Extreme Networks ExtremeWare 7.2e, Инструкция по установке и эксплуатации

Страница: 117 / 344

Traffic Groupings
ExtremeWare 7.2e Installation and User Guide 117
Configuring 802.1p Priority For Slow Path Traffic
Some traffic can originate on the switch, for example Ping or Telnet packets. This traffic comes from the
switch CPU and is referred to as slow path traffic. This traffic is internally tagged with an 802.1p
priority of 7, by default, and egresses the VLAN through the highest queue. If you want to set a
different tag (and priority) use the following command to set the priority to a number between 0 and 7:
configure vlan <vlan name> priority <priority>
Other traffic transported across the switch and VLAN will not be changed, in other words, the 802.1p
values will not be affected by the VLAN priority setting.
Replacing 802.1p Priority Information
By default, 802.1p priority information is not replaced or manipulated, and the information observed on
ingress is preserved when transmitting the packet. This behavior is not affected by the switching or
routing configuration of the switch.
However, the switch is capable of replacing the 802.1p priority information. To replace 802.1p priority
information, you will use an access list to set the 802.1p value. See “IP Access Lists (ACLs)” on
page 142, for more information on using access lists. You will use the
set dot1p <dot1p_value>
parameter of the
create access-list
command to replace the value. The packet is then placed on the
queue that corresponds to the new 802.1p value.
Configuring DiffServ
Contained in the header of every IP packet is a field for IP Type of Service (TOS), now also called the
DiffServ field. The TOS field is used by the switch to determine the type of service provided to the
packet.
Observing DiffServ code points as a traffic grouping mechanism for defining QoS policies and
overwriting the Diffserv code point fields are supported.
Figure 19 shows the encapsulation of an IP packet header.
6 Qp7
7 Qp8
Table 24: 802.1p Priority Value-to-QoS Profile Default Mapping (Continued)
Priority Value QoS Profile