Control Profiles

You can attach the traffic control profiles at various levels of the scheduler hierarchy to achieve hierarchical class of service. The following is a sample configuration to apply traffic control profiles:

Note:

Although a shaping rate can be applied directly to the physical interface, hierarchical schedulers must use a traffic control profile to hold this parameter.

HCoS on Aggregated Ethernet Interfaces

Configuring HCoS on aggregated Ethernet (AE) interfaces is exactly the same as configuring HCoS on physical interfaces. Apply all HCoS configuration to the AE interface.

Note:

You cannot apply HCoS configuration to a physical interface that is a member of an AE interface.

HCoS configuration on an AE interface is automatically applied to each member interface. How the system applies the configuration to each member interfaces (that is, whether the configuration is normalized or not) depends on the AE interface configuration mode:

  • Link protection mode — system applies configuration directly to each member interface without normalization.

  • Non-link protection replica mode — system applies configuration directly to each member interface without normalization.

  • Non-link protection scale mode (default mode) — system does normalize the configuraiton before applying to each member interface.

HCoS configuration has the following requirements when the configuration must be normalized across member interfaces:

  • transmit-rate at scheduler/queue level — both percent and absolute configuration allowed

  • shaping-rate at scheduler/queue level — both percent and absolute configuration allowed

  • guaranteed-rate at traffic control profile level — only absolute configuration allowed

  • shaping-rate at traffic control profile level — only absolute configuration allowed

  • shaping-rate at port level — only absolute configuration allowed

If the configuration must be normalized, rates configured as a percent require no normalization. If the configuration must be normalized, rates configured as absolute must be normalized. You can calculated the normalized value for each interface by deviding the absolute configured value by the number of member interfaces in the AE interface.

Subscriber Services

Supported ACX routers support hierarchical class of service functionality for subscriber services such as Layer 3 VPN, Layer 2 VPN, Ethernet pseudowire (VPWS), and VPLS for logical interface instance on the AC (Access Port).

Note:

Hierarchical class of service is not supported for Layer 2 bridging (bridge domain VLAN) service.

The following sections explain the hierarchical class of service configuration for subscriber services:

Configuring hierarchical class of service for Layer 3 VPN Service

Supported ACX routers can be configured to provide Layer 3 VPN services to subscribers by connecting the UNI port to a CE device. The physical port can be configured to provide Layer 3 VPN services to multiple subscribers. You can schedule traffic for different Layer 3 VPN instances based on the SLA parameters agreed with the subscriber.

The following is a sample UNI and NNI logical interface configuration on the PE router providing the Layer 3 VPN service:

Scheduling can be enabled on the interfaces to achieve hierarchical class of service support for traffic flowing from NNI towards UNI direction.

Configuring hierarchical class of service for Layer 2 VPN (Ethernet Pseudowires) Service

Supported ACX routers can be configured to provide Layer 2 VPN services to subscribers based on Ethernet pseudowires where the UNI port is connected to a CE device. The physical port can be configured to provide Layer 2 VPN services to multiple subscribers. You can schedule traffic for different pseudowires based on the SLA parameters agreed with the subscriber. Hierarchical class of service can be enabled per UNI logical interface represented as the attachment point of the Ethernet pseudowire to achieve the functionality.

The following is a sample to configure the UNI logical interface on the PE router providing the Layer 2 VPN service based on Ethernet pseudowire:

You can enable scheduling on the interfaces to achieve hierarchical class of service for traffic flowing from NNI towards UNI direction.

Configuring hierarchical class of service for VPLS Service

Supported ACX routers can be configured to provide Layer 2 VPN services to subscribers based on VPLS where the UNI port can be connected to a CE device. Subscriber network is attached to UNI logical interface at the PE router and have a VPLS instance. The same physical port can service multiple VPLS instances for various subscribers. The service provider can schedule traffic for different VPLS instances based on the SLA parameters agreed with the subscriber. You can enable hierarchical class of service per UNI logical interface representing the VPLS instance for the subscriber to achieve the functionality.

The following is a sample to configure the UNI logical interface on the PE router providing the VPLS service:

Scheduling can be enabled on the interfaces to achieve hierarchical class of service for the traffic flowing from NNI towards UNI direction.

Verifying the hierarchical class of service configurations

You can use the following CLI commands to verify the configuration:

  • show interfaces queue—Shows physical interface aggregate, physical interface remaining, and logical interface traffic statistics to monitor the traffic received and transmitted. The following are some sample outputs of show interfaces queue CLI command:

  • show class-of-service packet-buffer usage—Shows the total buffer usage of the system. The following is a sample output of the show class-of-service packet-buffer usage CLI command:

You can use the syslog to view the log messages and error reports.