- play_arrow Overview
- play_arrow Understanding How Class of Service Manages Congestion and Defines Traffic Forwarding Behavior
- Understanding How Class of Service Manages Congestion and Controls Service Levels in the Network
- How CoS Applies to Packet Flow Across a Network
- The Junos OS CoS Components Used to Manage Congestion and Control Service Levels
- Mapping CoS Component Inputs to Outputs
- Default Junos OS CoS Settings
- Packet Flow Through the Junos OS CoS Process Overview
- Configuring Basic Packet Flow Through the Junos OS CoS Process
- Example: Classifying All Traffic from a Remote Device by Configuring Fixed Interface-Based Classification
- Interface Types That Do Not Support Junos OS CoS
-
- play_arrow Configuring Platform-Specific Functionality
- play_arrow Configuring Class of Service on ACX Series Universal Metro Routers
- CoS on ACX Series Routers Features Overview
- Understanding CoS CLI Configuration Statements on ACX Series Routers
- DSCP Propagation and Default CoS on ACX Series Routers
- Configuring CoS on ACX Series Routers
- Classifiers and Rewrite Rules at the Global, Physical, and Logical Interface Levels Overview
- Configuring Classifiers and Rewrite Rules at the Global and Physical Interface Levels
- Applying DSCP and DSCP IPv6 Classifiers on ACX Series Routers
- Schedulers Overview for ACX Series Routers
- Shared and Dedicated Buffer Memory Pools on ACX Series Routers
- CoS for PPP and MLPPP Interfaces on ACX Series Routers
- CoS for NAT Services on ACX Series Routers
- Hierarchical Class of Service in ACX Series Routers
- Storm Control on ACX Series Routers Overview
- play_arrow Configuring Class of Service on MX Series 5G Universal Routing Platforms
- Junos CoS on MX Series 5G Universal Routing Platforms Overview
- CoS Features and Limitations on MX Series Routers
- Configuring and Applying IEEE 802.1ad Classifiers
- Scheduling and Shaping in Hierarchical CoS Queues for Traffic Routed to GRE Tunnels
- Example: Performing Output Scheduling and Shaping in Hierarchical CoS Queues for Traffic Routed to GRE Tunnels
- CoS-Based Interface Counters for IPv4 or IPv6 Aggregate on Layer 2
- Enabling a Timestamp for Ingress and Egress Queue Packets
- play_arrow Configuring Class of Service on PTX Series Packet Transport Routers
- CoS Features and Limitations on PTX Series Routers
- CoS Feature Differences Between PTX Series Packet Transport Routers and T Series Routers
- Understanding Scheduling on PTX Series Routers
- Virtual Output Queues on PTX Series Packet Transport Routers
- Example: Configuring Excess Rate for PTX Series Packet Transport Routers
- Identifying the Source of RED Dropped Packets on PTX Series Routers
- Configuring Queuing and Shaping on Logical Interfaces on PTX Series Routers
- Example: Configuring Queuing and Shaping on Logical Interfaces in PTX Series Packet Transport Routers
- Example: Configuring Strict-Priority Scheduling on a PTX Series Router
- CoS Support on EVPN VXLANs
- Understanding CoS CLI Configuration Statements on PTX Series Routers
- Classification Based on Outer Header of Decapsulation Tunnel
-
- play_arrow Configuring Line Card-Specific and Interface-Specific Functionality
- play_arrow Feature Support of Line Cards and Interfaces
- play_arrow Configuring Class of Service for Tunnels
- play_arrow Configuring Class of Service on Services PICs
- CoS on Services PICs Overview
- Configuring CoS Rules on Services PICs
- Configuring CoS Rule Sets on Services PICs
- Example: Configuring CoS Rules on Services PICs
- Packet Rewriting on Services Interfaces
- Multiservices PIC ToS Translation
- Fragmentation by Forwarding Class Overview
- Configuring Fragmentation by Forwarding Class
- Configuring Drop Timeout Interval for Fragmentation by Forwarding Class
- Example: Configuring Fragmentation by Forwarding Class
- Allocating Excess Bandwidth Among Frame Relay DLCIs on Multiservices PICs
- Configuring Rate Limiting and Sharing of Excess Bandwidth on Multiservices PICs
- play_arrow Configuring Class of Service on IQ and Enhanced IQ (IQE) PICs
- CoS on Enhanced IQ PICs Overview
- Calculation of Expected Traffic on IQE PIC Queues
- Configuring the Junos OS to Support Eight Queues on IQ Interfaces for T Series and M320 Routers
