Руководство По Проектированию для Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter
5-25
Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 5 Cisco Unified Wireless QoS
Guidelines for Deploying Wireless QoS
application to achieve its throughput requirements. This is because 802.11b cannot support the required
throughput for that throughput and frame size combination. The same amount of offered traffic, having
a frame size of 1500 bytes, does not have this issue.
throughput for that throughput and frame size combination. The same amount of offered traffic, having
a frame size of 1500 bytes, does not have this issue.
QoS Example LAN Switch Configuration
AP Switch Configuration
The QoS configuration of the AP switch is relatively trivial because the switch must trust the DSCP of
the LWAPP packets that are passed to it from the AP. There is no CoS marking on the LWAPP frames
coming from the AP. The following is an example of this configuration. Note that this configuration
addresses only the classification, and that queueing commands may be added, depending on local QoS
policy.
the LWAPP packets that are passed to it from the AP. There is no CoS marking on the LWAPP frames
coming from the AP. The following is an example of this configuration. Note that this configuration
addresses only the classification, and that queueing commands may be added, depending on local QoS
policy.
interface GigabitEthernet1/0/1
switchport access vlan 100
switchport mode access
mls qos trust dscp
spanning-tree portfast
end
In trusting the AP DSCP values, the access switch is simply trusting the policy set for that AP by the
WLC. The maximum DSCP value assigned to client traffic is based on the QoS policy applied to the
WLANs on that AP.
WLC. The maximum DSCP value assigned to client traffic is based on the QoS policy applied to the
WLANs on that AP.
WLC Switch Configuration
The QoS classification decision at the WLC-connected switch is a bit more complicated than at the
AP-connected switch, because the choice can be to either trust the DSCP or the CoS of traffic coming
from the WLC. In this decision there are a number of points to consider:
AP-connected switch, because the choice can be to either trust the DSCP or the CoS of traffic coming
from the WLC. In this decision there are a number of points to consider:
•
Traffic leaving the WLC can be either upstream (to the WLC or network) or downstream (the AP
and WLAN client). The downstream traffic is LWAPP encapsulated, and the upstream traffic is from
AP and WLAN clients, either LWAPP encapsulated or decapsulated WLAN client traffic, leaving
the WLC.
and WLAN client). The downstream traffic is LWAPP encapsulated, and the upstream traffic is from
AP and WLAN clients, either LWAPP encapsulated or decapsulated WLAN client traffic, leaving
the WLC.
•
DSCP values of LWAPP packets are controlled by the QoS policies on the WLC; the DSCP values
set on the WLAN client traffic encapsulated by the LWAPP tunnel header has not been altered from
those set by the WLAN client.
set on the WLAN client traffic encapsulated by the LWAPP tunnel header has not been altered from
those set by the WLAN client.
•
CoS values of frames leaving the WLC are set by the WLC QoS policies, regardless of whether they
are upstream, downstream, encapsulated, or decapsulated.
are upstream, downstream, encapsulated, or decapsulated.
The following example chooses to trust the CoS of settings of the WLC, because this allows a central
location for the management of WLAN QoS, rather than having to manage the WLC configuration and
an additional policy at the WLC switch connection. Other customers wishing to have a more precise
degree of control may wish to implement QoS classification policies on the WLAN-client VLANs.
location for the management of WLAN QoS, rather than having to manage the WLC configuration and
an additional policy at the WLC switch connection. Other customers wishing to have a more precise
degree of control may wish to implement QoS classification policies on the WLAN-client VLANs.
interface GigabitEthernet1/0/13
Table 5-8
Throughput Compared to Frame Size
300
600
900
1200
1500
Frame Size (bytes)
11g–54 Mbps
11.4
19.2
24.6
28.4
31.4
Throughput Mbps
11b–11 Mbps
2,2
3.6
4.7
5.4
6
Throughput Mbps