116 Chapter 4: QoS Support on the Catalyst 5000 Family of Switches
Case Study
Figure 4-4 illustrates a network that consists of two Catalyst 5000 switches implementing
several QoS features to differentiate service in network.
Figure 4-4 Case Study Topology
A time-sensitive application using the Systems Network Architecture (SNA) protocols
exists in the network depicted in Figure 4-4. In this topology, the application handles
banking transactions. The client and servers send only untagged frames. To classify frames
accordingly, the Switch-1 configuration consists of classification based on ingress port.
This configuration is illustrated by the set port qos command in Example 4-17.
Furthermore, a telephony gateway exists in the network. The telephony gateway sends
keepalive packets to other telephony devices across VLAN boundaries to the core of the
network. The telephony gateway transmits all keepalives with UDP source and destination
ports of 25000. The telephony gateway does not tag the frames, and as a result does not
apply a CoS value to transmitted frames. To classify the frames appropriately, both Catalyst
5500 switches use ACL-based classification and marking to set the CoS value of frames
matching the signature of the telephony keepalives. As a result, these switches only classify
L2
SNA Servers
SNA Clients Telephony Gateway
Catalyst 5500
with RSM
Port 3/2
Port 3/3
Switch-1
Port 3/20
Switch-2
Port 3/3
Port 3/2
Port 3/1
L3
L3
Catalyst 6500
with MSFC
Catalyst 5500
with RSFC
Port 3/1
Port 3/21
Catalyst 6500
with MSFC
L3 L3
Case Study 117
the keepalive frames and not regular traffic. Example 4-17 illustrates this ACL-based classi-
fication configuration for Switch-1.
For appropriate congestion management of frames, the switch-to-switch connections and
the ports connecting the SNA servers and the telephony gateway all utilize WRED sched-
uling. The WRED scheduling is nondefault to apply heavier weighted scheduling to packets
with a CoS value of 5. Example 4-18 shows this configuration for Switch-1.
Example 4-18 Case Study Configuration for Switch-1
Switch> (enable) show config
This command shows non-default configurations only.
Use ’show config all’ to show both default and non-default configurations.
(text deleted)
begin
!
# ***** NON-DEFAULT CONFIGURATION *****
!
(text deleted)
!
#qos
set qos enable
set qos ip-filter 5 udp any 25000 any 25000
set qos map 1q4t 1 1 cos 2
set qos map 1q4t 1 2 cos 4
set qos wred-threshold 1q4t tx queue 1 20 30 100 100
!
# default port status is enable
!
!
#module 1 : 2-port 1000BaseX Supervisor IIIG
set vlan 5 1/1-2
set trunk 1/1 off negotiate 1-1005
set trunk 1/2 off negotiate 1-1005
!
#module 3 : 24-port 10/100BaseTX Ethernet
set vlan 1 3/1
set vlan 2 3/2
set vlan 4 3/20-24
set vlan 5 3/3-19
set port qos 3/20-21 cos 5
!
(text deleted)!
#module 15 : 1-port Route Switch Feature Card
!
#module 16 empty
!
(text deleted)
!
#qos router-mac
set qos router-mac 00-30-f2-c8-8e-dc 5
set qos router-mac 00-30-f2-c8-8e-dc 4
end
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