SatX/SE300—
Quality of Service (QoS)
Proprietary and Confidential
136
momentarily increase the allocated interval to the remote thus coping with large data bursts, but may
have an effect on momentary interval allocations of other remotes. A small burst size is intended for
more stable traffic, were the total BW allocation is sensitive over shorter period of time. For optimal
operation, it is recommended to configure the burst size as 10% of the CIR and EIR. The value must be
bigger than the maximum packet size.
The bandwidth management metering is implemented on the forward link, using dual token buckets,
and is done per remote site. The implementation uses a two-rate three-color scheme either color blind
(for MF classification) or color aware (for TOS classification).
11.2.3
Scheduling
The scheduler is based on two level scheduling. The first level of the scheduler collects the packets from
the priority queues of each remote based on the queue priority. The second level of the scheduler
collects the packets from the first level scheduler, based on the CIR, EIR, and available bandwidth. As
the satellite information rate is the limited resource that the scheduler has to control, this resource can
be either in surplus (total data demand is lower than the satellite information rate) or in shortage (total
data demand is higher than the satellite information rate).
11.2.3.1
Surplus
When Satellite information rate is in surplus, the second level scheduler will first allocate to each
remote the CIR bandwidth then, if additional bandwidth is available, it will be distributed as EIR
between the different remotes. The configured CIR+EIR defines maximum payload limit of the remote.
11.2.3.2
Shortage
When satellite information rate is in shortage, the second level scheduler divides the available satellite
information rate between the different remotes, trying to keep the CIR requirements if possible, or
dividing the available satellite information rate in a proportional way to the configured CIR values of the
remotes, keeping a fairness resources utilizations between the different remotes.
F
IGURE
107:
QOS
S
CHEMATIC
Priority1
Priority2
Priority8
Remote1
Priority1
Priority2
Priority8
Remote2
Priority1
Priority2
Priority8
RemoteN
Scheduling by
priority
Scheduling by
Remote