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Intel
®
NetStructure™ 480T Routing Switch User Guide
be preserved across a routed switch boundary and DiffServ code
points can be observed or overwritten across a Layer 2 switch
boundary.
Configuring 802.1p Priority
The switch supports the standard 802.1p priority bits that are part of
a tagged Ethernet packet. The 802.1p bits can be used to prioritize
the packet, and assign it to a particular QoS profile.
When a packet arrives at the switch, the 802.1p priority field is
examined, and can be mapped to a specific hardware queue for
subsequent transmission. The 802.1p priority field is located
directly following the 802.1Q type field, and preceding the 802.1Q
VLAN ID, as shown in Figure 10.1.
Figure 10.1: Ethernet packet encapsulation
Observing 802.1p Information
When ingress traffic that contains 802.1p prioritization information
is detected by the switch, the traffic is mapped to various hardware
queues on the egress port of the switch. The 480T routing switch
supports eight hardware queues. The hardware queues determine
the bandwidth-management and priority characteristics used when
transmitting packets.
To control the mapping of 802.1p prioritization values to hardware
queues, 802.1p prioritization values can be mapped to a QoS
profile. The default mapping of each 802.1p priority value to QoS
profile is described in Table 10.6.
480t_022
Source
address
802.1Q
type
802.1p
priority
802.1Q
VLAN ID
IP packet CRC
Destination
address
8100