Specifications

88 ExtremeWare XOS 10.1 Concepts Guide
Quality of Service (QoS)
Figure 9: IP packet header encapsulation
Observing DiffServ Information
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 following command:
show diffserv
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 Table 15.
Table 15: Default 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