1) Asynchronous data service
2) Security services
3) Media access controlWith asynchronous data service…
Peer LLC’s exchange MSDU’sWith security services, there are 3 options:
Authentication, WEP or 802.11iEvery frame contains 3 things:
1) MAC header
2) Variable length frame body
3) FCSThe frame body is specific to…
1 of the 3 frame types in 802.11How long are CRC’s?
4 bytesThe 3 802.11 frame types are:
1) Data
2) Control
3) ManagementWhat do control frames do in 802.11?
Send CTS/RTS, ACK etc.What do management frames do in 802.11?
Send associations and beaconsManagement frames are ______________ to upper layer protocols
Not forwarded802.11 is a CSMA/CA network, meaning it uses physical and virtual carrier sense mechanismsVirtual carrier sense mechanisms….
Announce the use of media (NAV)NAV stands for:
Network allocation vectorThe distributed coordination function simply means the exchange of…
RTS’s and CTS’sBoth RTS’s and CTS’s contain a…
Duration fieldThe duration field is…
The time to tx data frame, ack frame, and inter fame spacesFour diff. types of IFS’s:
1) SIFS: short inter frame space
2) PIFS: point coordination function inter frame space
3) DIFS: distributed coordination function inter frame space
4) EIFS: extended inter frame spaceWhat does PCF do?
Creates contention free access to wireless network for tx devices, only available in infrastructure networks because AP is the polling master and central point of this optional method of accessThe MAC layer can intentially _________ MSDU’s
reorderWhen the MAC layer is reordering MSDU’s, what type of frames get priority?
unicastThe frame control field in the MAC header is how long
2 bytesThe protocol version field would be what for the current version?
00The type bits would be set to what for each type of MAC frame
1) 00 – mgmt
2) 01- ctrl
3) 10 – dataThe subtype field in the frame control field consists of…
Additional info about whatever frame type has been specified in the type sectionThe last half of the frame control field is…
1 byte of flagsIf the destination is the distribution system, the To DS bit would be set to…
1If the source is the distribution system, the From DS bit would be set to…
1If a wireless distribution system is in play, the From and To DS bits are set to
1If an ad-hoc network is in play, the From and To DS bits are set to
0If the More flag is set to 1, what does this mean?
It means the MPDU is too largeWhat does 802.11 do with MPDU’s which are too large
It can fragment them like TCP doesIf the retry flag is set to 1…
The frame has been transmitted beforeIf the power management flag is set to 1, the station is in
Power save modeIf the more data flag is set to 1….
The station is telling the receiver that the transmission is not complete and it should not enter power save modeIf the protected frame flag is set to 1…
The body is encryptedIf the order flag is set to 1…
An upper layer protocol requested strict order transmission, meaning the MAC layer will not reorder anythingThe duration field has 2 functions:
1) Remaining duration
2) AID (association ID)In the duration field, if bit 15 is 0 the field is…
The remaining durationIn the duration field, if bit 15 is 1 the field is…
The AID of the txing stationThere are ___ address fields in an 802.11 frame
4Data frames use how many address fields in an 802.11 frame?
3 or 4Control and management frames can use as little as 1 address field in an 802.11 frameThe first 3 bytes of a MAC addr =
The OID of the vendorThe last 3 bytes of a MAC addr =
The unique ID of the MAC entity5 types of addr’s in 802.11:
1) BSSID (ID’s boundaries)
2) Src
3) Dst (final dst)
4) Tx addr (last to tx)
5) Rx addr (next to rx)The sequence control field has 2 subfields which are:
1) Fragment # (4 bits)
2) Frame seq # (12 bits)The max frame body size for unencrypted frames is…
2304 bytesThe max frame body size for encrypted frames is…
2346 bytes
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