User's Manual
63
February 2007
MP-202 Telephone Adapter
8. Quality of Service (QoS)
Table
8-1: Edit Device Traffic Shaping - Parameter Descriptions
Parameter
Description
Tx Bandwidth
This parameter limits the gateway’s bandwidth
transmission rate. The purpose is to limit the
bandwidth of the WAN device to that of the
weakest outbound link, for instance, the DSL
speed provided by the ISP. This forces the
gateway to be the network bottleneck, where
sophisticated QoS prioritization can be performed.
If the device’s bandwidth is not limited correctly,
the bottleneck will be in an unknown router or
modem on the network path, rendering the
gateway QoS useless.
Rx Bandwidth
In the same manner, this parameter limits the
gateway’s bandwidth reception rate to that of the
DSL modem.
TCP Serialization
You can enable TCP Serialization in its combo
box, either for active voice calls only or for all
traffic. The screen will refresh, adding a ’Maximum
Delay’ field (refer to the figure). This function
allows you to define the maximal allowed
transmission time frame (in milliseconds) of a
single packet. Any packet that requires a longer
time to be transmitted, will be fragmented to
smaller sections. This avoids transmission of
large, bursty packets that may cause delay or jitter
for real-time traffic such as VoIP.
8.1.2 Shaping
Classes
The bandwidth of a device can be divided in order to reserve constant portions of
bandwidth to predefined traffic types. Such a portion is known as a Shaping Class. When
not used by its predefined traffic type, or owner (for example VoIP), the class will be
available to all other traffic. However when needed, the entire class is reserved solely for
its owner. Moreover, you can limit the maximum bandwidth that a class can use even if the
entire bandwidth is available.
When a shaping class is defined for a specific traffic type, two shaping classes are created.
The second class is the 'Default Class', responsible for all the packets that do not match
the defined shaping class, or any other classes that may be defined on the device. This
can be viewed in the Class Statistics screen.