6.2.13.8.4 Dynamic Service Change (DSC)

The DSC set of Messages is used to modify the flow parameters associated with a service flow. Specifically, DSC can modify the service flow Specification.

A single DSC Message exchange can modify the parameters of one downlink service flow and/or one uplink service flow.

To prevent packet loss, any required bandwidth change is sequenced between the SS and BS.

The BS controls both uplink and downlink scheduling. The timing of scheduling changes is independent of direction AND whether it’s an increase or decrease in bandwidth. The BS always changes scheduling on receipt of a DSC-REQ (SS-initiated transaction) or DSC-RSP (BS-initiated transaction).

The BS also controls the downlink transmit behavior. The change in downlink transmit behavior is always coincident with the change in downlink scheduling (i.e., BS controls both and changes both simultaneously).

The SS controls the uplink transmit behavior. The timing of SS transmit behavior changes is a function of which device initiated the transaction AND whether the change is an “increase” or “decrease” in bandwidth.

If an uplink service flow’s bandwidth is being reduced, the SS reduces its payload bandwidth first and then the BS reduces the bandwidth scheduled for the service flow. If an uplink service flow’s bandwidth is being increased, the BS increases the bandwidth scheduled for the service flow first and then the SS increases its payload bandwidth.

Any service flow can be deactivated with a DSA command by sending a DSC-REQ Message, referencing the Service Flow Identifier, and including a null ActiveQoSParamSet. However, if a Basic, Primary Management, or Secondary Management Connection of an SS is deactivated that SS is deregistered and shall re-register. Therefore, care should be taken before deactivating such service flows. If a service flow that was provisioned during registration is deactivated, the provisioning information for that service flow shall be maintained until the service flow is reactivated.

An SS shall have only one DSC transaction outstanding per service flow. If it detects a second transaction initiated by the BS, the SS shall abort the transaction it initiated and allow the BS-initiated transaction to complete.

A BS shall have only one DSC transaction outstanding per service flow. If it detects a second transaction initiated by the SS, the BS shall abort the transaction that the SS initiated and allow the BS-initiated transaction to complete.

NOTE—Currently anticipated applications would probably control a service flow through either the SS or BS, and not both. Therefore the case of a DSC being initiated simultaneously by the SS and BS is considered as an exception condition and treated as one.

6.2.13.8.4.1 SS-initiated DSC

An SS that needs to change a service flow definition performs the following operations.

The SS informs the BS using a DSC-REQ. The BS checks the integrity of the message and, if the message is intact, sends a message received (DSX-RVD) response to the SS. The BS shall decide if the referenced service flow can support this modification. The BS shall respond with a DSC-RSP indicating acceptance or rejection. The SS reconfigures the service flow if appropriate, and then shall respond with a DSC-ACK. This process is illustrated in Table 68.

Table 68—SS-initiated DSC

6.2.13.8.4.2 BS-initiated DSC

A BS that needs to change a service flow definition performs the following operations.

The BS shall decide if the referenced service flow can support this modification. If so, the BS informs the SS using a DSC-REQ. The SS checks that it can support the service change, and shall respond using a DSC-RSP indicating acceptance or rejection. The BS reconfigures the service flow if appropriate, and then shall respond with a DSC-ACK. This process is illustrated in Table 69.

Table 69—BS-initiated DSC

6.2.13.8.4.3 DSC state transition diagrams

DSC state transition diagrams are shown in Figure 84–Figure 92.

DSC-Local

Begin

SF Change

Save SF

QoS state

[SS Only]

If decrease uplink bandwidth, modify policing and scheduling parameters

DSC-REQ

Start timer

T7

[SS Only] Start timer T14

Save transmitted

DSC-REQ

Set DSC-REQ Retries available to ‘DSx Request Retries’

DSC-Local

DSC-RSP

Pending

Figure 84—DSC—Locally initiated transaction begin state flow diagram

DSC-Remote

Begin