- play_arrow Basic CoS Configuration
- play_arrow CoS Overview
- play_arrow CoS on Interfaces
- play_arrow CoS Code-Point Aliases
- play_arrow CoS Classifiers
- Understanding CoS Classifiers
- Defining CoS BA Classifiers (DSCP, DSCP IPv6, IEEE 802.1p)
- Example: Configuring Classifiers
- Example: Configuring Unicast Classifiers
- Example: Configuring Multidestination (Multicast, Broadcast, DLF) Classifiers
- Understanding Host Inbound Traffic Classification
- Configuring a Global MPLS EXP Classifier
- Monitoring CoS Classifiers
- play_arrow CoS Rewrite Rules
- Understanding CoS Rewrite Rules
- Defining CoS Rewrite Rules
- Understanding Applying CoS Classifiers and Rewrite Rules to Interfaces
- Troubleshooting an Unexpected Rewrite Value
- Understanding CoS MPLS EXP Classifiers and Rewrite Rules
- Configuring Rewrite Rules for MPLS EXP Classifiers
- Monitoring CoS Rewrite Rules
- play_arrow CoS Forwarding Classes and Forwarding Class Sets
- Understanding CoS Forwarding Classes
- Defining CoS Forwarding Classes
- Forwarding Policy Options Overview
- Configuring CoS-Based Forwarding
- Example: Configuring CoS-Based Forwarding
- Example: Configuring Forwarding Classes
- Understanding CoS Forwarding Class Sets (Priority Groups)
- Defining CoS Forwarding Class Sets
- Example: Configuring Forwarding Class Sets
- Monitoring CoS Forwarding Classes
- play_arrow Lossless Traffic Flows, Ethernet PAUSE Flow Control, and PFC
- Understanding CoS IEEE 802.1p Priorities for Lossless Traffic Flows
- Configuring CoS PFC (Congestion Notification Profiles)
- Understanding CoS Flow Control (Ethernet PAUSE and PFC)
- Enabling and Disabling CoS Symmetric Ethernet PAUSE Flow Control
- Configuring CoS Asymmetric Ethernet PAUSE Flow Control
- Understanding PFC Functionality Across Layer 3 Interfaces
- Example: Configuring PFC Across Layer 3 Interfaces
- Understanding PFC Using DSCP at Layer 3 for Untagged Traffic
- Configuring DSCP-based PFC for Layer 3 Untagged Traffic
- play_arrow CoS and Host Outbound Traffic
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- play_arrow Weighted Random Early Detection (WRED) and Explicit Congestion Notification (ECN)
- play_arrow WRED and Drop Profiles
- play_arrow Explicit Congestion Notification (ECN)
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- play_arrow Data Center Bridging and Lossless FCoE
- play_arrow Data Center Bridging
- Understanding DCB Features and Requirements
- Understanding DCBX
- Configuring the DCBX Mode
- Configuring DCBX Autonegotiation
- Understanding DCBX Application Protocol TLV Exchange
- Defining an Application for DCBX Application Protocol TLV Exchange
- Configuring an Application Map for DCBX Application Protocol TLV Exchange
- Applying an Application Map to an Interface for DCBX Application Protocol TLV Exchange
- Example: Configuring DCBX Application Protocol TLV Exchange
- play_arrow Lossless FCoE
- Example: Configuring CoS PFC for FCoE Traffic
- Example: Configuring CoS for FCoE Transit Switch Traffic Across an MC-LAG
- Example: Configuring CoS Using ELS for FCoE Transit Switch Traffic Across an MC-LAG
- Example: Configuring Lossless FCoE Traffic When the Converged Ethernet Network Does Not Use IEEE 802.1p Priority 3 for FCoE Traffic (FCoE Transit Switch)
- Example: Configuring Two or More Lossless FCoE Priorities on the Same FCoE Transit Switch Interface
- Example: Configuring Two or More Lossless FCoE IEEE 802.1p Priorities on Different FCoE Transit Switch Interfaces
- Example: Configuring Lossless IEEE 802.1p Priorities on Ethernet Interfaces for Multiple Applications (FCoE and iSCSI)
- Troubleshooting Dropped FCoE Traffic
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- play_arrow CoS Buffers and the Shared Buffer Pool
- play_arrow CoS Buffers Overview
- play_arrow Shared Buffer Pool Examples
- Example: Recommended Configuration of the Shared Buffer Pool for Networks with Mostly Best-Effort Unicast Traffic
- Example: Recommended Configuration of the Shared Buffer Pool for Networks with Mostly Best-Effort Traffic on Links with Ethernet PAUSE Enabled
- Example: Recommended Configuration of the Shared Buffer Pool for Networks with Mostly Multicast Traffic
- Example: Recommended Configuration of the Shared Buffer Pool for Networks with Mostly Lossless Traffic
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- play_arrow CoS on EVPN VXLANs
- play_arrow Configuration Statements and Operational Commands
Understanding CoS Priority Group Scheduling
Priority group scheduling defines the class-of-service (CoS) properties of a group of output queues (priorities). Priority group scheduling works with output queue scheduling to create a two-tier hierarchical scheduler. The hierarchical scheduler allocates bandwidth to a group of queues (a priority group, called a forwarding class set in Junos OS configuration). Queue scheduling determines the portion of the priority group bandwidth that the particular queue can use.
