Priority - Zhone zNID-GPON-2402 Configuration Manual

Priority

The system can be configured to prioritize traffic based on either the layer 2
VLAN CoS bits or the layer 3 ToS bits. The prioritization method is selected
on the VLAN Mode page as shown below.
Figure 167: VLAN modes
The zNID 24xx products support the prioritization of traffic based on either
the ToS (Type of Service) values in IP packets or CoS (Class of Service)
values in Ethernet VLAN headers as defined by IETF RFC1349 and IEEE
802.1p respectively. The configured ToS or CoS levels specify packet priority
and queuing used to transport the packet through the Ethernet and IP
networks.
CoS
The VLAN header in Ethernet packets contains a CoS field for queuing
priority or Class of Service (CoS) values based on eight (0-7) levels of
service, with the lowest priority being 0 and the highest priority 7.
The eight priority values are mapped to 4 queues. The highest priority queue
(Critical) uses strict priority. All the packets in that queue will be sent before
any packets in the other queues. If there is a large amount of data in the strict
priority queue, it is possible that the lower priority queues never get serviced.
A weighted round robin approach is used for the remaining queues. The
packets are sent in a ratio of 16 high priority, 8 Medium, and 4 Low priority.
Table 58: CoS value to priority mapping
CoS Value Priority Queue
0 Low
1 Low
2 Med
3 Med
4 High
Priority Method
WRR 16/8/4 (weight = 4)
WRR 16/8/4 (weight = 4)
WRR 16/8/4 (weight = 8)
WRR 16/8/4 (weight = 8)
WRR 16/8/4 (weight = 16)
zNID 24xx Series Configuration Guide
VLANS
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