ZyXEL Communications ZyXEL ZyAIR NWA-3500 - Manual (Page 91)

Chapter 6 Wireless Configuration
ZyXEL NWA-3500 User’s Guide
91
The following table shows how priorities are assigned for packets coming from the LAN to the
WLAN.
6.3.3.2 ATC+WMM from WLAN to LAN
ATC+WMM from WLAN to LAN automatically prioritizes (assigns an ATC value to) all
packets coming from the WLAN. Packets are assigned an ATC value based on their WMM
value, not their size.
The following table shows how priorities are assigned for packets coming from the WLAN to
the LAN when using ATC+WMM.
6.3.4 Type Of Service (ToS)
Network traffic can be classified by setting the ToS (Type Of Service) values at the data source
(for example, at the ZyXEL Device) so a server can decide the best method of delivery, that is
the least cost, fastest route and so on.
6.3.4.1 DiffServ
DiffServ is a class of service (CoS) model that marks packets so that they receive specific per-
hop treatment at DiffServ-compliant network devices along the route based on the application
types and traffic flow. Packets are marked with DiffServ Code Points (DSCPs) indicating the
level of service desired. This allows the intermediary DiffServ-compliant network devices to
handle the packets differently depending on the code points without the need to negotiate paths
or remember state information for every flow. In addition, applications do not have to request
a particular service or give advanced notice of where the traffic is going.
6.3.4.2 DSCP and Per-Hop Behavior
DiffServ defines a new DS (Differentiated Services) field to replace the Type of Service (TOS)
field in the IP header. The DS field contains a 2-bit unused field and a 6-bit DSCP field which
can define up to 64 service levels. The following figure illustrates the DS field.
Figure 48 DiffServ: Differentiated Service Field
Table 17 ATC + WMM Priority Assignment (LAN to WLAN)
PACKET SIZE (BYTES) ATC VALUE WMM VALUE
1 ~ 250 ATC_High WMM_VIDEO
250 ~ 1100 ATC_Medium WMM_BEST_EFFORT
1100 + ATC_Low WMM_BACKGROUND
Table 18 ATC + WMM Priority Assignment (WLAN to LAN)
WMM VALUE ATC VALUE
WMM_VOICE ATC_High
WMM_VIDEO ATC_High
WMM_BEST_EFFORT ATC_Medium
WMM_BACKGROUND ATC_Low
NONE ATC_Medium
DSCP
(6-bit) Unused
(2-bit)