Chapter 7: Quality of Service (QoS)
QoS Overview
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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 820’s personalized QoS enables operators to handle a wide and diverse range of scenarios.
PTP 820’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 in 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.
shows the basic flow of PTP 820’s QoS mechanism. Traffic ingresses (left to right) via
the 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 139 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.
