User guide

3-48 Packet Over SONET Module Installation and User Guide
Configuring the PoS Module
DiffServ Classification
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. The examination of DiffServ
information is disabled by default. To enable examination of DiffServ information, use
the command:
enable diffserv examination ports [<portlist> | all]
Changing DiffServ Code Point Assignments in the QoS Profile
Because the 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 3-8.
To configure the mapping between a DiffServ code point and a specified QoS profile,
use the following command:
config diffserv examination code-point <code_point>
qosprofile <qosprofile> ports <portlist>
{low-drop-probability | high-drop-probability}
The mapping is applied in the ingress direction—for IP packets received from the
SONET link.
Table 3-8: 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