QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet

Transcription

1 QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet The Layer 2 (L2) Overhead Specification for Shaping and Policing Parameters for Ethernet allows you to configure shaping and policing bit rates that count Layer 2 encapsulation frame lengths in addition to Layer 3 packet lengths. Feature History for QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet Release 12.0(28)S Modification This feature was introduced for the Cisco Series 4-Port Gigabit Ethernet ISE Line Card. Finding Support Information for Platforms and Cisco IOS Software Images Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear. Contents This document describes the L2 Overhead Specification feature in Cisco IOS 12.(28)S and includes the following sections: Configuring QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet, page 2 Additional References, page 3 Command Reference, page 4 Corporate Headquarters: Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA USA Copyright 2004 Cisco Systems, Inc. All rights reserved.

2 QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet Configuring QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet Configuring QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet This feature provides you with the option to configure shaping and policing QoS features that take the Layer 2 encapsulation overhead into account. Previously, outbound shaping and policing algorithms were based only on the Layer 3 packet length. This feature is enabled with the hw-module slot slot-number qos account layer2 encapsulation {arpa dot1q length} global configuration command. When enabled, the feature is enabled on all ports of the line card in both ingress and egress directions. Layer 3 accounting is the default. The no form of the command enables the default. The show policy-map interface and show interface rate commands display the additional Layer 2 overhead length. For the Cisco Series 4-Port Gigabit Ethernet ISE Line Card, the Layer 2 encapsulation overhead options to specify are as follows: Keyword Option arpa dot1q length Description Specifies Ethernet frames with a header size of 14 bytes. Specifies 802.1Q Ethernet frames with a header size of 18 bytes. Specifies a length in bytes of the Layer 2 encapsulation frame. The specified byte length in the CLI is used only in the egress (Tx) direction. Output shaping or policing must be configured on an interface. The bit rate transmitted from the line card is determined by adding the Layer 3 length of the packet to the length defined in the CLI. Incoming packets are shaped or policed based on the true Layer 2 length of the packets. For example, if the user-specified length is 14 bytes, and all packets egressing from any port are ARPA main interface packets, then the results are accurate. If some egress packets have VLAN encapsulations and some are non-vlan (main interface) packets, then the results cannot be completely accurate because the encapsulation overheads are different. On the input side, Layer 2 encapsulation overhead is 14 bytes for ARPA main interface packets and 18 bytes for 802.1Q packets, regardless of the user-specified length. Restrictions For Any Transport over ATM (AToM) the user-specified byte length on the egress of the disposition router is still added to the length of the packet, though there is no Layer 2 transport encapsulation on the packet. IPv6 does not currently support input/output Committed Access Rate (CAR). SUMMARY STEPS 1. enable 2. configure terminal 3. hw-module slot slot-number qos account layer2 encapsulation {arpa dot1q length} 4. exit 2

3 QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet Additional References DETAILED STEPS Step 1 Step 2 Command or Action enable Router> enable configure terminal Purpose Enables privileged EXEC mode. Enter your password if prompted. Enters global configuration mode. Step 3 Step 4 Router# configure terminal hw-module slot slot-number qos account layer2 encapsulation {arpa dot1q length} Router(config)# hw-module slot 1 qos account layer2 encapsulation length 14 exit Enables Layer 2 overhead accounting for calculating policed or shaped bit rates. In this example, a Layer 2 overhead of 14 bytes per frame is added to the egress traffic for interfaces on the line card in slot 1. Exits global configuration mode. Router(config)# exit Additional References The following sections provide references related to QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet. Related Documents Related Topic Quality of service (QoS) commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples Modular QoS Command-Line Interface (CLI) (MQC) Information about attaching policy maps to interfaces Traffic policing Document Title Cisco IOS Quality of Service Solutions Command Reference, Release 12.3 T Cisco IOS Quality of Service Solutions Configuration Guide Cisco IOS Quality of Service Solutions Configuration Guide Cisco IOS Quality of Service Solutions Configuration Guide 3

4 Command Reference QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet Technical Assistance Description Technical Assistance Center (TAC) home page, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content. Link Command Reference This section documents modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command reference publications. 4

5 QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet hw-module slot qos account layer2 encapsulation hw-module slot qos account layer2 encapsulation To enable Layer 2 accounting for QoS, use the command in global configuration mode. To disable, use the no form of this command. hw-module slot slot-number qos account layer2 encapsulation {arpa dot1q length} no hw-module slot slot-number qos account layer2 encapsulation {arpa dot1q length} Syntax Description slot-number arpa dot1q length Specifies the slot number of the line card to be configured for L2 overhead specification. Specifies L2 overhead frames as Ethernet frames with a header size of 14 bytes. Specifies L2 overhead frames as 802.1Q Ethernet frames with a header size of 18 bytes. Specifies length in bytes of the L2 overhead to be added for each egress frame. Defaults No Layer 2 encapsulation accounting is the default. Command Modes Global configuration Command History Release 12.0(28)S Modification This command was introduced. Usage Guidelines The no version of the command enables the default method of calculating the bit rate of traffic over an interface based on Layer 3 packet lengths. The length parameter specifies Layer 2 overhead for output traffic only. The packets transmitted from the line card are shaped or policed by adding the user-specified length to the Layer 3 length of the output packets. The incoming packets are shaped or policed according to the actual Layer 2 lengths of the encapsulations, regardless of the user-specified length. For Any Transport over ATM (AToM), the user specified byte length on the egress of the disposition router is still added to the length of the packet though there is no Layer 2 transport encapsulation on the packet. The following example specifies that 16 bytes of Layer 2 encapsulation overhead are added for each Layer 3 packet egressing from the linecard: Router(config)# hw-module slot 1 qos account layer2 encapsulation 16 5

6 hw-module slot qos account layer2 encapsulation QoS: L2 Overhead Specification for Shaping and Policing Parameters for Ethernet Related Commands Command show interfaces rate-limit show policy-map interface Description Displays information about the committed access rate (CAR) for an interface Displays the configuration of all classes configured for all service policies on the specified interface. CCVP, the Cisco logo, and Welcome to the Human Network are trademarks of Cisco Systems, Inc.; Changing the Way We Work, Live, Play, and Learn is a service mark of Cisco Systems, Inc.; and Access Registrar, Aironet, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, CCSP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Enterprise/Solver, EtherChannel, EtherFast, EtherSwitch, Fast Step, Follow Me Browsing, FormShare, GigaDrive, HomeLink, Internet Quotient, IOS, iphone, IP/TV, iq Expertise, the iq logo, iq Net Readiness Scorecard, iquick Study, LightStream, Linksys, MeetingPlace, MGX, Networkers, Networking Academy, Network Registrar, PIX, ProConnect, ScriptShare, SMARTnet, StackWise, The Fastest Way to Increase Your Internet Quotient, and TransPath are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries. All other trademarks mentioned in this document or Website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0711R) Copyright 2004 Cisco Systems, Inc. All rights reserved. 6