Cisco Systems OL-4266-08 PFC QoS Glossary

42-122

Cisco7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX

OL-4266-08

Chapter42 Con figuring PFC QoS

PFCQoS Gloss ary

PFC QoS Glossary

This section defines some of the QoS terminology used in this chapter:

•Buffers—A storage area used for handling data in transit. Buffers are used in internetworking to

compensate for differences in processing speed between network devices. Bursts of data can be stored in

buffers until they can be handled by slower processing devices. Sometimes referred to as a packet buffer.

•Class of Service (CoS) is a Layer 2 QoS label carried in three bits of either an ISL, 802.1Q, or 802.1p

header. CoS values range between zero and seven.

•Classification is the process used for selecting traffic to be marked for QoS.

•Congestion avoidance is the process by which PFC QoS reserves ingress and egress LAN port

capacity for Layer 2 frames with high-priority Layer 2 CoS values. PFCQoS implements

congestion avoidance with Layer 2 CoS value-based drop thresholds. A drop threshold is the

percentage of queue buffer utilization above which frames with a specified Layer 2 CoS value is

dropped, leaving the buffer available for frames with higher-priority Layer2 CoS values.

•Differentiated Services Code Point (DSCP) is a Layer3 QoS label carried in the six most-significant

bits of the ToS b yte in the IP header. DSCP ranges between 0 and 63.

•Frame s carry traffic at Layer 2. Layer 2 frames carry Layer 3 packets.

•IP Precedence is a Layer 3 QoS label carried in the three most-significant bits of the ToS by te in the

IP header. IP precedence ranges between zero and seven.

•Labels—See QoS labels.

144803

3 bits used for CoS

Layer 2 ISL frame

ISL header

(26 bytes)

Encapsulated frame 1...

(24.5 KB)

FCS

(4 bytes)

Layer 2 802.1Q and 802.1p frame

Preamble Start frame

delimiter DA SA Tag PT Data FCS

3 bits used for CoS (user priority)

