Cambium Networks PTP 820 Series, User Manual, Page: 413 / 1149

Chapter 7: Quality of Service (QoS) QoS Overview
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Page 7-2
QoS Overview
Quality of Service (QoS) deals with the way frames are handled within the switching fabric. QoS is required in order
to deal with many different network scenarios, such as traffic congestion, packet availability, and delay
restrictions.
PTP 820G and PTP 820F ’s personalized QoS enables operators to handle a wide and diverse range of scenarios. PTP
820G and PTP 820F ’s smart QoS mechanism operates from the frame’s ingress into the switching fabric until the
moment the frame egresses via the destination port.
QoS capability is very important due to the diverse topologies that exist i n today’s network scenarios. These can
include, for example, streams from two different ports that egress via single port, or a port-to-port connection that
holds hundreds of services. In each topology, a customized approach to handling QoS will provide the best results.
Figure 213 shows the basic flow of PTP 820G and PTP 820F ’s QoS mechanism. Traffic ingresses (left to right) via th e
Ethernet or radio interfaces, on the “ingress path.” Based on the services model, the system determines how to
route the traffic. Traffic is then directed to the most appropriate output queue via the “egress path.”
Figure 213 QoS Block Diagram
(Optional)
Egress
Port
Scheduler/
Shaper
Standard QoS/ H-QoS
Queue
Manager
Marker
(Optional)
Egress
Port
Scheduler/
Shaper
Standard QoS/ H-QoS
Queue
Manager
Marker
(Optional)
Egress
Port
Scheduler/
Shaper
Standard QoS/ H-QoS
Queue
Manager
Marker
CET/Pipe
Services
Rate Limit
(Policing)
Classifier
(Optional)
Ingress
Port
Rate Limit
(Policing)
Classifier
(Optional)
Ingress
Port
Rate Limit
(Policing)
Classifier
(Optional)
Ingress
Port
GE/Radio
GE/Radio
GE/Radio
GE/Radio
GE/Radio
GE/Radio
The ingress path consists of the following QoS building blocks:
•
Ingress Classifier – A hierarchical mechanism that deals with ingress traffic on three different levels: interface,
service point, and service. The classifier determines the exact traffic stream and associates it with the
appropriate service. It also calculates an ingress frame CoS and Color. CoS and Color classification can be
performed on three levels, according to the user’s configuration .
•
Ingress Rate Metering – A hierarchical mechanism that deals with ingress traffic on three different levels:
interface, service point, and service point CoS. The rate metering mechanism enables the system to measure
the incoming frame rate on different levels using a TrTCM standard MEF rate meter, and to determine
whether to modify the color calculated during the classification stage.
The egress path consists of the following QoS building blocks:
•
Queue Manager – This is the mechanism responsible for managing the transmission queues, utilizing smart
WRED per queue and per packet color (Green or Yellow).