Configuring Diffserv - Extreme Networks BlackDiamond 6800 Installation And User Manual

Also note that, in all cases, the 802.1p priority bits of ingress frames forwarded to the
switch backplane are set based on the ingress QoS profile classification. More
specifically, the 802.1p priority value is set to qp# – 1. For example, if the packet is
classified to qp5, then the 802.1p priority value is set to 4.

Configuring DiffServ

All of the existing ExtremeWare DiffServ commands are supported by ATM ports with
IP frames that are encapsulated for bridged or routed protocols. ATM ports also support
a DiffServ code point (DSCP) mapping function that you configure using the
config diffserv dscp-mapping
6-bit value in the IP-TOS byte of the IP packet header. For more information on DSCPs,
see "Configuring DiffServ" in the ExtremeWare Software User Guide.
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
values are grouped and assigned to the default QoS profiles listed in
Table 3-9: Default Code Point-to-QoS Profile Mapping
Code Point
0-7
8-15
16-23
24-31
32-39
Asynchronous Transfer Mode (ATM) Module Installation and User Guide
command, which is described below. The DSCP is a
QoS Profile
Qp1
Qp2
Qp3
Qp4
Qp5
Configuring QoS Functions
6 = 64). By default, the
Table 3-9.
3-33