Intel® Priority Packet Overview

Intel® Priority Packet is a utility that lets you set up priority filters to process high priority network traffic before normal traffic. Using Priority Packet, you can set up priority filters to give priority to time-critical traffic. You can set up global filters that apply to the entire system, or network-component-specific filters that apply only to specific network components (individual adapters, VLANs, or adapter teams). You can also create custom priority filters, or use priority filter templates to assign filter properties you use often. Priority Packet comes with pre-defined priority filter templates, or you can create your own templates.

Use Priority Packet filters to:

• Tag packets with priority levels or forwarding behaviors
• Drop incoming packets that match certain criteria
• Count the number of packets that match certain criteria

Priority Packet is available on the Intel CD.

Intel's Priority Packet lets you set up priority filters to send packets on the network with an indicated priority or forwarding behavior. By prioritizing traffic at the hosts or entry point of the network, network devices can base forwarding decisions on priority information defined in the packet.

Priority Packet prioritizes traffic based on priority filters—parameters you assign to packets. Using Priority Filter Wizard, you can set up filters from templates or define custom priority filters based on the following traffic filter types:

• Node (MAC) address/Ethertype
• TCP/IP information
• IPX information

Priority Packet provides the following methods for prioritizing traffic:

• IEEE 802.1p Tagging
• IP ToS (Type of Service) Layer 3 Tagging—supporting both Differentiated Services Codepoint (DSCP) and Legacy IP Precedence
• Intel High Priority Queue

IEEE 802.1p is an IEEE standard for tagging (or adding additional bytes of information to) packets with different priority levels. Packets are tagged with four additional bytes, that indicate a priority level. Tags also increase the packet size. When these packets are sent out on the network, the higher priority packets are transferred first by IEEE 802.1p-aware devices. Priority packet tagging (also known as Traffic Class Expediting) allows the adapter to work with other components of the network (switches, routers) to deliver packets based on priority level. Using Priority Packet, 802.1p tagging lets you assign specific priority levels from 0 (low) to 7 (high).

CAUTION: IEEE 802.1p tagging increases the size of the packets. Some hubs and switches will not recognize the larger packets because they exceed the maximum frame size of standard Ethernet packets and will drop them. Check your hub or switch documentation to see if it supports 802.1p. (You can configure the switch to strip the tags from the packets and send them on to the next destination as normal traffic.) If these devices do not support 802.1p or you are unsure, use High Priority Queue 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 Intel® PRO/100+ server adapters support 802.1p. Intel® PRO/100B adapters do not.

To assign a IEEE 802.1p, you can specify it using Priority Packet when you create or assign a priority filter.

IP ToS Layer 3 Tagging

Priority Packet supports two Type of Service (ToS) tagging methods: 

• Differentiated Services Codepoint (DSCP)
• Legacy IP Precedence

Differentiated Services Codepoint (DSCP) is a new tagging method that classifies packets based on network policies and rules, not on priority. The tags assign one of 64 possible forwarding behaviors known as per hop behaviors (PHBs). A PHB provides a particular service level (bandwidth, queuing, and dropping decisions) in accordance with network policy. Using Priority Packet, DSCP tagging lets you assign assured forwarding (AF) codepoints, using one of four AF classes and one of three drop precedence values. You may also enter your own non-standard codepoints.

DSCP tags replace the existing IP header, and do not add any additional bytes to packets. DSCP tags are backwards compatible with legacy ToS IP precedence bits; so non-DSCP compliant, ToS-enabled devices will not conflict with the DSCP mapping. A default DSCP mapping to "best effort" forwarding will be applied if network rules are not defined or the devices are non-DSCP compliant.

To assign DSCP, you can specify it using Priority Packet when you create or assign a priority filter for IP traffic.

For more information on DSCP, see RFC 2474 and 2475 on the IETF (Internet Engineering Task Force) Web site.

Legacy IP Precedence is an early tagging method that classifies and prioritizes packets. When these packets are sent out on the network, the higher priority packets are transferred first. Using Priority Packet, Legacy IP Precedence tagging lets you assign the following specific priority levels:

Network Control = 111 (7 in binary)
Internet Control = 110 (6 in binary)
CRITIC/ECP = 101 (5 in binary)
Flash Override = 100 (4 in binary)
Flash = 011 (3 in binary)
Immediate = 010 (2 in binary)
Priority = 001 (1 in binary)
Routine = 000 (0 in binary)

To assign a Legacy IP Precedence, you can specify it using Priority Packet when you create or assign a priority filter.

If your network infrastructure devices do not support IEEE 802.1p or IP ToS, or you are unsure, you can still define priority filters and transmit packets from the adapter onto the network as high priority. While High Priority Queue (HPQ) does not provide the precise priority levels of 802.1p and IP ToS 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 packets from the application with a priority filter are sent out first. HPQ does not change network routing, nor does it add any information to the packets.

To assign HPQ, you can specify it using Priority Packet when you create or assign a priority filter.

If you add an adapter to a team, its filters are removed automatically from the adapter. When you apply HPQ tagging to a team, you assign HPQ tagging to all adapters in the same team, including any new ones subsequently added.

For more information, see the related white paper on Intel's networking Web site.

Dropping Incoming Packets

At times, as an administrator, you may wish to drop (squelch) malicious or otherwise unwanted packets that come into your computer. You can use Priority Packet to specify that incoming packets of a certain type should be dropped.

Counting Incoming or Outgoing Packets

You can use Priority Packet to specify that you want all incoming or outgoing packets of a certain type to be counted. This allows you to monitor, or track, specific types of packets.

The adapter lines and operating systems supported by Priority Packet II include:

* To use Priority Packet II with Windows 98 or Windows Millenium, you must first enable remote DCOM connectivity on your system. For more information, visit the Microsoft web site at: http://www.microsoft.com/com/tech/dcom.asp

NOTE: Priority Packet II does not support Windows 95. Priority Packet II only runs on systems having Intel adapters installed. You cannot set filters for non-Intel remote adapters.