You configure priority group scheduling in a traffic control profile and then associate the traffic control profile with a forwarding class set and an interface. You attach a scheduler map to the traffic control profile to specify the queue scheduling characteristics.
When you configure bandwidth for a queue or a priority group, the switch considers only the data as the configured bandwidth. The switch does not account for the bandwidth consumed by the preamble and the interframe gap (IFG). Therefore, when you calculate and configure the bandwidth requirements for a queue or for a priority group, consider the preamble and the IFG as well as the data in the calculations.
Priority Group Scheduling Components
Table 1 provides a quick reference to the traffic control profile components you can configure to determine the bandwidth properties of priority groups, and Table 2 provides a quick reference to some related scheduling configuration components.
Traffic Control Profile Component | Description |
|---|---|
Guaranteed rate | Sets the minimum guaranteed port bandwidth for the priority group. Extra port bandwidth is shared among priority groups in proportion to the guaranteed rate of each priority group on the port. |
Shaping rate | Sets the maximum port bandwidth the priority group can consume. |
Scheduler map | Maps schedulers to queues (forwarding classes, also called priorities). This determines the portion of the priority group bandwidth that a queue receives. |
Other Scheduling Components | Description |
|---|---|
Forwarding class | Maps traffic to a queue (priority). |
Forwarding class set | Name of a priority group. You map forwarding classes to priority groups. A forwarding class set consists of one or more forwarding classes. |
Scheduler | Sets the bandwidth and scheduling priority of individual queues (forwarding classes). |
Guaranteed Rate (Minimum Guaranteed Bandwidth)
The guaranteed rate determines the minimum guaranteed bandwidth for each priority group. It also determines how much excess (extra) port bandwidth the priority group can share; each priority group shares extra port bandwidth in proportion to its guaranteed rate. You specify the rate in bits per second as a fixed value such as 3 Mbps or as a percentage of the total port bandwidth.
The minimum transmission bandwidth can exceed the configured rate if additional bandwidth is available from other priority groups on the port. In case of congestion, the configured guaranteed rate is guaranteed for the priority group. This property enables you to ensure that each priority group receives the amount of bandwidth appropriate to its level of service.
Configuring the minimum guaranteed bandwidth (transmit rate) for a forwarding class does not work unless you also configure the minimum guaranteed bandwidth (guaranteed rate) for the forwarding class set in the traffic control profile.
Additionally, the sum of the transmit rates of the queues in a forwarding class set should not exceed the guaranteed rate for the forwarding class set. (You cannot guarantee a minimum bandwidth for the queues that is greater than the minimum bandwidth guaranteed for the entire set of queues.)
You cannot configure a guaranteed rate for forwarding class sets that include strict-high priority queues.
Sharing Extra Bandwidth
Extra bandwidth is available to priority groups when the priority groups do not use the full amount of available port bandwidth. This extra port bandwidth is shared among the priority groups based on the minimum guaranteed bandwidth of each priority group.
For example, Port A has three priority groups: fc-set-1, fc-set-2, and fc-set-3. Fc-set-1 has a guaranteed rate of 2 Gbps, fc-set-2 has a guaranteed rate of 2 Gbps, and fc-set-3 has a guaranteed rate of 4 Gbps. After servicing the minimum guaranteed bandwidth of these priority groups, the port has an extra 2 Gbps of available bandwidth, and all three priority groups have still have packets to forward. The priority groups receive the extra bandwidth in proportion to their guaranteed rates, so fc-set-1 receives an extra 500 Mbps, fc-set-2 receives an extra 500 Mbps, and fc-set-3 receives an extra 1 Gbps.
Shaping Rate (Maximum Bandwidth)
The shaping rate determines the maximum bandwidth the priority group can consume. You specify the rate in bits per second as a fixed value such as 5 Mbps or as a percentage of the total port bandwidth.
The maximum bandwidth for a priority group depends on the total bandwidth available on the port and how much bandwidth the other priority groups on the port consume.
Scheduler Maps
A scheduler map maps schedulers to queues. When you associate a scheduler map with a traffic control profile, then associate the traffic control profile with an interface and a forwarding class set, the scheduling defined by the scheduler map determines the portion of the priority group resources that each individual queue can use.
You can associate up to four user-defined scheduler maps with traffic control profiles.