- BA Classifiers and ToS Translation Tables
- Configuring ToS Translation Tables
- Configuring Hierarchical Layer 2 Policers on IQE PICs
- Configuring Excess Bandwidth Sharing on IQE PICs
- Configuring Rate-Limiting Policers for High Priority Low-Latency Queues on IQE PICs
- Applying Scheduler Maps and Shaping Rate to Physical Interfaces on IQ PICs
- Applying Scheduler Maps to Chassis-Level Queues
- play_arrow Configuring Class of Service on Ethernet IQ2 and Enhanced IQ2 PICs
- CoS on Enhanced IQ2 PICs Overview
- CoS Features and Limitations on IQ2 and IQ2E PICs (M Series and T Series)
- Differences Between Gigabit Ethernet IQ and Gigabit Ethernet IQ2 PICs
- Shaping Granularity Values for Enhanced Queuing Hardware
- Ethernet IQ2 PIC RTT Delay Buffer Values
- Configuring BA Classifiers for Bridged Ethernet
- Setting the Number of Egress Queues on IQ2 and Enhanced IQ2 PICs
- Configuring the Number of Schedulers per Port for Ethernet IQ2 PICs
- Applying Scheduler Maps to Chassis-Level Queues
- CoS for L2TP Tunnels on Ethernet Interface Overview
- Configuring CoS for L2TP Tunnels on Ethernet Interfaces
- Configuring LNS CoS for Link Redundancy
- Example: Configuring L2TP LNS CoS Support for Link Redundancy
- Configuring Shaping on 10-Gigabit Ethernet IQ2 PICs
- Configuring Per-Unit Scheduling for GRE Tunnels Using IQ2 and IQ2E PICs
- Understanding Burst Size Configuration on IQ2 and IQ2E Interfaces
- Configuring Burst Size for Shapers on IQ2 and IQ2E Interfaces
- Configuring a CIR and a PIR on Ethernet IQ2 Interfaces
- Example: Configuring Shared Resources on Ethernet IQ2 Interfaces
- Configuring and Applying IEEE 802.1ad Classifiers
- Configuring Rate Limits to Protect Lower Queues on IQ2 and Enhanced IQ2 PICs
- Simple Filters Overview
- Configuring a Simple Filter
- play_arrow Configuring Class of Service on 10-Gigabit Ethernet LAN/WAN PICs with SFP+
- CoS on 10-Gigabit Ethernet LAN/WAN PIC with SFP+ Overview
- BA and Fixed Classification on 10-Gigabit Ethernet LAN/WAN PIC with SFP+ Overview
- DSCP Rewrite for the 10-Gigabit Ethernet LAN/WAN PIC with SFP+
- Configuring DSCP Rewrite for the 10-Gigabit Ethernet LAN/WAN PIC
- Queuing on 10-Gigabit Ethernet LAN/WAN PICs Properties
- Mapping Forwarding Classes to CoS Queues on 10-Gigabit Ethernet LAN/WAN PICs
- Scheduling and Shaping on 10-Gigabit Ethernet LAN/WAN PICs Overview
- Example: Configuring Shaping Overhead on 10-Gigabit Ethernet LAN/WAN PICs
- play_arrow Configuring Class of Service on Enhanced Queuing DPCs
- Enhanced Queuing DPC CoS Properties
- Configuring Rate Limits on Enhanced Queuing DPCs
- Configuring WRED on Enhanced Queuing DPCs
- Configuring MDRR on Enhanced Queuing DPCs
- Configuring Excess Bandwidth Sharing
- Configuring Customer VLAN (Level 3) Shaping on Enhanced Queuing DPCs
- Simple Filters Overview
- Configuring Simple Filters on Enhanced Queuing DPCs
- Configuring a Simple Filter
- play_arrow Configuring Class of Service on MICs, MPCs, and MLCs
- CoS Features and Limitations on MIC and MPC Interfaces
- Dedicated Queue Scaling for CoS Configurations on MIC and MPC Interfaces Overview
- Verifying the Number of Dedicated Queues Configured on MIC and MPC Interfaces
- Scaling of Per-VLAN Queuing on Non-Queuing MPCs
- Increasing Available Bandwidth on Rich-Queuing MPCs by Bypassing the Queuing Chip
- Flexible Queuing Mode
- Multifield Classifier for Ingress Queuing on MX Series Routers with MPC
- Example: Configuring a Filter for Use as an Ingress Queuing Filter
- Ingress Queuing Filter with Policing Functionality
- Ingress Rate Limiting on MX Series Routers with MPCs
- Rate Shaping on MIC and MPC Interfaces
- Per-Priority Shaping on MIC and MPC Interfaces Overview
- Example: Configuring Per-Priority Shaping on MIC and MPC Interfaces
- Configuring Static Shaping Parameters to Account for Overhead in Downstream Traffic Rates
- Example: Configuring Static Shaping Parameters to Account for Overhead in Downstream Traffic Rates
- Traffic Burst Management on MIC and MPC Interfaces Overview
- Understanding Hierarchical Scheduling for MIC and MPC Interfaces
- Configuring Ingress Hierarchical CoS on MIC and MPC Interfaces
- Configuring a CoS Scheduling Policy on Logical Tunnel Interfaces
- Per-Unit Scheduling and Hierarchical Scheduling for MPC Interfaces
