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A Quick MQC ReviewOver time, various Cisco IOS Software versions and hardware platforms have invented different ways to control QoS behaviors (policing, marking, queuing, and dropping). There have been many different CLIs that accomplish very similar things. A GSR QoS configuration was different from a 7200 configuration was different from a 7500 configuration, and so forth. Along came MQC. MQC's goal is to unify all the QoS configuration steps into a single, flexible CLI that can be used across all IOS platforms. This chapter covers only the MQC, because that is the preferred way to configure QoS. You can configure QoS services in other ways, but they are not covered here. If you have questions about a specific router model or software version, see the relevant documentation. MQC is very powerful, and it can be a bit complex to the beginner. This section is a quick review of MQC. This is not a book on QoS, so this chapter doesn't go into great detail on the different types of services—merely how you can configure them with MQC. MQC has three pieces:
The options you have within each of these pieces vary between code versions and platforms, so some of the options shown here might not be available to you. The basic idea remains constant, though. Configuring a Class MapThe first step in using MQC is to build a class map. Not surprisingly, you do this with the class-map command:
vxr12(config)#class-map ?
WORD class-map name
match-all Logical-AND all matching statements under this classmap
match-any Logical-OR all matching statements under this classmapm
The match-all and match-any keywords let you specify whether traffic matches this class, if it matches all the rules in this class or any of them, respectively. The default is match-all. You create a class by giving it a name. This puts you in a submode called config-cmap: vxr12(config)#class-map voice vxr12(config-cmap)#? QoS class-map configuration commands: description Class-Map description exit Exit from QoS class-map configuration mode match classification criteria no Negate or set default values of a command rename Rename this class-mapm The most useful option under config-cmap is match, which lets you define the traffic you want to match with this class map. Its options are as follows:
vxr12(config-cmap)#match ?
access-group Access group
any Any packets
class-map Class map
cos IEEE 802.1Q/ISL class of service/user priority values
destination-address Destination address
fr-de Match on Frame-relay DE bit
input-interface Select an input interface to match
ip IP specific values
mpls Multi Protocol Label Switching specific values
not Negate this match result
protocol Protocol
qos-group Qos-group
source-address Source addressm
There are a few interesting options here. Note that you can match a class map; this lets you define hierarchical classes. A class called "Business," for example, can match an "Email" class and a "Payroll" class you define so that all business-class e-mail and all traffic to or from the payroll department gets the same treatment. You can also match not, which lets you match everything except a specific thing. You might now start to understand the awesome power of MQC. Table 6-1 lists the matches of interest here.
For the example in this chapter, create a simple LLQ policy matching MPLS EXP 5 traffic, and assume it is Voice over IP (VoIP) traffic. The necessary configuration is as follows: class-map match-all voice match mpls experimental 5 policy-map llq class voice priority percent 30 This defines a class that matches any MPLS traffic that has the EXP bits set to 5 and then defines a policy for that traffic that gives the traffic 30 percent of a link's bandwidth. The policy map hasn't been enabled on an interface yet; you'll see that in a minute. You can match multiple values with the same line using the following command sequence: class-map match-any bronze-service match mpls experimental 0 1 This matches any packets that have an MPLS EXP of 0 or 1. As with route maps, multiple values specified within the same match clause (such as match mpls experimental 0 1) are implicitly ORed together; a packet can't have both EXP 0 and EXP 1, so this implicit ORing makes sense. You can also match more than one criteria within a class, and you can use the match-any and match-all statements to decide how you want to match traffic. For example, the following policy matches traffic that has MPLS EXP 5 or traffic that entered the router on interface POS3/0: class-map match-any gold match mpls experimental 5 match input-interface POS3/0 The following policy matches any traffic that has MPLS EXP 5 and that came in on interface POS3/0: class-map match-all gold match mpls experimental 5 match input-interface POS3/0 See the difference? The first class map is match-any (the default), and the second is match-all. The output for show class-map {class-map-name} shows you the configured class maps, as demonstrated in Example 6-1. Example 6-1 Displaying the Configured Class Maps
vxr12#show class-map
Class Map match-all gold (id 2)
Match mpls experimental 5
Match input-interface POS3/0
Class Map match-any class-default (id 0)
Match any
Class Map match-all voice (id 3)
Match mpls experimental 5
Note the class-default class in this list. class-default is a predefined class; it can be used to match any traffic that doesn't match any other class. You'll read more about this in the next section. Configuring a Policy MapAfter you define the class maps you want to match, you need to associate the class of traffic with a behavior. You create the behavior with the policy-map command, which, like class-map, puts you in a special submode: vxr12(config)#policy-map ? WORD policy-map name vxr12(config)#policy-map llq vxr12(config-pmap)#? QoS policy-map configuration commands: class policy criteria description Policy-Map description exit Exit from QoS policy-map configuration mode no Negate or set default values of a command rename Rename this policy-map Under the config-pmap submode, you specify the class you want to match. This puts you in the config-pmap-c submode: vxr12(config)#policy-map llq vxr12(config-pmap)#class voice vxr12(config-pmap-c)#? QoS policy-map class configuration commands: bandwidth Bandwidth exit Exit from QoS class action configuration mode no Negate or set default values of a command police Police priority Strict Scheduling Priority for this Class queue-limit Queue Max Threshold for Tail Drop random-detect Enable Random Early Detection as drop policy service-policy Configure QoS Service Policy set Set QoS values shape Traffic Shaping You can do all sorts of things here. Table 6-2 shows the options of interest for the purposes of this chapter.
