User guide

E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
9-15
T
RAFFIC
G
ROUPINGS AND
C
REATING A
Q
O
S P
OLICY
802.1p priority information is replaced according to the hardware queue that is used when
transmitting from the switch. The mapping is described in Tab le 9 -8 for switches based on
the “i” chipset and for other Extreme switches. This mapping cannot be changed.
C
ONFIGURING
D
IFF
S
ERV
Contained in the header of every IP packet is a field for IP Type of Service (TOS), now
also called the DiffServ field. The TOS field is used by the switch to determine the type
of service provided to the packet.
Observing DiffServ code points as a traffic grouping mechanism for defining QoS
policies and overwriting the Diffserv code point fields are supported in switches using
the “i” chipset.
Figure 9-2 shows the encapsulation of an IP packet header.
Table 9- 8: Queue to 802.1p Priority Replacement Value
Hardware Queue
Summit Chipset
Hardware Queue
“ i ” Chipset
802.1p Priority
Replacement Value
Q0 Q0
0
Q1
1
Q1 Q2 2
Q3 3
Q2 Q4 4
Q5 5
Q3 Q6 6
Q7 7