TP-Link TL-SL3428 Switch User Manual


 
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Section 12. Conguring Quality of Service
This section contains the following topics:
Quality of Service Overview
Enabling Quality of Service
Mapping Queues
12.1 Quality of Service Overview
Network trafc is usually unpredictable, and the only basic assurance that can be offered is best effort trafc delivery. To
overcome this challenge, Quality of Service (QoS) is applied throughout the network. This ensures that network trafc is
prioritized according to specied criteria, and that specic trafc receives preferential treatment. QoS in the network optimizes
network performance and entails two basic facilities:
Classifying incoming trafc into handling classes, based on an attribute, including:
– The ingress interface
– Packet content
– A combination of these attributes
Providing various mechanisms for determining the allocation of network resources to different handling classes, including:
– The assignment of network trafc to a particular hardware queue
– The assignment of internal resources
– Trafc shaping
In this document, the terms Class of Service (CoS) and QoS are used in the following context:
CoS provides varying Layer 2 trafc services. CoS refers to classication of trafc to trafc-classes, which are handled as
an aggregate whole, with no per-ow settings. CoS is usually related to the 802.1p service that classies ows according
to their Layer 2 priority, as set in the VLAN header.
QoS refers to Layer 2 trafc and above. QoS handles per-ow settings, even within a single trafc class.
The QoS facility involves the following elements:
Trafc Classication — Classies each incoming packet as belonging to a given trafc class, based on the packet
contents and/or the context.
Assignment to Hardware Queues — Assigns incoming packets to forwarding queues. Packets are sent to a particular
queue for handling as a function of the trafc class to which they belong, as dened by the classication mechanism.
Trafc Class-Handling Attributes — Applies QoS/CoS mechanisms to different classes, including:
– Bandwidth Management
– Shaping/ Rate Limiting
– Policing
12.1.1 Mapping to Queues
Queues are used in both Basic and Advanced QoS modes. Default settings are applied to maps in Service QoS mode. A
Trust Behavior can be selected, or the output service elds can be selected, including:
VLAN Priority Tags (VPT) — VPTs are mapped to an output queues based on the VPT. While queue mapping is user-
dened, the VPT default mapping to the output queue is as follows. In the VPT default mapping, Queue 1 has the lowest
priority.