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 ------------------------ Yahoo! Groups Sponsor --------------------~--> Get Bzzzy! (real tools to help you find a job). Welcome to the Sweet Life. http://us.click.yahoo.com/KIlPFB/vlQLAA/TtwFAA/5AhqlB/TM --------------------------------------------------------------------~-> http://www.wireless--lan.com/ http://www.wlanforum.com/ http://groups.yahoo.com/group/wirelesslan/ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/wirelesslan/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
