3 quality of service – Draytek 2910 User Manual
Page 88
Vigor2910 Series User’s Guide
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Limitation List
Display a list of specific limitations that you set on this web
page.
Start IP
Define the start IP address for limit bandwidth.
End IP
Define the end IP address for limit bandwidth.
TX limit
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.
RX limit
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
Add the specific speed limitation onto the list above.
Edit
Allows you to edit the settings for the selected limitation.
Delete
Remove the selected settings existing on the limitation list.
Index (1-15) in Schedule
Setup
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.
3
3
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6
6
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3
3
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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:
z
Classification: Identifying low-latency or crucial applications and marking them for
high-priority service level enforcement throughout the network.
z
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.