Port-Based Qos; Ieee 802.1P Qos - ZyXEL Communications GS1200 Series User Manual

12.2.1 Port-Based QoS

The Port-Based QoS feature assigns priority to data transmitted through a particular port. When the data
arrives to a port it begins a queue. Therefore the Switch has a queue for each port. If data arrives at the
same time to all ports, ports with higher priority will be first to transmit the data received. The higher the
priority of the port, the less delays the data passing through will have.

12.2.2 IEEE 802.1p QoS

IEEE 802.1p defines a 3-bit field called PCP (Priority Code Point) within the IEEE 802.1Q VLAN tag, which is
also referred to as a CoS (Class of Service) value and indicates the frame priority level. IEEE 802.1p QoS
uses the priority value (from 0 to 7) to define up to eight traffic types. That is, each priority level defines a
class of service. The table below shows the IEEE recommendations for traffic types, these may vary or be
reassigned.
Table 12 IEEE Priority to Traffic Type Mapping Recommendations
PCP PRIORITY
1 0 (lowest)
0 1 (default)
2 2
3 3
4 4
5 5
6 6
7 7 (highest)
Note: Frames without an explicit priority tag are treated as system traffic and assigned to
Queue0.
Figure 43 IEEE 802.1p QoS
ACRONYM TRAFFIC TYPES
BK Background
BE Best Effort
EE Excellent Effort
CA Critical Applications
VI Video, < 100 ms latency and jitter
VO Voice, < 10 ms latency and jitter
IC Internetwork Control
NC Network Control
GS1200 Series User's Guide
58