- Managing Dedicated and Remaining Queues for Static CoS Configurations on MIC and MPC Interfaces
- Excess Bandwidth Distribution on MIC and MPC Interfaces Overview
- Bandwidth Management for Downstream Traffic in Edge Networks Overview
- Scheduler Delay Buffering on MIC and MPC Interfaces
- Managing Excess Bandwidth Distribution on Static Interfaces on MICs and MPCs
- Drop Profiles on MIC and MPC Interfaces
- Intelligent Oversubscription on MIC and MPC Interfaces Overview
- Jitter Reduction in Hierarchical CoS Queues
- Example: Reducing Jitter in Hierarchical CoS Queues
- CoS on Ethernet Pseudowires in Universal Edge Networks Overview
- CoS Scheduling Policy on Logical Tunnel Interfaces Overview
- Configuring CoS on an Ethernet Pseudowire for Multiservice Edge Networks
- CoS for L2TP LNS Inline Services Overview
- Configuring Static CoS for an L2TP LNS Inline Service
- CoS on Circuit Emulation ATM MICs Overview
- Configuring CoS on Circuit Emulation ATM MICs
- Understanding IEEE 802.1p Inheritance push and swap from a Transparent Tag
- Configuring IEEE 802.1p Inheritance push and swap from the Transparent Tag
- CoS on Application Services Modular Line Card Overview
- play_arrow Configuring Class of Service on Aggregated, Channelized, and Gigabit Ethernet Interfaces
- Limitations on CoS for Aggregated Interfaces
- Policer Support for Aggregated Ethernet Interfaces Overview
- Understanding Schedulers on Aggregated Interfaces
- Examples: Configuring CoS on Aggregated Interfaces
- Hierarchical Schedulers on Aggregated Ethernet Interfaces Overview
- Configuring Hierarchical Schedulers on Aggregated Ethernet Interfaces
- Example: Configuring Scheduling Modes on Aggregated Interfaces
- Enabling VLAN Shaping and Scheduling on Aggregated Interfaces
- Class of Service on demux Interfaces
- Example: Configuring Per-Unit Schedulers for Channelized Interfaces
- Applying Layer 2 Policers to Gigabit Ethernet Interfaces
-
- play_arrow Configuration Statements and Operational Commands
PFC Watchdog
PFC Watchdog Overview
Priority-based flow control (PFC) pause frames are used in lossless Ethernet to pause the link partner from sending packets. These PFC pause frames can propagate through the whole network and can cause the traffic on the PFC streams to halt. Use the PFC watchdog to detect and resolve PFC pause storms.
The PFC watchdog monitors PFC-enabled ports for PFC pause storms. When a PFC-enabled port receives PFC pause frames for an extended period of time and PFC watchdog does not detect flow control frames on that port, PFC watchdog mitigates the situation. It does this by disabling the queue where the PFC pause storm was detected for a configurable length of time called the recovery time. After the recovery time passes, PFC watchdog re-enables the affected queue.
Use Feature Explorer to confirm platform and release support for specific features.
Understanding PFC Watchdog
The PFC watchdog has three functions: detection, mitigation, and restoration.
The PFC watchdog checks the status of PFC queues at regular intervals called polling intervals. If the PFC watchdog finds a PFC queue with a non-zero pause timer, it compares the queue's current transmit counter register to the last recorded value. If the PFC queue has not transmitted any packets since the last polling interval, the PFC watchdog checks if there are any packets in the queue. If there are packets on the queue that are not being transmitted and there are no flow control frames on that port, the PFC watchdog detects a stall condition.
After the PFC watchdog detects a stall condition, it disables the queue where it detected the PFC pause storm for a period of time called the recovery time. During that time, it flushes all packets in the queue and prevents new packets from being added to the queue. The system monitors all packet drops on the PFC queue during the recovery time.
When the recovery time ends, the PFC watchdog collects the ingress drop counters and any other drop counters associated with disabling the PFC queue. The PFC watchdog maintains a count of the packets lost during the last recovery and the total number of lost packets due to PFC mitigation since the device was started. The PFC watchdog then restores the queue and re-enables PFC.
