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Chapter 11: Deployment Examples CLI
Voice traffic is very sensitive to delay and cannot tolerate packet loss without loss of voice quality. When other traffic is competing
with voice traffic for bandwidth, it becomes essential to prevent that traffic from interfering with voice traffic. Because voice traffic
for a single call requires very little bandwidth—typically from 8 to 64 kbps depending on the voice codec useda good approach
for setting its rate is to calculate the bandwidth necessary for a voice call plus related telephony traffic from a single user’s
computer, softphone, or handset and then multiply that by the potential number of concurrent VoIP users.
Class 5: streaming media using the Microsoft Media Server (MMS) protocol on TCP Port 1755
Although streaming media is also time sensitive, streaming media software for both clients and servers offers limited buffering to
prevent choppy sounds and pixelated video when network congestion occurs. Because congestion for more than a few seconds
can adversely effect streaming media, it is important to assign this type of traffic a higher priority than other types, but its priority
should be lower than that for voice, which is even more sensitive to delay.
Class 3: data traffic for e-mail using the following protocols:
SMTP (Simple Mail Transfer Protocol) on TCP Port 25
POP3 (Post Office Protocol version 3) on TCP Port 110
Then you create classifier profiles that reference these traffic-to-class mappings. You bind the profiles to the wifi0.1 and eth0
interfaces so that cluster members map the traffic matching these profiles that arrives at these interfaces to the proper SmartPath
classes.
You next define a QoS policy that defines how the cluster members prioritize and process the traffic mapped to Classes 6, 5, and
3. The QoS policy (named voice”) is shown in Figure 11-9 and has these settings:
Class 6 (voice)
Forwarding: strict (Cluster members forward traffic mapped to this class immediately without queuing it.)
Maximum rate for all Class 6 traffic: 512 kbps, which supports an 8- to 64-kbps VoIP call (depending on the compression that the
codec provides) plus other telephony traffic such as DHCP, DNS, HTTP, and TFTP.
Class 5 (streaming media)
Forwarding: WRR (weighted round robin) with a weight of 90
By assigning class 5 a higher weight (90) than Class 3 and 2 weights (Class 3 = 60, Class 2 = 30), you give streaming media
roughly a 3:2 priority over Class 3 traffic and a 3:1 priority over Class 2 traffic.
Maximum traffic rate for all Class 5 traffic: 20,000 kbps
You change the bandwidth available for streaming media when there is no competition for it (the default rate for Class 5 is
10,000 kbps on SmartPath APs that do not support the IEEE 802.11n standard and 50,000 kbps on SmartPath APs that do.
However, you do not set the maximum rate (54,000 or 1,000,000 kbps, depending on the SmartPath AP model that you are con-
figuring) to ensure that streaming media does not consume all available bandwidth even if it is available.
Class 3 (e-mail)
Forwarding: WRR with a weight of 60
To help ensure that e-mail traffic remains flowing even when other types of data traffic compete with it for available bandwidth,
you elevate its priority by mapping SMTP and POP3 traffic to Class 3 and giving that class a higher weight (60) than the weight
for Class 2 traffic (30).
Maximum traffic rate for all Class 3 traffic: 54,000 or 1,000,000 kbps (the default, depending on the SmartPath AP)
NOTE: The SmartPath AP assigns all traffic that you do not specifically map to a class to Class 2, which by default uses WRR with a
weight of 30 and a rate of 54,000 or 1,000,000 kbps, depending on the SmartPath AP.
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