Alteon Application Switch Operating System Application Guide
Filtering and Traffic Manipulation
376 Document ID: RDWR-ALOS-V2900_AG1302
Filtering on 802.1p Priority Bit in a VLAN Header
Alteon lets you filter based on the priority bits in a packet's VLAN header. The priority bits are
defined by the 802.1p standard within the IEEE 802.1Q VLAN header. The 802.1p bits, if present in
the packet, specify the priority that should be given to packets during forwarding. Packets with
higher (non-zero) priority bits should be given forwarding preference over packets with numerically
lower priority bit value.
802.1p Priorities
The IEEE 802.1p standard uses eight levels of priority, 0 through 7, with priority 7 being assigned to
highest priority network traffic such as OSPF or RIP routing table updates, priorities 5 though 6
being for delay-sensitive applications such as voice and video, and lower priorities for standard
applications. A value of zero indicates a "best effort" traffic prioritization, and this is the default
when traffic priority has not been configured on your network. Alteon can only filter packets based
on the 802.1p values already present in the packets. It does not assign or overwrite the 802.1p
values in the packet.
Classifying Packets Based on 802.1p Priority Bits
Traffic is easily classified based on its 802.1p priority by applying a filter based on the priority bit
value. The Filtering Advanced menu provides the option to filter based on the priority bit value. The
filter matches if it finds the corresponding 802.1p bit value in the packet. If the packet does not
have the 802.1p bits, the filter does not match.
To configuring a filter to classify traffic
1. Configure a filter and an action.
2. Go to the Filtering Advanced menu and select the 802.1p priority value.
Apply a Bandwidth Management (BWM) contract to the prioritized filter. You can apply an
802.1p-prioritized filter to a BWM contract to establish the rule for how the traffic that matches
the defined 802.1p priority value. For more information on configuring a BWM contract, see
Contracts, page 761
.
>> SLB Port 10# add 3
(Add Filter 3 to SLB Port 10)
>> SLB Port 10# add 2048
(Add Filter 2048 to SLB Port 10)
>> # /cfg/slb/filt <x> /ena
(Enable the filter)
>> Filter 1 # action allow
(Set filter action)
>> # /cfg/slb/filt <x>
>> Filter <x># adv/8021p/
(Select the 802.1p advanced menu)
>> 802.1p Advanced# match ena
(Enable matching of 802.1p value)
>> # 802.1p Advanced# value 1
(Set the 802.1p priority value to match)
>> # /cfg/slb/filt <x> /adv/cont 1
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