ND SatCom SKYWAN IDU 7000, Manual

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128 Network Design and Engineering Guide 2010-10-26
Data Networking
SkyWAN
®
Frame Relay Networking Features
For FR Realtime Dynamic services
-
allocation will happen when the first user packet is received on the PVC. If no user packets
are received for a configured timeout period, the capacity will be automatically released. If
the necessary streaming capacity cannot be allocated due to carrier congestion, the Real-
time PVC will be declared inactive, user traffic will then be discarded at ingress.
Note: If the serial port type is defined as isochronous FRAD, the communication service must
be Realtime. In this case the allocated streaming bandwidth will be derived from the configured
port speed.
4.3.4 SkyWAN
®
FAD Service
In contrast to the generic Frame Relay services, the Sky WAN
®
FAD service allows a mixture
of realtime and non realtime services on a single PVC. This is possible because the Sky WAN
®
IDU can interpret the proprietary network link protocol used to interconnect Sky WAN
®
FADs
over FR PVCs.
This allows the Sky WAN
®
IDU the following functionalities:
- Packets carrying voice traffic will be forwarded via the FR Real Time queue, whereas pack-
ets other than voice traffic will be forwarded over the FR Non Real Time queue even if both
packets are received on the same PVC.
- If a voice call setup is signaled by a FAD, the Sky WAN
®
IDU will automatically request suf-
ficient streaming slot bandwidth for the signaled voice codec. If a call disconnect is signaled
the streaming capacity is automatically released.
In addition to voice traffic, transparent data traffic between FAD serial ports may also be trans-
ported as realtime traffic. In this case the configured serial port speeds on the FAD determines
the allocated streaming bandwidth.
FAD ’Class 7’ traffic
FR data traffic configured as ‘Class 7’ on the FAD serial port will be forwarded into the Sky-
WAN
®
IDU FR real-time queue and thus transferred as FR real-time traffic. SkyWAN band-
width assignment for this data service is optimized for a PDU size of 48 octets (FAD default
value) considering the entire overhead. It is recommended that this default PDU size for 'Class
7' traffic is not changed.
Due to the implemented optimization the required bandwidth for ’Class 7’ traffic has to be cal-
culated by:
- required bandwidth = traffic bandwidth * 1,29.
4.3.5 Traffic Shaping and Congestion Management
Traffic shaping may be enabled on each serial port. If enabled, the received traffic data rate for
each PVC will be measured and compared with traffic policy parameters configured for each
PVC. If more traffic than allowed is received on a PVC, packets may be discarded at ingress
(policy discard). The following traffic policy parameters may be defined on a PVC:
- Committed Information Rate (CIR)