1) . 802.11 frame payloads (MSDU) can be as high as 2,304 bytes. However, they w

Question

1). 802.11 frame payloads (MSDU) can be as high as 2,304 bytes. However, they will generally be limited to 1500 bytes. This is because _____. a). When transitioning to/from the Ethernet network, Ethernet frame payload is 1500 bytes. b). When passed up to layer 3, packet size can be no larger than 1500 bytes c). Wireless devices are incapable of dealing with a frame larger than 1500 bytes. d). Error rates would be excessive if the frame size exceeded 1500 bytes. 2). It is possible that a particular client can hear transmissions from an AP, and that AP can hear transmissions from that client, but that client cannot hear transmissions from another client. To aid in collision avoidance, which of the following mechanisms are used? a). RTS/CTS b). Active mode c). ACK d). Passive scanning 3). An 802.11g AP configured to operate in mixed mode allows for which of the following? Choose 2. a). DSSS & OFDM transmissions b). DSSS transmissions only c). OFDM transmissions only d). Communications with both 802.11b and 802.11g devices e). Communications with both 802.11g and 802.11ac devices 4). In an ESS, the decision to roam is made by the client station. Which AP to associate with is usually based on three factors. List these 3 factors and briefly describe why the client would take these factors into account on which AP to associate with. 5). In network 192.168.1.0 /24, the layer 3 broadcast address is 192.168.1.255. What is the broadcast address at layer 2?

Explanation / Answer

1) A

I quote from the IEEE 802.11 Handbook 2nd edition page 40. " The value of 2304 bytes as the maximum length of this field was chosen to allow an application to send 2048 byte of information, which can then be encapsulated by as many as 256 bytes of upper layer protocol headers and trailers.

The max IEEE 802.11 MSDU size is 2304 octets. This is the number to remember. Its is the maximum size of the frame body before encryption.

The popular IP MTU of 1500 octets is a sequence of Ethernet limits. A client server application usinf Wi-Fi only might use an MTU higher than 1500. I have observed this Apple iTunes application.

2) A

RTS/CTS(Request to send/ Clear to send) is the optional mechanism used by the 802.11. These are used in wireless networking protocol to reduce Frame collisions introduced by the hidden node problem.

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