EASTAR UHP-1000 SERIES SATELLITE ROUTER
INSTALLATION AND OPERATION MANUAL, V. 2.3
(SW VERSION 2.2.9)
© ROMANTIS 2010
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www.romantis.com
Figure 20 Principle of operation of Traffic Shaper
Examples of TS operation:
Two streams share a 800 Kbit/s channel. CIR of the green stream is 200 Kbit/s, that of the
red one – 400 Kbit/s. Maximum stream bit rates are not limited. The blue line stands for
general load of the channel. Dashed line means the desired stream bit rates.
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Figure 21 Example of Traffic Shaper operation
By points (Figure 21):
Green traffic begins entering at 300 Kbit/s. This is within CIR limits and hence TS
does not delay packets.
Incoming green traffic bandwidth increases three-fold – up to 600K. Traffic begins to
be delayed since the stream bandwidth is insufficient. As the load of the general
channel is low, TS begins to smoothly expand green stream bandwidth until its
overload is eliminated. Stream rate of increase is proportional to the ‖Slope Factor‖
which is set in the TS configuration.
Green stream bandwidth is stabilized at 600K to pass the traffic without delay.
Red traffic starts with 700K bandwidth. Gets immediately 400K (CIR). The channel
gets overloaded. TS almost immediately narrows the green stream bandwidth up to
CIR=400К to remove modulator overload. Since both streams are overloaded and
want to get a wider bandwidth, a fair (proportional to their CIR) distribution of the
bandwidth between them is initiated.
The bandwidth is divided in proportion of 33% to the red stream (CIR=400K) and
66% to the green stream (CIR=200K). Channel load is close to 100%.
Green traffic reduces to 250K. Nothing happens since its bandwidth is still wider than
CIR.
Green traffic ceases. Modulator load drops and TS starts to expand overloaded red
stream.
Red stream gets stabilized at 700K to transmit traffic without delay.
In this example adaptation of IP-protocols to the delay is not taken account of,
otherwise the example would be too complicated but the algorithm is designed for this
adaptation.
TS does not track the situation when the sum of assigned CIRs exceeds the modulator
bit rate. In this case TS cannot guarantee CIR streams – this is just impossible, but
anyway it will try to provide maximum fair distribution of the bandwidth.
TS adjustment commands:
