Specifications

Traffic Groupings
ExtremeWare XOS 11.0 Concepts Guide 115
Figure 9: IP packet header encapsulation
Observing DiffServ code points as a traffic grouping mechanism for defining QoS policies and
overwriting the Diffserv code point fields are supported.
Observing DiffServ information. When a packet arrives at the switch on an ingress port and this
feature is enabled, the switch examines the first six of eight TOS bits, called the DiffServ code point. The
switch can then assign the QoS profile used to subsequently transmit the packet based on the code
point. The QoS profile controls which hardware queue is used when transmitting the packet out of the
switch and determines the forwarding characteristics of a particular code point. Examining DiffServ
information can be enabled or disabled; by default it is enabled. To enable DiffServ examination, use the
following command:
enable diffserv examination port [<port_list> | all]
Because the DiffServ code point uses six bits, it has 64 possible values (2
6
= 64). By default, the values
are grouped and assigned to the default QoS profiles listed in Table 21.
Table 21: Default DiffServ code point-to-QoS profile mapping
Code Point QoS Profile
0-7 QP1
8-15 QP2
16-23 QP3
24-31 QP4
32-39 QP5
40-47 QP6
48-55 QP7
56-63 QP8
EW_023
Type-of-service
DiffServ code point
IHL
Data (variable)
0 bits 31
Options (+ padding)
Destination address
Source address
07654321
Total lengthVersion
ProtocolTime-to-live
Header checksum
FlagsIdentification Fragment offset