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IEEE 802.1p Tagging
IEEE 802.1p is a new IEEE standard for tagging, or adding additional bytes of
information to, packets with different priority levels. Packets are tagged with 4
additional bytes, which increase the packet size and indicate a priority level.
When these packets are sent out on the network, the higher priority packets are
transferred first. Priority packet tagging (also known as Traffic Class Expedit-
ing) allows the adapter to work with other elements of the network (switches,
routers) to deliver priority packets first. 802.1p tagging enables you to assign
specific priority levels from 0 (low) to 7 (high).
Using the IEEE_802.1p standard for packet tagging, you can assign values to
packets based on their priority. This method requires a network infrastructure
that supports packet tagging. The routing devices receiving and transferring
these packets on your network must support 802.1p for tagging to be effective.
After you set up the priority filter in Priority Packet, you must launch Intel
PROSet and select ‘802.1p/802.1Q Tagging’ on the Advanced tab.
CAUTION: IEEE 802.1p tagging increases the size of the packets it
tags. Some hubs and switches won’t recognize the larger packets and
will drop them. Check your 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 destination as normal traffic.) If these
devices don’t support 802.1p or you’re 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 (adapters using the Intel
82558 or later Ethernet controller). All PRO/100+ adapters support 802.1p.
PRO/100B adapters do not.
• The adapter(s) cannot be assigned to an adapter team.
• If you’re setting up VLANs and packet tagging on the same adapter, the
‘802.1p/802.1Q Tagging’ must be ‘Enabled’ on the Intel PROSet
Advanced tab.
Intel High Priority Queue
If your network infrastructure devices don’t support IEEE 802.1p or you’re not
sure, you can still define filters and send packets as high priority. While High
Priority Queue (HPQ) doesn’t provide the precise priority levels of 802.1p tag-
ging, 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 packets from the application with a filter are sent out first. HPQ
doesn't change network routing, nor does it add any information to the packets.
P100se~2.fm Page 17 Tuesday, January 5, 1999 10:04 AM
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