Modular QoS Overview on Cisco ASR 9000 Series Routers
Information About Modular Quality of Service on Cisco ASR 9000 Series Routers
QC-2
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide
OL-23108-02
• Additional Cisco IOS XR QoS Supported Features, page QC-5
Benefits of Cisco ASR 9000 Series Routers QoS Features
The Cisco IOS XR QoS features enable networks to control and predictably service a variety of
networked applications and traffic types. Implementing Cisco
IOS XR QoS in your network promotes
the following benefits:
• Control over resources. You have control over which resources (bandwidth, equipment, wide-area
facilities, and so on) are being used. For example, you can limit bandwidth consumed over a
backbone link by FTP transfers or give priority to an important database access.
• Tailored services. If you are an Internet Service Provider (ISP), the control and visibility provided
by QoS enables you to offer carefully tailored grades of service differentiation to your customers.
• Coexistence of mission-critical applications. Cisco IOS XR QoS features make certain of the
following conditions:
–
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.
–
That other applications using the link get their fair service without interfering with
mission-critical traffic.
QoS Techniques on Cisco ASR 9000 Series Routers
QoS on Cisco IOS XR software relies on the following 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.
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