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Chapter 11 Quality of Service (QoS)
P-660RU-Tx v3 User’s Guide
104
11.3 QoS Technical Reference
This section provides some technical background information about the topics covered in this
chapter.
11.3.1 IEEE 802.1p
IEEE 802.1p specifies the user priority field and defines up to eight separate traffic types. The
following table describes the traffic types defined in the IEEE 802.1d standard (which
incorporates the 802.1p).
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.
802.1p This is the 802.1p priority level.
Actions
IPP/TOS (DSCP)
Remarking
The ZyXEL Device re-assigns the priority values specified in this field to
matched traffic.
802.1p Remarking The ZyXEL Device re-assigns the priority levels specified in this field to
matched traffic.
Queue # The ZyXEL Device assigns the queue level specified in this field to matched
traffic.
Table 28 Advanced Setup > QoS > QoS Settings Summary (continued)
LABEL DESCRIPTION
Table 29 IEEE 802.1p Priority Level and Traffic Type
PRIORITY
LEVEL
TRAFFIC TYPE
Level 7 Typically used for network control traffic such as router configuration messages.
Level 6 Typically used for voice traffic that is especially sensitive to jitter (jitter is the variations in
delay).
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.