- 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
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- 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
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- play_arrow Configuration Statements and Operational Commands
Configuring Class of Service for MPLS LSPs
The following sections provide an overview of MPLS class of service (CoS) and describe how to configure the MPLS CoS value:
Class of Service for MPLS Overview
When IP traffic enters an LSP tunnel, the ingress router marks all packets with a CoS value, which is used to place the traffic into a transmission priority queue. On the router, for SDH/SONET and T3 interfaces, each interface has four transmit queues. The CoS value is encoded as part of the MPLS header and remains in the packets until the MPLS header is removed when the packets exit from the egress router. The routers within the LSP utilize the CoS value set at the ingress router. The CoS value is encoded by means of the CoS bits (also known as the EXP or experimental bits). For more information, see MPLS Label Allocation.
MPLS class of service works in conjunction with the router’s general CoS functionality. If you do not configure any CoS features, the default general CoS settings are used. For MPLS class of service, you might want to prioritize how the transmit queues are serviced by configuring weighted round-robin, and to configure congestion avoidance using random early detection (RED)..
Configuring the MPLS CoS Values
When traffic enters an LSP tunnel, the CoS value in the MPLS header is set in one of three ways:
The number of the output queue into which the packet was buffered and the packet loss priority (PLP) bit are written into the MPLS header and are used as the packet’s CoS value. This behavior is the default, and no configuration is required. Default MPLS EXP Classifier explains the default MPLS CoS values, and summarizes how the CoS values are treated.
You set a fixed CoS value on all packets entering the LSP tunnel. A fixed CoS value means that all packets entering the LSP receive the same class of service.
You set an MPLS EXP rewrite rule to override the default behavior.
To set a fixed CoS value on all packets entering the LSP, include
the class-of-service statement:
class-of-service cos-value;
You can include this statement at the following hierarchy levels:
[edit protocols mpls][edit protocols mpls label-switched-path path-name][edit protocols mpls label-switched-path path-name primary path-name][edit protocols mpls label-switched-path path-name secondary path-name][edit protocols rsvp interface interface-name link-protection][edit protocols rsvp interface interface-name link-protection bypass destination][edit logical-systems logical-system-name protocols mpls][edit logical-systems logical-system-name protocols mpls label-switched-path path-name][edit logical-systems logical-system-name protocols mpls label-switched-path path-name primary path-name][edit logical-systems logical-system-name protocols mpls label-switched-path path-name secondary path-name][edit logical-systems logical-system-name protocols rsvp interface interface-name link-protection ][edit logical-systems logical-system-name protocols rsvp interface interface-name link-protection bypass destination]
The CoS value set using the class-of-service statement
at the [edit protocols mpls] hierarchy level supersedes
the CoS value set at the [edit class-of-service] hierarchy
level for an interface. Effectively, the CoS value configured for
an LSP overrides the CoS value set for an interface.
The class-of-service statement at the [edit
protocols mpls label-switched-path] hierarchy level assigns
an initial EXP value for the MPLS shim header of packets in the LSP.
This value is initialized at the ingress routing device only and overrides
the rewrite configuration established for that forwarding class. However,
the CoS processing (weighted round robin [WRR] and RED) of packets
entering the ingress routing device is not changed by the class-of-service statement on an MPLS LSP. Classification is still based on the behavior
aggregate (BA) classifier at the [edit class-of-service] hierarchy level or the multifield classifier at the [edit firewall] hierarchy level.
We recommend configuring all routing devices along the LSP to have the same input classifier for EXP, and, if a rewrite rule is configured, all routing devices should have the same rewrite configuration. Otherwise, traffic at the next LSR might be classified into a different forwarding class, resulting in a different EXP value being written to the EXP header.
The CoS value can be a decimal number from 0 through 7. This number corresponds to a 3-bit binary number. The high-order 2 bits of the CoS value select which transmit queue to use on the outbound interface card.
The low-order bit of the CoS value is treated as the PLP bit and is used to select the RED drop profile to use on the output queue. If the low-order bit is 0, the non-PLP drop profile is used, and if the low-order bit is 1, the PLP drop profile is used. It is generally expected that RED will more aggressively drop packets that have the PLP bit set. For more information about RED and drop profiles, see RED Drop Profiles for Congestion Management.
Configuring the PLP drop profile to drop packets more aggressively (for example, setting the CoS value from 6 to 7) decreases the likelihood of traffic getting through.
Table 1 summarizes how MPLS CoS values correspond to the transmit queue and PLP bit. Note that in MPLS, the mapping between the CoS bit value and the output queue is hard-coded. You cannot configure the mapping for MPLS; you can configure it only for IPv4 traffic flows, as described in Understanding How Forwarding Classes Assign Classes to Output Queues.
MPLS CoS Value | Bits | Transmit Queue | PLP Bit |
|---|---|---|---|
0 | 000 | 0 | Not set |
1 | 001 | 0 | Set |
2 | 010 | 1 | Not set |
3 | 011 | 1 | Set |
4 | 100 | 2 | Not set |
5 | 101 | 2 | Set |
6 | 110 | 3 | Not set |
7 | 111 | 3 | Set |
Because the CoS value is part of the MPLS header, the value is associated with the packets only as they travel through the LSP tunnel. The value is not copied back to the IP header when the packets exit from the LSP tunnel.
To configure class of service (CoS) for Multiprotocol Label Switching (MPLS) packets in a label-switched path (LSP):
Specify the CoS value
If you do not specify a CoS value, the IP precedence bits from the packet’s IP header are used as the packet’s CoS value.
Rewriting IEEE 802.1p Packet Headers with the MPLS CoS Value
For Ethernet interfaces installed on a T Series router or an M320 router with a peer connection to an M Series router or a T Series router, you can rewrite both MPLS CoS and IEEE 802.1p values to a configured value (the MPLS CoS values are also known as the EXP or experimental bits). Rewriting these values allows you to pass the configured value to the Layer 2 VLAN path. To rewrite both the MPLS CoS and IEEE 802.1p values, you must include the EXP and IEEE 802.1p rewrite rules in the class of service interface configuration. The EXP rewrite table is applied when you configure the IEEE 802.1p and EXP rewrite rules.
For information about how to configure the EXP and IEEE 802.1p rewrite rules, see Rewriting Packet Headers to Ensure Forwarding Behavior.
