Luxul XMS-1024P - Manual (Page 138)

138
XMS-1024P
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LUX-UG-XMS-1024P Vers: 081314
Priority Mode
This Switch implements three Priority Modes based on Port, 802.1P and DSCP. By
default, the priority mode based on Port is enabled.
„
Port Priority
Port Priority is a property of the Port. After Port Priority is confi gured, the Data stream
will be mapped to the Egress Queues according to the CoS (Cost of Service) of the Port
and the Mapping relationship between CoS and Queues.
„
802.1P Priority
Figure 9-2 802.1Q frame
As shown in the fi gure above, each 802.1Q Tag has a PRI fi eld, comprising 3 bits. The
3-bit priority fi eld is 802.1P Priority with a range of 0-7. 802.1P Priority determines the
priority of the packets based on the PRI value. In the Switch, you can confi gure differ-
ent priority tags mapping to the corresponding priority levels. The Switch determines
which packets are sent with what Priority when forwarding packets. The Switch
processes untagged packets and Maps them to the default priority mode.
„
DSCP Priority
Figure 9-3 IP Datagram
As shown in the fi gure above, the ToS (Type of Service) in an IP header contains 8 bits.
The fi rst three bits indicate IP Precedence with a range of 0-7. RFC2474 re-defi nes the
ToS fi eld in the IP packet header which is called the DS fi eld. The fi rst six bits (bit 0-5)
of the DS fi eld indicate DSCP precedence with a range of 0-63. The last 2 bits (bit 6
and bit 7) are reserved. In the Switch, you can confi gure different DS Field Mappings to