Extreme Networks ExtremeWare XOS 11.1, Руководство пользователя

Страница: 209 / 496

Traffic Groupings
ExtremeWare XOS 11.1 Concepts Guide
209
at each switch location. Another advantage is that endstations can perform their own packet marking
on an application-specific basis. Extreme Networks switch products have the capability of observing
and manipulating packet marking information with no performance penalty.
The documented capabilities for 802.1p priority markings or DiffServ capabilities (if supported) are not
impacted by the switching or routing configuration of the switch. For example, 802.1p information can
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
Extreme Networks switches support the standard IEEE 802.1p priority bits that are part of a tagged
Ethernet packet. The 802.1p bits can be used to prioritize the packet and to assign that packet to a
particular QoS profile.
When a tagged packet arrives at the switch, the switch examines the 802.1p priority field and maps the
packet to a specific queue when subsequently transmitting the packet. 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 .
Figure 10: Ethernet packet encapsulation
Observing 802.1p information. When ingress traffic that contains 802.1p prioritization information is
detected by the switch, that traffic is mapped to various queues on the egress port of the switch. The
BlackDiamond 10K switch supports 9 hardware queues by default; you can modify the characteristics of
each queue. By default, the Aspen 8810 switch supports 2 queues based on flows; you can define up to
6 additional queues. The transmitting queue determines the characteristics used when transmitting
packets.
To control the mapping of 802.1p prioritization values to 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 shown in
Table 34 .
Table 34: Default 802.1p priority value-to-QoS profile mapping
Priority Value
BlackDiamond 10K Switch
Default QoS Profile Aspen 8810 Switch Default QoS
Profile
0 QP1 QP1
1 QP2 QP1
EW_024
Source
address
802.1Q
type
802.1p
priority
802.1Q
VLAN ID
IP packet CRC
Destination
address
8100