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Chapter 4
IP QoS Framework Overview
E-NIT-CTC-20041213-0013 v0.5
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4.1 Main Framework Components
Graphical overview The figure below shows a graphical overview of the main components in the
upstream datapath.Notice that there are two main blocks, the input and output.
In between these two blocks the IP packets go through a series of processes like
firewall, nat etc.
QoS Components The main QoS components are:
Resource Management: The main purpose of this module is to assure that
arriving low priority data cannot consume all the internal memory resources. In
case of congestion and resource starvation, this module will deny low priority
data from consuming memory resources. The Resource Management module
also maps the Layer 2 VLAN user priority to an internal Class.
Classification: The classification module classifies incoming data. Data that
matches the classification criteria will be labelled. A label is only of internal
significance and can be used in forwarding and QoS definition. Each label can
have an internal QoS class associated with it. Data will experience treatment
(queuing and scheduling) according to its QoS class. The SpeedTouch™
Business DSL Router support 16 internal classes which are linked to the 6
queues. The 6 queues are:
The Real Time queue (EF)
The Weight Fair queue 4 (WFQ4)
The Weight Fair queue 3 (WFQ3)
The Weight Fair queue 2 (WFQ2)
The Weight Fair queue 1 (WFQ1)
The Best Effort queue (BE)
IP Forwarding: IP forwarding supports the use of labels to forward classified
data to any IP interface. This allows, for example, to forward data based upon
port(-ranges), IP addresses, protocol, source interface, Differentiated Services
Code Point (DSCP), … (see the “Routing Configuration Guide” for more details
on routing and forwarding)
IP QoS Queuing, Scheduling and Rate Limiting: This module implements the
internal IP QoS queues and scheduling and maps the internal class (set during
classification or set by the Resource management module) to one of these
queues. Rate-limiting can be configured for the fixed priority real-time queue.
This queue has fixed priority over other queues. This ensures a low latency but
could lead to starvation of lower priority queues. By configuring a percentage of
the total available interface bandwidth, data from this queue will be limited to
this bandwidth in case of congestion.
ATM QoS: The ATM Quality of Service module holds the extensive ATM QoS
features, starting with per ATM VP/VC queuing and shaping, per ATM QoS
class queuing and scheduling, performing connection admission control.
IP QoS
queueing
+
scheduling
+
rate limiting
AT M
QoS
ETH
W
ireless
LAN
USB
DSL
Classification
RESOURCE
MANAGEMENT
RESOURCE
MANAGEMENT
IP forwarding
destination
or
label-based
Packect
handeling
INPUT OUTPUT
There are 6 queues defined per ATM interface. So each ATM interface
can have different QoS settings.