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C H A P T E R 10 Quality of Service (QoS)
153
You can change the QoS profile assignment for all 64 code points.
Use this command:
configure diffserv examination code-point <code-
point> qosprofile <qosprofile> ports [<portlist>]
Once assigned, the rest of the switches in the network prioritize the
packet using the characteristics specified by the QoS profile.
Replacing DiffServ Code Points
You can configure the switch to change the DiffServ code point in
the packet prior to the packet being transmitted by the switch. This
is accomplished with no impact on switch performance.
The DiffServ code point value used in overwriting a packet is
determined by the 802.1p priority value. As described in the section
“Replacing 802.1p Priority Information,” the 802.1p priority value
is, in turn, determined by the hardware queue used when
transmitting a packet.
It is not necessary to receive or transmit 802.1Q tagged frames, only
to understand that the egress hardware queue, which also
determines the 802.1p priority value, can also be configured to
determine the DiffServ value if you want to replace the DiffServ
code points.
To enable the replacement of DiffServ code points you must enable
both 802.1p replacement and DiffServ replacement using these
commands:
enable dot1p replacement ports [<portlist> | all]
enable diffserv replacement ports [<portlist> |
all]
The default 802.1p priority value to code point mapping is
described in Table 10.10.