The syntax for all those commands makes them look intimidating, but it's easy. Example 6-2 shows the LLQ policy you read about earlier, using the voice class map that's already been defined. Example 6-2 LLQ Policy with a Defined voice Class Mapclass-map match-any voice match mpls experimental 5 policy-map llq class voice priority percent 30 A predefined class called class-default implicitly matches anything not matched by a specific class; this gives you an easy way to give all unmatched packets the same treatment if you want to. For example, you can expand this class map to cover two types of service: voice and business. Business class is any data that has an MPLS EXP of 3 or 4, that is allocated 60 percent of the link bandwidth, and in which MPLS-based VoIP packets (EXP 5) get 30 percent of the link bandwidth. All other traffic is matched with class-default, which gets the remaining 10 percent of link bandwidth. This requires both a new class (to match the EXP 3 and 4 traffic) and a new policy map to define the treatment these classes get (see Example 6-3). Example 6-3 Defining a Policy Map with a Business Classclass-map match-all business match mpls experimental 3 4 class-map match-all voice match mpls experimental 5 policy-map business-and-voice class voice priority percent 30 class business bandwidth percent 60 class class-default bandwidth percent 10 The show policy-map command gives you a fair amount of detail about the policy maps defined on a router and the class maps inside them. Example 6-4 shows two policy maps—llq and business-and-voice; the llq policy matches the voice class, and the business-and-voice policy matches the voice and business classes. Example 6-4 Displaying Policy Map Information
vxr12#show policy-map
Policy Map business-and-voice
Class voice
Weighted Fair Queuing
Strict Priority
Bandwidth 30 (%)
Class business
Weighted Fair Queuing
Bandwidth 60 (%) Max Threshold 64 (packets)
Class class-default
Weighted Fair Queuing
Bandwidth 10 (%) Max Threshold 64 (packets)
Policy Map llq
Class voice
Weighted Fair Queuing
Strict Priority
Bandwidth 30 (%)
Configuring a Service PolicyThis is the easiest part of the MQC. So far, you've seen a few class definitions and a policy definition. Now all that's left is to apply the policy to an interface, as shown in Example 6-5. Example 6-5 Applying a Service Policy to a Router Interfacevxr12(config-if)#service-policy ? history Keep history of QoS metrics input Assign policy-map to the input of an interface output Assign policy-map to the output of an interface vxr12(config-if)#service-policy out vxr12(config-if)#service-policy output ? WORD policy-map name vxr12(config-if)#service-policy output llq That's it. Note that you can have both an inbound and an outbound service policy. show policy-map interface interface gives you details about which policy maps are applied to an interface, as demonstrated in Example 6-6. Example 6-6 Determining Which Policy Maps Are Applied to an Interface
vxr12#show policy-map interface pos3/0
POS3/0
Service-policy output: llq
Class-map: voice (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: mpls experimental 5
Weighted Fair Queuing
Strict Priority
Output Queue: Conversation 264
Bandwidth 30 (%)
Bandwidth 46500 (kbps) Burst 1162500 (Bytes)
(pkts matched/bytes matched) 0/0
(total drops/bytes drops) 0/0
Class-map: class-default (match-any)
21 packets, 15744 bytes
5 minute offered rate 3000 bps, drop rate 0 bps
Match: any
If you're still not comfortable with either MQC or the underlying QoS concepts such as CBWFQ and LLQ, it is highly recommended that you check out the references in Appendix B. |
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