QoS-MQC Support for MTR
QoS-MQC Support for MTR
Last Updated: July 23, 2010
The QoS-MQC Support for MTR feature enables Multitopology Routing (MTR) traffic classification. Traffic classification is used to associate different classes of traffic with different topologies when multiple topologies are configured on the same device. This module describes how to configure quality of service (QoS) with modular QoS CLI (MQC) support for MTR.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
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Prerequisites for QoS-MQC Support for MTR
Restrictions for QoS-MQC Support for MTR
Information About QoS-MQC Support for MTR
MTR Traffic Classification
MTR cannot be enabled on a router until traffic classification is configured, even if only one class-specific topology is configured. Traffic classification is used to configure topology specific forwarding behaviors when multiple topologies are configured on the same router. Traffic classification must be applied consistently throughout the network. Class-specific packets are associated with the corresponding topology table forwarding entries.
Traffic classification is configured by using the Modular QoS CLI (MQC). MTR traffic classification is similar to QoS traffic classification. However, there is an important distinction. MTR traffic classification is defined globally for each topology, rather than at the interface level as in QoS.
A subset of DSCP bits is used to encode classification values in the IP packet header. You configure a class map to define the traffic class by entering the class-map command in global configuration mode. Only the match-any keyword is supported for MTR. You associate the traffic class with a policy by configuring the policy-map type class-routing ipv4 unicast command in global configuration mode. You activate the policy for the topology by configuring the service-policy type class-routing command in global address family configuration mode. When configured, the service policy is associated with all interfaces on the router.
Some of the same goals can be achieved through QoS configuration, to which MTR provides a more powerful and flexible alternative.You can configure MTR traffic classification and IP Differentiated Services or IP Precedence-based traffic classification in the same network. However, MTR requires exclusive use of some subset of the DSCP bits in the IP packet header for specific topology traffic. In a network where MTR and QoS traffic classification are configured, simultaneous configuration must be carefully coordinated.
For detailed steps, see the Configuring MTR Traffic Classification section.
How to Configure QoS-MQC Support for MTR
Configuring MTR Traffic Classification
Before You BeginSUMMARY STEPS
Configuration Examples for QoS-MQC Support for MTR
Examples MTR Traffic Classification
The following example shows how to configure classification and activate MTR for two topologies:
global-address-family ipv4 topology VOICE all-interfaces exit topology VIDEO forward-base maximum routes 1000 90 exit exit class-map match-any VOICE-CLASS match ip dscp 9 exit class-map match-any VIDEO-CLASS match ip dscp af11 exit policy-map type class-routing ipv4 unicast MTR class VOICE-CLASS select-topology VOICE exit class VIDEO-CLASS select-topology VIDEO exit exit global-address-family ipv4 service-policy type class-routing MTR end
The following example shows how to display detailed information about the VOICE and VIDEO topologies:
Router# show topology detail Topology: base Address-family: ipv4 Associated VPN VRF is default Topology state is UP Associated interfaces: Ethernet0/0, operation state: UP Ethernet0/1, operation state: DOWN Ethernet0/2, operation state: DOWN Ethernet0/3, operation state: DOWN Loopback0, operation state: UP Topology: VIDEO Address-family: ipv4 Associated VPN VRF is default Topology state is UP Topology fallback is enabled Topology maximum route limit 1000, warning limit 90% (900) Associated interfaces: Topology: VOICE Address-family: ipv4 Associated VPN VRF is default Topology state is UP Topology is enabled on all interfaces Associated interfaces: Ethernet0/0, operation state: UP Ethernet0/1, operation state: DOWN Ethernet0/2, operation state: DOWN Ethernet0/3, operation state: DOWN Loopback0, operation state: UP Topology: base Address-family: ipv4 multicast Associated VPN VRF is default Topology state is DOWN Multicast multi-topology mode is enabled. Route Replication Enabled: from unicast topology VOICE all route-map BLUE Associated interfaces: Ethernet0/0, operation state: UP Ethernet0/1, operation state: DOWN Ethernet0/2, operation state: DOWN Ethernet0/3, operation state: DOWN Loopback0, operation state: UP
The following example shows how to display the classification values for the VOICE and VIDEO topologies:
Router# show mtm table MTM Table for VRF: default, ID:0 Topology Address Family Associated VRF Topo-ID base ipv4 default 0 VOICE ipv4 default 2051 Classifier: ClassID:3 DSCP: cs1 DSCP: 9 VIDEO ipv4 default 2054 Classifier: ClassID:4 DSCP: af11
Feature Information for QoS-MQC Support for MTR
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
base topology--The entire network for which the usual set of routes are calculated. This topology is the same as the default global routing table that exists without Multitopology Routing (MTR) being used.
class-specific topology--New topologies that are defined over and above the existing base topology; each class-specific topology is represented by its own Routing Information Base (RIB) and Forwarding Information Base (FIB).
classification--Selection and matching of traffic that needs to be provided with a different treatment based on its mark. Classification is a read-only operation.
DSCP--differentiated services code point. Six bits in the Type of Service (ToS) field. Two bits are used for Explicit Congestion Notification, which are used to mark the packet.
incremental forwarding mode--Incremental forwarding mode is designed to support transitional or incremental deployment of MTR, where devices are in the network that are not MTR enabled. In this mode, the device looks for a forwarding entry first in the class-specific FIB. If an entry is not found, the device then looks for the longest match in the base topology FIB. If an entry is found in the base topology FIB, the packet is forwarded on the base topology. If a forwarding entry is not found in the base topology FIB, the packet is dropped.
marking--Setting a value in the packet or frame. Marking is a read and write operation.
multitopology--Multitopology means that each topology routes and forward a subset of the traffic as defined by the classification criteria.
NLRI--Network Layer Reachability Information.
strict forwarding mode--Strict forwarding mode is the default forwarding mode for MTR. Only routes in the topology-specific routing table are considered. Among these, the longest match for the destination address is used. If no route containing the destination address can be found in the topology specific table, the packet is dropped.
TID--Topology Identifier. Each topology is configured with a unique topology ID. The topology ID is configured under the routing protocol and is used to identify and group NLRI for each topology in updates for a given protocol.
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