Chapter 13: Configuring Quality Of Service - Linksys SFE1000P Administration Manual

Configuring Quality of Service
Network traffic is usually unpredictable, and the only basic assurance that can be offered is best
effort traffic delivery. To overcome this challenge, Quality of Service (QoS) is applied throughout the
network. This ensures that network traffic is prioritized according to specified criteria, and that
specific traffic receives preferential treatment. QoS in the network optimizes network performance
and entails two basic facilities:
• Classifying incoming traffic 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 traffic to a particular hardware queue
– The assignment of internal resources
– Traffic shaping
The terms Class of Service (CoS) and QoS are used in the following context:
• CoS provides varying Layer 2 traffic services. CoS refers to classification of traffic to traffic-
classes, which are handled as an aggregate whole, with no per-flow settings. CoS is usually
related to the 802.1p service that classifies flows according to their Layer 2 priority, as set in
the VLAN header.
• QoS refers to Layer 2 traffic and above. QoS handles per-flow settings, even within a single
traffic class.
The QoS facility involves the following elements:
• Access Control Lists (ACLs) — Used to decide which traffic is allowed to enter the system,
and which is to be dropped. Only traffic that meets this criteria are subject to CoS or QoS
settings. ACLs are used in QoS and network security.
• Traffic Classification — Classifies each incoming packet as belonging to a given traffic
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 traffic class to which
they belong, as defined by the classification mechanism.
• Traffic Class-Handling Attributes — Applies QoS/CoS mechanisms to different classes,
including: Bandwidth Management

Chapter 13: Configuring Quality of Service

SFE1000P Gigabit Ethernet Switch Administration Guide
Chapter
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