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for prioritizing traffic: IEEE 802.1p tagging and High Priority
Queue.
IEEE 802.1p is a new IEEE standard for tagging, or adding
additional bytes of information to packets with different prior-
ity levels. Packets are tagged with 4 additional bytes, which
increase the packet size and indicate a priority level. When
you send these packets out on the network, the higher prior-
ity packets are transferred first. Priority packet tagging (also
known as Traffic Class Expediting) allows the adapter to
work with other elements of the network (such as switches
and routers) to deliver priority packets first. You can assign
specific priority levels from 0 (low) to 7 (high).
You can assign values to packets based on their priority
when you use the IEEE 802.1p standard for packet tagging.
This method requires a network infrastructure that supports
packet tagging. The routing devices receiving and transfer-
ring these packets on the network must support 802.1p for
tagging to be effective.
After you set up the priority filter in Priority Packet, you must
launch IBMSet and select 802.1p/802.1Q Tagging on the
Advanced tab.
Note: IEEE 802.1p tagging increases the size of the pack-
ets it tags. Some hubs and switches will not recog-
nize the larger packets and will drop them. Check the
hub or switch documentation to see if they support
802.1p. (You can configure the switch to strip the
tags from the packets and send it on to the next desti-
nation as normal traffic.) If these devices do not sup-
port 802.1p or if you are not sure, use High Priority
Queue (HPQ) to prioritize network traffic.
The requirements for effectively using IEEE 802.1p tagging
are:
• The other devices receiving and routing 802.1p tagged
packets must support 802.1p.
• The adapters on these devices must support 802.1p.
The Ethernet controller in the Netfinity 3500 M20 and
all IBM Netfinity 10/100 Ethernet Security Adapters
support 802.1p.
• The adapter cannot be assigned to an adapter team.
• If you are setting up VLANs and packet tagging on the
same adapter, 802.1p/802.1Q Tagging must be
enabled on the IBMSet Advanced tab.
If the network infrastructure devices do not support IEEE
802.1p or you are not sure, you can still define filters and
send packets as high priority. While High Priority Queue
(HPQ) does not provide the precise priority levels of 802.1p
tagging, it does assign traffic as either high or low priority
and sends high priority packets first. Therefore, if there are
multiple applications on a system sending packets, the pack-
ets from the application with a filter are sent out first. HPQ
does not change network routing, nor does it add any infor-
mation to the packets.