508 CHAPTER 18: QUALITY OF SERVICE (QO S) AND R ESOURCE R ESERVATION PROTOCOL (RSVP)Layer 2SwitchingModules3 MultilayerSwitchingModulesqos classifier define Defines a flow or nonflow classifier on a Multilayer Switching Module.Valid Minimum Abbreviationq cl defImportant Considerationsn Classifiers define how the module groups packets so that it canschedule them with the appropriate service level. QoS supports flowand nonflow classifiers:n Flow classifiers apply to routed IP multicast and IP unicast packets.You can define up to 100 flow classifiers. Each filter (address andport pattern) in a flow classifier counts toward the limit.n Nonflow classifiers apply to bridged or routed traffic that isassociated with a specific protocol (IP, TCP/IP, IPX, and AppleTalk) orto a custom protocol (Ethertype or Destination Service AccessPoint/Source Service Access Point (DSAP/SSAP). You can also usethem to apply IEEE 802.1p tag values to forwarded frames. Youcan define up to 16 nonflow classifiers. All 16 nonflow classifiersare in use by default.n The default classifier number is 499. You cannot remove or modifythis default classifier. However, you can remove any of the predefinedclassifiers (for example, if you need another nonflow classifier). See“qos classifier remove” later in this chapter for more information.n When you define a filter (address and port pattern) for a flowclassifier, select a source and destination start and end port rangesthat are as small as possible (for example, a single port). If the classifierapplies to a wide range of Transmission Control Protocol (TCP) or UserDatagram Protocol (UDP) ports, you increase the amount of classifiedtraffic on the module and consume valuable QoS resources.n A classifier can have only one control applied to it.n If you select custom when you define a nonflow classifier, you areprompted to select the protocol by Ethertype or DSAP/SSAP. After youselect a protocol, you are prompted to provide the hexidecimal ranges.Depending on the number of VLANs defined, you can define a maximumof 3 custom protocols that can have controls applied to them. Thislimitation does not apply to non-controlled custom protocols.
