Download - 802-11-Frame_E_C 3,4 y 6
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802-11-Frame - 1 P. Nicoletti: see note pag. 2
IEEE 802.11 frame format
Pietro Nicolettiwww.studioreti.it
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802-11-Frame - 2 P. Nicoletti: see note pag. 2
Copyright note These slides are protected by copyright and international treaties. The title and the
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802.11 architecture and OSI model
Higher Layer
802.2 Logical Link Control
802.3
CSMA/CD
PHY802.11
IR802.11FHSS
802.11DSSS
802.11a
802.11b
802.11g
802.11h
802.11 Medium Access Control
PHYLayer
DataLink
Layer
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802.11 architecture and OSI model
PMD Sublayer
PLCP SublayerPHY Layer
Management
MAC
Sublayer
MAC Layer
Management
Station
Management
LLC
PHY
MAC
PLCP = Physical layer convergence procedurePMD = Physical medium dipendent
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PLCP: Physical layer convergenceprocedureAdaptation layer between Physical and MAC layers
dependent by speed ad techique transmission
PLCP specific for FHSS PLCP specific for DSSS in 802.11 (1 & 2 Mb/s)
PLCP specific for DSSS in 802.11a (from 6 to 54 Mb/s)
PLCP specific for DSSS in 802.11b (from 1 to 11 Mb/s) PLCP specific for DSSS in 802.11g (from 1 to 54 Mb/s)
Defin:
Operational speed
Modulation and coding
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802.11 frame format
Preamble PLCP header MPDU (MAC PDU)
Bytes: 34 - 2346
Framecontrol
DurationID
Addr 1 Addr 2 Addr 3 Sequencecontrol
Addr 4 Frame Body FCS
Bytes: 2 2 6 6 6 2 6 0 - 2312 4
Protocolversion
Type SubtypeToDS
FromDS
MoreFrag
RetryPwrMgt
MoreData
WEP Rsvd
Bits: 2 2 4 1 1 1 1 1 1 1 1
+
Frame type/MAC service
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Frame Control field Protocol Version:
zero for 802.11 standard
Type= frame type:
data, management, control
Subtype = frame sub-type:
ToDS:When bit is set indicate that destination frame is for DS
FromDS:
When bit is set indicate frame coming from DS
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Frame Control field Retry:
Set in case of retransmission frame
More fragments:
Set when frame is followed by other fragment
Power Management
bit set when station go Power Save mode (PS) More Data:
When set means that AP have more buffered data for astation in Power Save mode
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Frame Control field WEP:
When set indicate that in the Frame Body field there are
datas need to processed by WEP algorithm. Order:
When set indicate restrictions for transmission
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Frame type and MAC service
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Frame type and MAC service
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Frame type and MAC service
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Transmission between stations in the
same BSS
BSS BSS
APAP
Distribution System
Protocolversion
Type SubtypeToDS
FromDS
MoreFrag
RetryPwrMgt
MoreData
WEP Rsvd
Bits: 2 2 4 1 1 1 1 1 1 1 1
0 0
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Frame transmission designated for
Distribution System
Protocolversion
Type SubtypeToDS
FromDS
MoreFrag
RetryPwrMgt
MoreData
WEP Rsvd
Bits: 2 2 4 1 1 1 1 1 1 1 1
1 0
BSS
WDS
BSS
Root
Bridge
Non RootBridge
BSS
Non RootBridge
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Frame transmission coming from
Distribution System
BSS BSS
APAP
Distribution System
Protocolversion
Type SubtypeToDS
FromDS
MoreFrag
RetryPwrMgt
MoreData
WEP Rsvd
Bits: 2 2 4 1 1 1 1 1 1 1 1
0 1
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Transmission designated to STA in other
BSS, transmitted between AP troughWireless Distribution System
Protocolversion
Type SubtypeToDS
FromDS
MoreFrag
RetryPwrMgt
MoreData
WEP Rsvd
Bits: 2 2 4 1 1 1 1 1 1 1 1
1 1
AP
Repeater
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Framecontrol
DurationID
Addr 1 Addr 2 Addr 3 Sequencecontrol
Addr 4 Frame Body FCS
Bytes: 2 2 6 6 6 2 6 0 - 2312 4
Protocolversion
Type SubtypeToDS
FromDS
MoreFrag
RetryPwrMgt
MoreData
WEP Rsvd
Bits: 2 2 4 1 1 1 1 1 1 1 1
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MAC address in 802.11 DA = Destination MAC Address
SA = Source MAC Address
RA = Receiver Address indicate MAC Address of stationin WM that have to receive frame
TA = Transmitter Address indicate station wich have
transmitted frame in WM BSSID
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Framecontrol
DurationID
RA TA FCS
RTS & CTS RTS frame
Duration field contain value in s of time need to transmit
data or management + CTS + ACK + SIFS interval
CTS Frame
Duration field contain value in s obtained by previous
RTS minus time need to transmit CTS and it SIFS interval
Framecontrol
DurationID
RA FCS
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ACK & PS-PollACK frame:
Duration field contain value in s obtained by previous
data or management frame received miuns time need totransmit ACK and it SIFS interval
PS-Poll frame:
AID field contain association ID
Framecontrol
DurationID
RA FCS
Framecontrol
AID BSSID TA FCS
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Beacon frame
Framecontrol
DurationID
Addr 1 Addr 2 Addr 3Sequence
controlAddr 4 Frame Body FCS
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Framecontrol
DurationID
Addr 1 Addr 2 Addr 3Sequence
controlAddr 4 Payload FCS
Bytes: 2 2 6 6 6 2 6 9 - 2320 4
IV ICVData
1 byte
PAD Key ID6 bits 2 bits
Init Vector3 bytes
Bytes: 4 0 - 2312 4
Encripted
MSDU with WEP Extend Payload of 8 bytes
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PLCP Header Contain information for adaptation between PMD e MAC
layers
Header change depending on specific PLCP for: FHSS
PLCP specific for DSSS in 802.11 (1 & 2 Mb/s)
PLCP specific for DSSS in 802.11a (from 6 to 54 Mb/s) PLCP specific for DSSS in 802.11b (from 1 to 11 Mb/s)
PLCP specific for DSSS in 802.11g (from 1 to 54 Mb/s)
Preamble PLCP header MPDU (MAC PDU)