MP-20x Telephone Adapter 72 Document #: LTRT-50609
User's Manual
2. From the 'WAN Devices Bandwidth (Rx/Tx)' drop-down list, select the Rx and Tx
bandwidth limitation for the device.
3. In the 'QoS Profiles' group, select a profile.
4. Click OK.
Note: Selecting a new QoS profile deletes all previous QoS settings.
8.2 Traffic Shaping
Traffic Shaping is the solution for managing and avoiding congestion where a high speed
LAN meets limited broadband bandwidth. A user may have, for example, a 100 Mbps
Ethernet LAN with a 100 Mbps WAN interface router. The router may communicate with
the ISP using a modem with a bandwidth of 2 Mbps. This typical configuration makes the
modem, having no QoS module, the bottleneck. The router sends traffic as fast as it is
received, while its well-designed QoS algorithms are left unused. Traffic shaping limits the
bandwidth of the router, artificially forcing the router to be the bottleneck.
A traffic shaper is essentially a regulated queue that accepts uneven and/or bursty flows of
packets and transmits them in a steady, predictable stream so that the network is not
overwhelmed with traffic.
While Traffic Priority allows basic prioritization of packets, Traffic Shaping provides more
sophisticated definitions such as:
Bandwidth limit for each device
Bandwidth limit for classes of rules
Prioritization policy
TCP serialization on a device
In addition, you can define QoS traffic shaping rules for a default device. These rules are
used on a device that has no definitions of its own. This enables the definition of QoS rules
on Default WAN, for example, and their maintenance even if the PPP or bridge device over
the WAN is removed.
MP-20x also supports dynamic traffic shaping during a call. Traffic shaping is critical in
residential VoIP gateways because of the bottleneck created in the ADSL or Cable modem,
mainly in the upload direction. Dynamic traffic shaping ensures a minimum bandwidth for
VoIP calls. Without dynamic traffic shaping, traffic shaping limits the bandwidth at all times,
even if the user is not making a VoIP call and therefore, the service provider needs to
configure the QoS traffic shaping transmit (Tx) bandwidth according to the user's specific
upload bandwidth. Configuring a lower value results in a lower upload bandwidth (not only
during VoIP calls).
Dynamic traffic shaping enables the service provider to configure two upload traffic shaping
bandwidth parameters:
"Tx Bandwidth" - for all traffic
"Tx Bandwidth during Call" - for VoIP calls
MP-20x normally uses the "Tx Bandwidth" value. When the user makes a VoIP call (i.e.
any phone/s connected to MP-20x is ringing or off-hook), MP-20x switches to use the "Tx
Bandwidth during Call" value.
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