SonicWALL 5.8.1 Manuale Utente

If symptoms of such a scenario emerge (e.g. excessive retransmissions of low-priority traffic), 
it is recommended that you create a separate VPN policy for the high-priority and low-priority 
classes of traffic. This is most easily accomplished by placing the high-priority hosts (e.g. the 
VoIP network) on their own subnet. 

If you want to change the inbound mapping of DSCP tag 15 from its default 802.1p mapping of 
1 to an 802.1p mapping of 2, it would have to be done in two steps because mapping ranges 
cannot overlap. Attempting to assign an overlapping mapping will give the error DSCP range 
already exists or overlaps with another range. First, you will have to remove 15 from its 
current end-range mapping to 802.1p CoS 1 (changing the end-range mapping of 802.1p CoS 
1 to DSCP 14), then you can assign DSCP 15 to the start-range mapping on 802.1p CoS 2.

The primary objective of QoS Mapping is to allow 802.1p tags to persist across non-802.1p 
compliant links (e.g. WAN links) by mapping them to corresponding DSCP tags before sending 
across the WAN link, and then mapping from DSCP back to 802.1p upon arriving at the other 
side:

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