ZyXEL P-660HN-51 User Guide - Page 177

Chapter 14 Quality of Service (QoS) Table 60 IEEE 802.1p Priority Level and Traffic Type PRIORITY LEVEL TRAFFIC TYPE 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. 14.3.2 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 eightbit 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. 14.3.3 Automatic Priority Queue Assignment If you enable QoS on the ZyXEL Device, the ZyXEL Device 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 ZyXEL Device. On the ZyXEL Device, traffic assigned to higher priority queues gets through faster while traffic in lower index queues is dropped if the network is congested. Table 61 Internal Layer2 and Layer3 QoS Mapping LAYER 2 LAYER 3 PRIORITY QUEUE 0 1 2 IEEE 802.1P USER PRIORITY (ETHERNET PRIORITY) 1 2 0 TOS (IP PRECEDENCE) DSCP 0 000000 0 000000 IP PACKET LENGTH (BYTE) >1100 P-660HN-TxA User's Guide 177