User guide

E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
9-17
T
RAFFIC
G
ROUPINGS AND
C
REATING A
Q
O
S P
OLICY
O
BSERVING
D
IFF
S
ERV
I
NFORMATION
When a packet arrives at the switch on an ingress port, the switch examines the first six
of eight TOS bits, called the code point. The switch can assign the QoS profile used to
subsequently transmit the packet based on the code point. The QoS profile controls a
hardware queue used when transmitting the packet out of the switch, and determines
the forwarding characteristics of a particular code point. Viewing DiffServ information
can be enabled or disabled; by default it is disabled. To view DiffServ information, use
the command:
enable diffserv examination ports [<portlist> | all]
CHANGING DIFFSERV CODE POINT ASSIGNMENTS IN THE Q0S PROFILE
Because the code point uses six bits, it has 64 possible values (2
6
= 64). Be default, the
values are grouped and assigned to the default QoS profiles listed in Ta ble 9 -1 0.
enable diffserv examination ports [<portlist> |
all]
Enables the diffserv field of an ingress IP packet
to be examined by the switch in order to select a
QoS profile. The default setting is disabled.
enable diffserv replacement ports [<portlist> |
all]
Enables the diffserv code point to be overwritten
in packets transmitted by the switch. Eight
user-defined code points can be configured on
each port. The 802.1P priority bits (3-bits) are
used to select one of the eight code points. The
default setting is disabled.
unconfig diffserv examination ports [<portlist>
| all]
Removes the diffserv examination code point
from a port.
unconfig diffserv replacement ports [<portlist>
| all]
Removes the diffserv replacement mapping from
a port.
Table 9-10: Default Code Point-to-QoS Profile Mapping
Code Point QoS Profile
0-7 Qp1
8-15 Qp2
16-23 Qp3
24-31 Qp4
Table 9- 9: DiffServ Configuration Commands (continued)
Command Description