ZyXEL Communications P-660RU-Tx 11.3.2 IP Precedence, 11.3.3 Automatic Priority Queue Assignment

	Chapter 11 Quality of Service (QoS)
Table 29 IEEE 802.1p Priority Level and Traffic Type
PRIORITY	TRAFFIC TYPE
LEVEL
Level 5	Typically used for video that consumes high bandwidth and is sensitive to
	jitter.
Level 4	Typically used for controlled load, latency-sensitive traffic such as SNA
	(Systems Network Architecture) transactions.
Level 3	Typically used for “excellent effort” or better than best effort and would
	include important business traffic that can tolerate some delay.
Level 2	This is for “spare bandwidth”.
Level 1	This is typically used for non-critical “background” traffic such as bulk
	transfers that are allowed but that should not affect other applications and
	users.
Level 0	Typically used for best-effort traffic.

11.3.2 IP Precedence

Similar to IEEE 802.1p prioritization at layer-2, you can use IP precedence to prioritize packets in a layer-3 network. IP precedence uses three bits of the eight- bit ToS (Type of Service) field in the IP header. There are eight classes of services (ranging from zero to seven) in IP precedence. Zero is the lowest priority level and seven is the highest.

11.3.3 Automatic Priority Queue Assignment

If you enable QoS on the P-660RU-Tx, the P-660RU-Tx can automatically base on the IEEE 802.1p priority level, IP precedence and/or packet length to assign priority to traffic which does not match a class.

The following table shows you the internal layer-2 and layer-3 QoS mapping on the P-660RU-Tx. On the P-660RU-Tx, traffic assigned to higher priority queues gets through faster while traffic in lower index queues is dropped if the network is congested.

Table 30 Internal Layer2 and Layer3 QoS Mapping

	LAYER 2	LAYER 3
PRIORITY	IEEE 802.1P	TOS (IP		IP PACKET
QUEUE	USER PRIORITY		DSCP
	(ETHERNET	PRECEDENCE)		LENGTH (BYTE)
	PRIORITY)
0	1	0	000000
1	2
2	0	0	000000	>1100

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P-660RU-Tx User’s Guide