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Submission doc.: IEEE 11-13/0487r0 May 2013 Dan Harkins, Aruba NetworksSlide 1 How To Fragment An IE Date: 2013-05-07 Authors:
Submission doc.: IEEE 11-13/0487r0 May 2013 Dan Harkins, Aruba NetworksSlide 2 Abstract A technique to fragment data that is too large to fit in one IE is presented
Submission doc.: IEEE 11-13/0487r0May 2013 Dan Harkins, Aruba NetworksSlide 3 IE Size Limitation Section 18.104.22.168 of IEEE Std 802.11-2012 gives base format for an IE: The Length field defines the length of the Information field One octet Length means Information cannot be greater than 255 octets! Some IEs have fixed components after the Length that further reduce the size of the Information field Element IDLengthInformation Octets: 1 1 variable
Submission doc.: IEEE 11-13/0487r0 Public Key Definition in P802.11ai D0.5 With a Key Type component (indicates certificate or 2 kinds of raw public key), the public key is limited to 254 octets! This may be acceptable for certain raw ECC public keys Too small for acceptable FFC public keys Too small for certificates (even those with ECC public keys) Need some way to convey data > 255 octets using IEs that limit data to 255 octets! Slide 4Dan Harkins, Aruba Networks May 2013 Element IDLengthKey Type Octets: 1 1 1 variable FILS Public Key
Submission doc.: IEEE 11-13/0487r0 Fragmenting Data into Separate IEs Use a new Fragment IE IEs that can be fragmented are defined such that: A length greater than the size of the fixed components means the data is not fragmented A length that indicates the length of the fixed components means that the data is fragmented Fragmented data is represented by 1 or more Fragment IEs that follow the IE that is fragmented Slide 5Dan Harkins, Aruba Networks May 2013 Fragment IDLengthFragmented Data Octets: 1 1 variable
Submission doc.: IEEE 11-13/0487r0May 2013 Dan Harkins, Aruba NetworksSlide 6 Fragmenting Data into Separate IEs Directly following the PK IE (with length 1) are 3 FR IEs with lengths necessary to fragment the data Upon receipt the PK IE of length 1 indicates fragmentation Reassembly stops when there are no more FR IEs PK ??? KT 585 octets PK 1 KT FR 255 FR 255 FR 75
Submission doc.: IEEE 11-13/0487r0 Backwards Compatibility IEEE 802.11-2012 says in section 22.214.171.124 IEs have a fixed order in a frame IEs that are not understood are skipped over Implications of IE ordering Cannot rearrange order of existing IEs New IEs can be defined to go in any order without affecting existing implementations New IEs that can be fragmented are defined as such with a fixed order Fragment IE is special It uses the same order of the IE that is being fragmented It will be skipped over by existing implementations along with IE it is fragmenting Slide 7Dan Harkins, Aruba Networks May 2013
Submission doc.: IEEE 11-13/0487r0May 2013 Dan Harkins, Aruba NetworksSlide 8 References 11-13-0478-00-00ai-fragmenting-large-ies
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