ZyXEL Communications P-660HN-F1A, User Manual

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Chapter 16 Quality of Service (QoS)
P-660HN-F1A User’s Guide
271
DSCP is backward compatible with the three precedence bits in the ToS octet so
that non-DiffServ compliant, ToS-enabled network device will not conflict with the
DSCP mapping.
The DSCP value determines the forwarding behavior, the PHB (Per-Hop Behavior),
that each packet gets across the DiffServ network. Based on the marking rule,
different kinds of traffic can be marked for different kinds of forwarding. Resources
can then be allocated according to the DSCP values and the configured policies.
16.10.4 Automatic Priority Queue Assignment
If you enable QoS on the P-660HN-F1A, the P-660HN-F1A 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-660HN-F1A. On the P-660HN-F1A, traffic assigned to higher priority queues
gets through faster while traffic in lower index queues is dropped if the network is
congested.
DSCP (6 bits) Unused (2 bits)
Table 82 Internal Layer2 and Layer3 QoS Mapping
PRIORITY
QUEUE
LAYER 2 LAYER 3
IEEE 802.1P
USER PRIORITY
(ETHERNET
PRIORITY)
TOS (IP
PRECEDENCE)
DSCP
IP PACKET
LENGTH (BYTE)
0 1 0 000000
1 2
2 0 0 000000 >1100
3 3 1 001110
001100
001010
001000
250~1100
4 4 2 010110
010100
010010
010000