Intel IXP400 manual Priority to Traffic Class Mapping, QoS on Receive for Untagged Frames

Intel® IXP400 Software

Access-Layer Components: Ethernet Database (IxEthDB) API

Traffic class for untagged frames (unexpedited traffic) is automatically selected from the default traffic class associated with the port. The default port traffic class is computed from the default port 802.1Q tagging information, configured as described in “Ingress Tagging and Tag Removal” on page 165. The first three bits from the default 802.1Q tag constitute the default port user priority, which is mapped using the priority mapping table to obtain the default port traffic class.

Figure 57. QoS on Receive for Untagged Frames

			Rx
Incoming frame (untagged)
Preamble	Start frame	Dest MAC addr	Src MAC addr	Len	Data	Pad	FCS
	Traffic class queue selector
	Default port traffic
	class
			Traffic class 0 queue
			Traffic class 1 queue
					Traffic class 2 queue
						Traffic class 3 queue
	EthDB				EthAcc

Note: In order to use Receive QoS processing, IxEthAcc must be configured to operate in Receive FIFO Priority Mode. Refer to Section 9.5.3.2.

10.3.5.3Priority to Traffic Class Mapping

In order to associate the mapping of a frames 802.1Q priority value to the receive traffic class, the IxEthDB API maintains a Priority Mapping Table. Functions are provided to modify individual priority mapping entries, or to define a completely new table definition.

Programmer’s Guide	IXP400 Software Version 2.0	April 2005
	Document Number: 252539, Revision: 007	171