DCF uses carrier sense multiple access / collision avoidance media access, it can be liken to "listen to say." Nodes send data to the channel before the first test is free, and if the channel is idle is ready to send MAC service data unit. If the two STA also detected idle channel and start sending data conflict occurs, this, 802.11 defines a collision avoidance mechanism to reduce the probability of conflict. CSMA way to address the cause of the "hidden node" problem, 802.11 defines a Request to Send / Clear To Send mechanism. STA sending the data frame before sending a short RTS frame, the receiver receives the RTS frame immediately after sending a CTS, RTS and CTS frames contain the next data frame length information. Therefore, the other near STA STA STA and receiving data in the vicinity of the "hidden node" network allocation vector by setting the timer within the specified time in the NAV does not send data to avoid data conflicts. RTS / CTS mechanism and the NAV data frame length can be effectively protected against the "hidden node" of the collision.
When enterprises with Vista? 20% of the universal mission impossible, Microsoft has announced the end of November to prepare for large businesses for sale before the Windows Vista operating system. The problem is that companies are ready to accept Vista? Commissioned by online retailer CDW latest survey showed that 86% of respondents said IT director, affiliated companies plan to deploy Vista, but only 20% of the planned deployment next year. To encourage small businesses to upgrade early to the operating system, Microsoft last week announced an alliance with CompUSA. By mutual agreement, to purchase five or more who want to Vista or Office Small Business 2007 the authorized enterprises, November 30 to under Microsoft Open Value or Open Business license conditions for ordering. However, will not buy boxed software, you must download the. Rosado said that companies encounter compatibility problems, you can use Microsofts Virtual Server and Virtual PC products, virtualization capabilities in Vista, by the internal implementation of Windows XP. He pointed out that the benefits of the implementation of Vista, is the remote management easier, you can just glance at the companys computer monitor and not actually a trip.