144804

Len

Layer 3 IPv4 packet

Version

length

ToS

(1 byte) ID Offset TTL Proto FCS IP-SA IP-DA Data

3 bits for IP precedence

144804

Len

Layer 3 IPv4 packet

Version

length

ToS

(1 byte) ID Offset TTL Proto FCS IP-SA IP-DA Data

3 bits for IP precedence

Contents

Main CHAPT ER Configuring PFC QoS Understanding How PFC QoS Works Port Types Supported by PFC QoS Overview Page Page Page Figure 42-4 PFC QoS Features and Component Overview Component Overview Ingress LAN Port PFC QoS Features These sections provide an overview of the ingress port QoS features: Flowchart of Ingress LAN Port PFC QoS Features Figure 42-5 shows how traffic flows through the ingress LAN port PFC QoS features. Port Trust Ingress Congestion Avoidance PFC and DFC QoS Features Supported Policy Feature Cards Supported Distributed Forwarding Cards PFC and DFC QoS Feature List and Flowchart Cisco7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX OL-4266-08 Chapter42 Con figuring PFC QoS Understanding How PFCQoS Works Figure 42-6 shows how traffic flows through the QoS features on the PFC and DFCs. Figure 42-6 QoS Features on the PFC and DFCs Ingress PFC QoS Egress PFC QoS Internal DSCP Values Port-Based PFC QoS and VLAN-Based PFCQoS PFC QoS Egress Port Features Flowchart of PFC QoS Egress LAN Port Features Egress CoS Values Egress DSCP Mutation with a PFC3 Egress ToS Byte Egress PFC QoS Interfaces Egress ACL Support for Remarked DSCP Marking on Egress OSM Ports Understanding Classification and Marking Classification and Marking at Trusted and Untrusted Ingress Ports Classification and Marking at Untrusted Ingress Ports Ingress Classification and Marking at Trusted Ports Classification and Marking at Ingress OSM Ports Classification and Marking on the PFC Using Service Policies and Policy Maps Classification and Marking on the MSFC Policers Overview of Policers Aggregate Policers Microflow Policers Understanding Port-Based Queue Types Ingress and Egress Buffers and Layer 2 CoS-Based Queues Page Ingress Queue Types C C S a Egress Queue Types Module to Queue Type Mappings Page PFC QoS Default Configuration PFC QoS Global Settings Default Values With PFC QoS Enabled Receive-Queue Limits Transmit-Queue Limit s Bandwidth Allocation Ratios Default Drop-Threshold Percentages and CoS Value Mappings 1q2t Receive Queues 1q4t Receive Queues 1p1q4t Receive Queues 1p1q0t Receive Queues 1p1q8t Receive Queues 1q8t Receive Queues 2q8t Receive Queues 8q4t Receive Queues Page Page Page 8q8t Receive Queues 2q2t Transmit Queues 1p2q2t Transmit Queues 1p3q8t Transmit Queues 1p7q4t Transmit Queues Page Page 1p7q8t Transmit Queues 1p3q1t Transmit Queues 1p2q1t Transmit Queues Default Values With PFC QoS Disabled PFC QoS Configuration Guidelines and Restrictions General Guidelines PFC3 Guidelines PFC2 Guidelines Class Map Command Restrictions Policy Map Command Restrictions Policy Map Class Command Restrictions Supported Granularity for CIR and PIR Rate Values Supported Granularity for CIR and PIR Token Bucket Sizes IP Precedence and DSCP Values Configuring PFC QoS Enabling PFC QoS Globally Enabling Ignore Port Trust Configuring DSCP Transparency Enabling Queueing-Only Mode Enabling Microflow Policing of Bridged Traffic Enabling VLAN-Based PFC QoS on Layer 2 LAN Ports Enabling Egress ACL Support for Remarked DSCP Creating Named Aggregate Policers Page Page Configuring a PFC QoS Policy PFC QoS Policy Configuration Overview Configuring MAC ACLs Configuring Protocol-Independent MAC ACL Filtering Enabling VLAN-Based MAC QoS Filtering Configuring MAC ACLs Configuring ARP ACLs for QoS Filtering Configuring a Class Map Creating a Class Map Class Map Filtering Guidelines and Restrictions Configuring Filtering in a Class Map Verifying Class Map Configuration Configuring a Policy Map Creating a Policy Map Policy Map Class Configuration Guidelines and Restrictions Creating a Policy Map Class and Configuring Filtering Configuring Policy Map Class Actions Page Page Page Page Verifying Policy Map Configuration Attaching a Policy Map to an Interface Page Configuring Egress DSCP Mutation on a PFC3 Configuring Named DSCP Mutation Maps Attaching an Egress DSCP Mutation Map to an Interface Configuring Ingress CoS Mutation on IEEE 802.1Q Tunnel Ports Ingress CoS Mutation Configuration Guidelines and Restrictions Configuring Ingress CoS Mutation Maps Applying Ingress CoS Mutation Maps to IEEE 802.1Q Tunnel Ports Configuring DSCP Value Maps Mapping Received CoS Values to Internal DSCP Values Mapping Received IP Precedence Values to Internal DSCP Values Configuring DSCP Markdown Values Page Mapping Internal DSCP Values to Egress CoS Values Configuring the Trust State of Ethernet LAN and OSM Ports Configuring the Ingress LAN Port CoS Value Configuring Standard-Queue Drop Threshold Percentages Configuring a Tail-Drop Receive Queue Configuring a WRED-Drop Transmit Queue Configuring a WRED-Drop and Tail-Drop Receive Queue Configuring a WRED-Drop and Tail-Drop Transmit Queue Configuring 1q4t/2q2t Tail-Drop Threshold Percentages Page Mapping QoS Labels to Queues and Drop Thresholds Queue and Drop Threshold Mapping Guidelines and Restrictions Configuring DSCP-Based Queue Mapping Enabling DSCP-Based Queue Mapping Configuring Ingress DSCP-Based Queue Mapping Page Note The receive queue mapping is shown in the second queue thresh dscp-map displayed by the show queueing interface command. This example shows how to verify the configuration: Mapping DSCP Values to Standard Transmit-Queue Thresholds Mapping DSCP Values to the Transmit Strict-Priority Queue Mapping CoS Values to Standard Receive-Queue Thresholds Mapping CoS Values to Standard Transmit-Queue Thresholds Mapping CoS Values to Strict-Priority Queues Mapping CoS Values to Tail-Drop Thresholds on 1q4t/2q2t LAN Ports Allocating Bandwidth Between Standard Transmit Queues Page Setting the Receive-Queue Size Ratio Configuring the Transmit-Queue Size Ratio Common QoS Scenarios Sample Network Design Overview Classifying Traffic from PCs and IP Phones in the Access Layer Page Page Accepting the Traffic Priority Value on Interswitch Links Prioritizing Traffic on Interswitch Links Page Page Using Policers to Limit the Amount of Traffic from a PC Page PFC QoS Glossary