- 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
-
- 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 and Queue Guaranteed Minimum Bandwidth
You can set a guaranteed minimum bandwidth for individual forwarding classes (queues) and for groups of forwarding classes called forwarding class sets (priority groups). Setting a minimum guaranteed bandwidth ensures that priority groups and queues receive the bandwidth required to support the expected traffic.
Guaranteeing Bandwidth Using Hierarchical Scheduling
The guaranteed-rate value for the priority group (configured in a traffic control profile) defines the minimum amount of bandwidth allocated to a forwarding class set on a port, whereas the transmit-rate value of the queue (configured in a scheduler) defines the minimum amount of bandwidth allocated to a particular queue in a priority group. The queue bandwidth is a portion of the priority group bandwidth.
You cannot configure a minimum guaranteed bandwidth (transmit rate) for a forwarding class that is mapped to a strict-high priority queue, and you cannot configure a minimum guaranteed bandwidth (guaranteed rate) for a priority group that includes strict-high priority queues.
Figure 1 shows how the total port bandwidth is allocated to priority groups (forwarding class sets) based on the guaranteed rate of each priority group. It also shows how the guaranteed bandwidth of each priority group is allocated to the queues in the priority group based on the transmit rate of each queue.
The sum of the priority group guaranteed rates cannot exceed the total port bandwidth. If you configure guaranteed rates whose sum exceeds the port bandwidth, the system sends a syslog message to notify you that the configuration is not valid. However, the system does not perform a commit check. If you commit a configuration in which the sum of the guaranteed rates exceeds the port bandwidth, the hierarchical scheduler behaves unpredictably.
The sum of the queue transmit rates cannot exceed the total guaranteed rate of the priority group to which the queues belong. If you configure transmit rates whose sum exceeds the priority group guaranteed rate, the commit check fails and the system rejects the configuration.
You must set both the priority group guaranteed-rate value and the queue transmit-rate value in order to configure
the minimum bandwidth for individual queues. If you set the transmit-rate value but do not set the guaranteed-rate value, the configuration
fails.
You can set the guaranteed-rate value for a priority
group without setting the transmit-rate value for individual
queues in the priority group. However, queues that do not have a configured transmit-rate value can become starved for bandwidth if other
higher-priority queues need the priority group’s bandwidth.
To avoid starving a queue, it is a good practice to configure a transmit-rate value for most queues.
If you configure the guaranteed rate of a priority group as a percentage, configure all of the transmit rates associated with that priority group as percentages. In this case, if any of the transmit rates are configured as absolute values instead of percentages, the configuration is not valid and the system sends a syslog message.
Priority Group Guaranteed Rate (Guaranteed Minimum Bandwidth)
Setting a priority group (forwarding class set) guaranteed-rate enables you to reserve a portion of the port bandwidth for the forwarding
classes (queues) in that forwarding class set. The minimum bandwidth
(guaranteed-rate) that you configure for a priority group
sets the minimum bandwidth available to all of the forwarding classes
in the forwarding class set.
The combined guaranteed-rate value of all of the
forwarding class sets associated with an interface cannot exceed the
amount of bandwidth available on that interface.
You configure the priority group guaranteed-rate in
the traffic control profile. You cannot apply a traffic control profile
that has a guaranteed rate to a priority group that includes a strict-high
priority queue.
Queue Transmit Rate (Guaranteed Minimum Bandwidth)
Setting a queue (forwarding class) transmit-rate enables
you to reserve a portion of the priority group bandwidth for the individual
queue. For example, a queue that handles Fibre Channel over Ethernet
(FCoE) traffic might require a minimum rate of 4 Gbps to ensure the class of service that storage area network (SAN)
traffic requires.
The priority group guaranteed-rate sets the aggregate
minimum amount of bandwidth available to the queues that belong to
the priority group. The cumulative total minimum bandwidth the queues
consume cannot exceed the minimum bandwidth allocated to the priority
group to which they belong. (The combined transmit rates of the queues
in a priority group cannot exceed the priority group’s guaranteed
rate.)
You must configure the guaranteed-rate value of the
priority group in order to set a transmit-rate value for
individual queues that belong to the priority group. The reason is
that if there is no guaranteed bandwidth for a priority group, there
is no way to guarantee bandwidth for queues in that priority group.
You configure the queue transmit-rate in the scheduler
configuration. You cannot configure a transmit rate for a strict-high
priority queue.
