ND SatCom SKYWAN IDU 1070, Руководство пользователя

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2010-10-26 Network Design and Engineering Guide 41
General Carrier Design
Network Traffic Estimation
2.4 Network Traffic Estimation
The starting point for a satellite network configuration is an evaluation of customer require-
ments. The mayor points to be specified here are:
-
The quantity of locations to serve,
- Network topology (e.g. meshed, hybrid or star),
- Traffic profiles and patterns,
- Traffic types and user application requirements.
For larger networks it is typically not possible to perform an explicit estimation for each individ-
ual station. Generally it is sufficient to classify stations according to their typical traffic quantity
and profile and define only a few station types (e.g. Headquarters, regional hubs, remote sites).
The assumption here is that all stations belonging to a specific station type have the same traf-
fic profile.
The following results should be derived from the traffic estimation:
-
The required network topology and connectivity.
- The total user traffic capacity required in the network.
- For Sky WAN
®
networks with multiple carriers: The required user traffic capacity for each
Sky WAN
®
carrier.
Traffic Profiles
The traffic profile of a station typically consists of the following traffic types:
- Non real-time (NRT) data traffic (IP or Frame Relay),
- Real-time (RT) data traffic (IP or Frame Relay),
- Voice traffic (served by analog or digital Sky WAN
®
FAD interfaces or VoIP systems).
For the purpose of traffic estimation it makes no difference if the traffic is based on the IP or
Frame Relay functionality. Estimations for non real-time and real-time traffic however, have to
be done in a different way.
Non real-time traffic , for example file downloads, are “flexible” concerning their bandwidth re-
quirement. They work if the available bandwidth is low or high, just the download time will vary
according to the available network capacity. For the traffic estimation only a minimum or “com-
mitted” data rate has to be specified for this type of applications. In reality in
Sky WAN
®
net-
works more bandwidth might be available because of the flexible bandwidth allocation allowing
to assign currently unused capacity in the network to any station.
Real-time data traffic , for example real-time audio and video streaming, are by nature appli-
cations which require a constant data rate. If this rate is not available, the service will suffer
from severe quality degradation or might not work at all. Therefore, the traffic estimation is
based on the data rate given by the specific application.
i
For all scenarios this reduced flexibility only applies to real-time bandwidth served
by streaming slots. For non real-time services the master can allocate any unused
slot to any requesting station even if this slot is located within the private bandwidth
pool of another station.