22-6
ATM Switch Router Software Configuration Guide
OL-7396-01
Chapter 22
Configuring Quality of Service
About IP QoS on the Enhanced Gigabit Ethernet and Enhanced ATM Router Module Interfaces
Verifying the QoS Configuration
To verify the QoS configuration, use the following commands:
About IP QoS on the Enhanced Gigabit Ethernet and Enhanced
ATM Router Module Interfaces
DiffServ is a mechanism by which network service providers offer differing levels of network service to
different traffic classes in order to provide QoS to users.
Note
The IP QoS feature is only applicable for enhanced Gigabit Ethernet and enhanced ATM Router Modules
installed in the Catalyst 8540 MSR chassis.
In a DiffServ network, routers, within the network handle packets on different traffic flows by applying
different per-hop behaviors (PHBs). The PHB to be applied is signalled in-band, and is specified by a
DiffServ code-point (DSCP) in the IP header of each packet. No explicit out-of-band signalling protocol
such as RSVP is used. Per-hop behaviors are defined to configure granular allocation of bandwidth and
resource buffering at each node. Per-flow or per-user forwarding state is not maintained within each node
of network. The advantage of such a scheme is that many traffic flows can be aggregated to one of a small
number of PHBs, simplifying the processing requirement on each router.
The following components are the building block in the Catalyst 8540 Differentiated Services
implementation:
Packet Classification
Traffic Conditioning
•
Marking
•
Metering and Policing
Per hop behavior (PHB) definition
•
Congestion control
•
Queueing, scheduling, buffer management
Figure 22-1
shows all the DiffServ components and their distribution between the ingress and egress
points in the forwarding path.
Command
Purpose
show qos switching
Displays whether QoS-based switching is
enabled.
show qos mapping
[
source
source-interface
]
[
destination
dest-interface
]
Displays effective mapping at either the system
level or interface-pair level.
