Qos Techniques; Packet Classification And Marking - Cisco ASR 9000 Series Configuration Manual

QoS Techniques

• Tailored services. If you are an Internet Service Provider (ISP), the control and visibility provided by
• Coexistence of mission-critical applications. Cisco IOS XR QoS features ensure:
QoS Techniques
QoS on Cisco IOS XR software relies on these techniques to provide for end-to-end QoS delivery across a
heterogeneous network:

• Packet classification and marking

• Congestion management
• Congestion avoidance
Before implementing the QoS features for these techniques, you should identify and evaluate the traffic
characteristics of your network because not all techniques are appropriate for your network environment.
Packet Classification and Marking
Packet classification and marking techniques identify the traffic flow, and provide the capability to partition
network traffic into multiple priority levels or classes of service. After classification is complete, any other
QoS actions can be performed.
Identification of a traffic flow can be performed by using several methods within a single router, such as
access control lists (ACLs), protocol match, IP precedence, IP differentiated service code point (DSCP), MPLS
EXP bit, or Class of Service (CoS).
Marking of a traffic flow is performed by:
• Setting IP Precedence or DSCP bits in the IP Type of Service (ToS) byte.
• Setting CoS bits in the Layer 2 headers.
• Setting EXP bits within the imposed or the topmost Multiprotocol Label Switching (MPLS) label.
• Setting qos-group and discard-class bits.
Marking can be carried out:
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
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QoS enables you to offer carefully tailored grades of service differentiation to your customers.
◦ That bandwidth and minimum delays required by time-sensitive multimedia and voice applications
are available.
◦ That your WAN is used efficiently by mission-critical applications that are most important to your
business.
◦ That bandwidth and minimum delays required by time-sensitive multimedia and voice applications
are available.
◦ Cisco ASR 9000 series router supports 10,000 unique policy-maps per system and 2,000 unique
policy-maps per Linecard (regardless of Linecard Type).
◦ That other applications using the link get their fair service without interfering with mission-critical
traffic.
Modular QoS Overview