Руководство По Проектированию для Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter
5-3
Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 5 Cisco Unified Wireless QoS
Wireless QoS Deployment Schemes
Upstream and Downstream QoS
illustrates the definition of radio upstream and radio downstream QoS.
Figure 5-2
Upstream and Downstream QoS
shows the following:
•
Radio downstream QoS—Traffic leaving the AP and traveling to the WLAN clients. Radio
downstream QoS is the primary focus of this chapter, because this is still the most common
deployment. The radio client upstream QoS depends on the client implementation.
downstream QoS is the primary focus of this chapter, because this is still the most common
deployment. The radio client upstream QoS depends on the client implementation.
•
Radio upstream QoS—Traffic leaving the WLAN clients and traveling to the AP. WMM provides
upstream QoS for WLAN clients supporting WMM.
upstream QoS for WLAN clients supporting WMM.
Table 5-1
QoS Parameters
Transmission
Quality
Description
Latency
Latency (or delay) is the amount of time it takes for a packet to reach the receiving
endpoint after being transmitted from the sending endpoint. This time period is called
the end-to-end delay and can be divided into two areas:
endpoint after being transmitted from the sending endpoint. This time period is called
the end-to-end delay and can be divided into two areas:
•
Fixed network delay—Includes encoding and decoding time (for voice and
video), and the finite amount of time required for the electrical or optical pulses
to traverse the media en route to their destination.
video), and the finite amount of time required for the electrical or optical pulses
to traverse the media en route to their destination.
•
Variable network delay—Generally refers to network conditions, such as queuing
and congestion, that can affect the overall time required for transit.
and congestion, that can affect the overall time required for transit.
Jitter
Jitter (or delay-variance) is the difference in the end-to-end latency between packets.
For example, if one packet requires 100 ms to traverse the network from the source
endpoint to the destination endpoint, and the next packet requires 125 ms to make the
same trip, the jitter is calculated as 25 ms.
For example, if one packet requires 100 ms to traverse the network from the source
endpoint to the destination endpoint, and the next packet requires 125 ms to make the
same trip, the jitter is calculated as 25 ms.
Loss
Loss (or packet loss) is a comparative measure of packets successfully transmitted
and received to the total number that were transmitted. Loss is expressed as the
percentage of packets that were dropped.
and received to the total number that were transmitted. Loss is expressed as the
percentage of packets that were dropped.
153866
Si
LWAPP
Network Upstream
Network Downstream
Radio Downstream
Radio Upstream
LWAPP