Deployment Guide
81
E
XAMPLE
4: A
PPLYING
Q
O
S
In this example, you want the hive members to prioritize voice, streaming media, and e-mail traffic. First, you map
distinguishing elements of these traffic types to three Aerohive QoS (Quality of Service) classes:
Class 6:
voice traffic from VoIP phones with MAC OUI 00:12:3b (the OUI for all phones in the network)
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 used
—
a good approach for setting its rate is to calculate
the bandwidth necessary for a limited number of voice calls 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 MMS (Microsoft Media Server) 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 hive members map the traffic matching these profiles that arrives at these
interfaces to the proper Aerohive classes.
You next define a QoS policy that defines how the hive members prioritize and process the traffic mapped to
Aerohive classes 6, 5, and 3. The QoS policy (named "voice") is shown in
Figure 4 on page 82
and has these settings:
Class 6 (voice)
Forwarding: strict (Hive members forward traffic mapped to this class immediately without queuing it.)
Maximum rate for all class 6 traffic: 512 Kbps, which supports eight concurrent 64-Kbps VoIP calls:
512 Kbps maximum rate
÷
64 Kbps/call = 8 calls maximum (more if the codec provides greater compression)
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 increase the bandwidth available for streaming media when there is no competition for it (the
default rate for class 5 is 10,000 Kbps). However, you do not set the maximum rate (54,000 Kbps) 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 Kbps (the default)