How to Configure PFC Watchdog
Enable PFC Watchdog
PFC watchdog only works for PFC queues. To designate a queue
as a PFC queue, use the flow-control-queue statement with
the queue number:
set class-of-service congestion-notification-profile cnp output ieee-802.1 code-point 011 flow-control-queue 3 set class-of-service congestion-notification-profile cnp output ieee-802.1 code-point 100 flow-control-queue 4
Enable PFC watchdog using the pfc-watchdog statement
at the [edit class-of-service congestion-notification-profile profile-name] hierarchy level:
set class-of-service congestion-notification-profile profile-name pfc-watchdog
Enabling PFC watchdog on the congestion notification profile without configuring other options enables the PFC watchdog with the default values. By default, the polling interval is 100 ms, the detection period is set to 2 (that is, two polling intervals, or 200 ms), and the recovery time is 200 ms. To learn how to configure non-default values, read the following sections.
Detection
The PFC watchdog monitors the PFC-enabled queues periodically
for continuous PFC pause assertion by the downstream device when the
queue is empty. If this occurs, PFC watchdog detects a stall condition.
The system must detect this stall condition within a specified amount
of time. This length of time is determined by how you configure two
statements: poll-interval and detection.
The PFC watchdog checks the status of PFC queues at regular
intervals. Configure this interval in milliseconds using the poll-interval statement. The PFC watchdog checks the status
of the queues once per polling interval. The default interval is 100 ms.
The minimum interval is 100 ms and the maximum is 1000 ms.
set class-of-service congestion-notification-profile profile-name pfc-watchdog poll-interval time
The PFC watchdog must detect stall conditions for at least two
consecutive polling intervals before it determines that a PFC queue
has stalled. Configure the detection statement to control
how many polling intervals the PFC watchdog waits before it mitigates
the stalled traffic. The default is two polling intervals. The maximum
number is 10 polling intervals.
set class-of-service congestion-notification-profile profile-name pfc-watchdog detection number of polling intervals
The total detection time is the length of the polling interval multiplied by the number of polling intervals.
Mitigation
When the PFC watchdog detects that a PFC queue has stalled,
it moves the queue to the mitigation state. Configure the pfc-watchdog-action statement to specify the action that the PFC watchdog takes to mitigate
the traffic congestion. The only option is the drop action. When the
PFC watchdog detects that a PFC queue has stalled, it drops all queued
packets and all newly arriving packets for the stalled PFC queue.
set class-of-service congestion-notification-profile profile-name pfc-watchdog watchdog-action drop
Restoration
Use the recovery statement to configure how long
the PFC watchdog disables the affected queue for before it restores
PFC. The minimum recovery period is 200 ms and the maximum is
10,000 ms.
set class-of-service congestion-notification-profile profile-name pfc-watchdog recovery time
After the recovery time passes, the PFC watchdog re-enables PFC on the affected queues.
Verification
Use the following command to verify you have configured the PFC watchdog correctly:
show class-of-service congestion-notification-profile
Name: cnp, Index: 0
Type: Input
Cable Length: 100
Type: Output
Priority Flow-Control-Queues
011
3
Priority Flow-Control-Queues
100
4
PFC Watchdog : enabled
PFC-action : drop
Polling Interval : 100 ms
Detection Time : 200 ms
Recovery Time : 200 ms
The detection time shown is the polling interval multiplied by the detection period. In this case, the polling interval is 100 ms, so the configured detection time was two.
Monitoring PFC Watchdog
You can view the number of PFC pause storms that have been detected and recovered, as well as the number of packets that have been dropped, on the PFC queues on an interface. Use the following command to view the PFC watchdog statistics on a particular interface.
show interfaces interface extensive
...
Priority Flow Control Watchdog Statistics:
Detected Recovered LastPacketDropCount TotalPacketDropCount
Queue : 0 0 0 0 0
Queue : 1 0 0 0 0
Queue : 2 0 0 0 0
Queue : 3 0 0 0 0
Queue : 4 0 0 0 0
Queue : 5 0 0 0 0
Queue : 6 0 0 0 0
Queue : 7 0 0 0 0
...You can view the actions that PFC watchdog takes in the system log.
- When the PFC watchdog is enabled on a new port, the system log displays this
message:
CDA PfcWd: PFC Watchdog detection enabled on ifd: et-0/0/16 Poll Interval:100ms Detection Period:200ms Recovery Interval:200ms - When the PFC watchdog detects a stall condition, the system log displays this
message:
CDA PfcWd: PFC Storm Detected! on ifd:et-0/0/16 Queue: 3 Priority: 3 BLOCKED for AutoRecovery Recovery Time: 200ms - When the queue recovers from the PFC pause storm, the system log displays this
message:
CDA PfcWd: PFC Storm Recovered on Port ifd:et-0/0/16 Queue: 3 Priority: 3 UNBLOCKED after AutoRecovery Recovery Time: 200ms
