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Deploying QoS (Quality of Service) management to guarantee that all applications receive the
service levels required and sufficient bandwidth to meet performance expectations is indeed
one important aspect of modern enterprise network.
One reason for QoS is that numerous TCP-based applications tend to continually increase their
transmission rate and consume all available bandwidth, which is called TCP slow start. If
other applications are not protected by QoS, it will detract much from their performance in the
overcrowded network. This is especially essential to those are low tolerant of loss, delay or
jitter (delay variation).
Another reason is due to congestions at network intersections where speeds of interconnected
circuits mismatch or traffic aggregates, packets will queue up and traffic can be throttled back
to a lower speed. If there's no defined priority to specify which packets should be discarded
(or in another term "dropped") from an overflowing queue, packets of sensitive applications
mentioned above might be the ones to drop off. How this will affect application performance?
There are two components within Primary configuration of QoS deployment:
Classification: Identifying low-latency or crucial applications and marking them for
high-priority service level enforcement throughout the network.
Scheduling: Based on classification of service level to assign packets to queues and
associated service types
The basic QoS implementation in Vigor routers is to classify and schedule packets based on
the service type information in the IP header. For instance, to ensure the connection with the
headquarter, a teleworker may enforce an index of QoS Control to reserve bandwidth for
HTTPS connection while using lots of application at the same time.
One more larger-scale implementation of QoS network is to apply DSCP (Differentiated
Service Code Point) and IP Precedence disciplines at Layer 3. Compared with legacy IP
Precedence that uses Type of Service (ToS) field in the IP header to define 8 service classes,
DSCP is a successor creating 64 classes possible with backward IP Precedence compatibility.
In a QoS-enabled network, or Differentiated Service (DiffServ or DS) framework, a DS
domain owner should sign a Service License Agreement (SLA) with other DS domain owners
to define the service level provided toward traffic from different domains. Then each DS node
in these domains will perform the priority treatment. This is called per-hop-behavior (PHB).
The definition of PHB includes Expedited Forwarding (EF), Assured Forwarding (AF), and
Vigor3100 Series User's Guide
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Define the limitation for the speed of the upstream. If you do
not set the limit in this field, the system will use the default
speed for the specific limitation you set for each index.
Define the limitation for the speed of the downstream. If you do
not set the limit in this field, the system will use the default
speed for the specific limitation you set for each index.
Add the specific speed limitation onto the list above.
Allows you to edit the settings for the selected limitation.
Remove the selected settings existing on the limitation list.
You can type in four sets of time schedule for your request.
All the schedules can be set previously in Application –
Schedule web page and you can use the number that you have
set in that web page.
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