Re: [wirelesslan] Reserved bandwidth by AP

cw wong wrote:
> Case 1:
> A QSTA knows it requires quaranteed downstream bandwidth and it gets
> scheduled TXOP from the QAP through TSPEC negotiation. In this case, the AP
> SME is aware of the bandwidth reservation for the downstream flow.
>
> Case 2:
> Downstream traffic is iniatiated by an application residing in the QAP above the
> wireless MAC. It requires rather constant bandwidth over a long time (streaming 1
> hour video, for example). For some reasons, this downstream flow is not started
> by QSTA, no TSPEC has been exchanged, and thus no bandwidth reservation.
>
> In case 2, is it still possible to protect the traffic? If not protected, it will be
> compromised due to other QoS streams (polled TXOP).

CW,

If the downstream traffic starts before the TSPECs have been agreed
upon, the AP knows about the resources used by the downstream traffic
and how much bandwidth is left. It can reject any TSPEC that
interferes with this already-established flow. This is admission
control and the specifics of how it is done is left to the
implementor.

If the TSPECs have already been established, the AP knows the
resources that have been already allocated. When a new downstream flow
starts, the AP can verify if it has enough resources to support this
traffic. If the flow originates in outside the AP's BSS, something has
to tell the AP about the characteristics of the flow and what kind of
QoS is needed. If the downstream flow needs more resources than the AP
currently has, the AP can reject this flow or it can accept the flow
without guranteeing QoS and try its best. It is in a better position
than the QSTAs since it can pre-empt all BSS traffic by transmitting
after a PIFS.

In short, what the AP does in such a situation is a local policy
decision. Different implementations may take different actions in such
cases.

Hope this helps.

- Harshal

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