QUESTION: 261

Which of the following features assist in the reduction of lost data due to wireless LAN PC Cards (Clients) entering sleep mode while operating in AD HOC mode? Select two.

Access point queue buffers
The access point transmits the TIM to notify stations of queued packets
PC Cards have an established wake up period
Use of ATIM window

Answer(s): C,D

Explanation:

Announcement Traffic Information Message (ATIM) - used in Ad Hoc mode to
indicate to stations the presence of transmissions bound for a particular station; tells stations not to enter sleep mode before receiving their transmitted frames An ATIM is used for the purpose of notifying stations that are using power save poll (PSP) mode that there is data queued for them by other stations, awaiting delivery. After stations send the ATIMs to other stations, the ATIM window (the time during which ATIMs are sent) closes and the data is then delivered according to CSMA/CA medium access rules.
Incorrect answers:
In ad-hoc mode there is no AP and this fact eliminates A and B as answers See page 358 CWNA Study Guide 3rd edition

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