QoS mechanisms on shared data networks have two main objectives:
 

• To prioritize one kind of traffic over

• To guarantee minimal service attributes, such as data rate to certain traffic.

Both of these objectives become relevant in times of network congestion – when network resources are in shortage and there is a need to control and manage the rate between remotes.
 
In order to achieve these QoS objectives, first traffic needs to be classified into predefined classes of service. Then the traffic goes through a series of mechanisms where it is treated according to its class attributes. The most common attributes are:
 

• Committed Information Rate (CIR): This is the guaranteed rate. The sum of all CIRs should not exceed the capacity of the network.

• Extended Information Rate (EIR): This rate will be given only after all CIRs have been supplied and the network has additional resources left.

• Burst Sizes for the above.

Modem QoS
 
The QoS architecture is based on two-level hierarchical queues. The first level defines the bandwidth allocation for each remote. The second level provides eight priority queues per remote, for data based priority.
 
Several Operational modes are supported by the SatExpander QoS function:
 

• Layer 2 Transparent Bridging – Forwarding Mode

• Layer 2 VLAN Switching

• Layer 3 IP Routing Forwarding Modes

• Scheduling

• Surplus

• Shortage