May 2013 doc IEEE 11 130487 r 0

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May 2013 doc. : IEEE 11 -13/0487 r 0 How To Fragment An IE

May 2013 doc. : IEEE 11 -13/0487 r 0 How To Fragment An IE Date: 2013 -05 -07 Authors: Submission Slide 1 Dan Harkins, Aruba Networks

May 2013 doc. : IEEE 11 -13/0487 r 0 Abstract A technique to fragment

May 2013 doc. : IEEE 11 -13/0487 r 0 Abstract A technique to fragment data that is too large to fit in one IE is presented Submission Slide 2 Dan Harkins, Aruba Networks

May 2013 doc. : IEEE 11 -13/0487 r 0 IE Size Limitation • Section

May 2013 doc. : IEEE 11 -13/0487 r 0 IE Size Limitation • Section 8. 4. 2. 1 of IEEE Std 802. 11 -2012 gives base format for an IE: Octets: Element ID Length Information 1 1 variable • 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 Submission Slide 3 Dan Harkins, Aruba Networks

May 2013 doc. : IEEE 11 -13/0487 r 0 Public Key Definition in P

May 2013 doc. : IEEE 11 -13/0487 r 0 Public Key Definition in P 802. 11 ai D 0. 5 Element ID Octets: 1 Length 1 Key Type FILS Public Key 1 variable • 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! Submission Slide 4 Dan Harkins, Aruba Networks

May 2013 doc. : IEEE 11 -13/0487 r 0 Fragmenting Data into Separate IEs

May 2013 doc. : IEEE 11 -13/0487 r 0 Fragmenting Data into Separate IEs • Use a new Fragment IE Octets: Fragment ID Length Fragmented Data 1 1 variable • 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 Submission Slide 5 Dan Harkins, Aruba Networks

May 2013 doc. : IEEE 11 -13/0487 r 0 Fragmenting Data into Separate IEs

May 2013 doc. : IEEE 11 -13/0487 r 0 Fragmenting Data into Separate IEs 585 octets PK PK 1 ? ? ? KT KT FR 255 FR 75 • 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 Submission Slide 6 Dan Harkins, Aruba Networks

May 2013 doc. : IEEE 11 -13/0487 r 0 Backwards Compatibility • IEEE 802.

May 2013 doc. : IEEE 11 -13/0487 r 0 Backwards Compatibility • IEEE 802. 11 -2012 says in section 8. 3. 3. 1 • 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 Submission Slide 7 Dan Harkins, Aruba Networks

May 2013 doc. : IEEE 11 -13/0487 r 0 References 11 -13 -0478 -00

May 2013 doc. : IEEE 11 -13/0487 r 0 References 11 -13 -0478 -00 -00 ai-fragmenting-large-ies Submission Slide 8 Dan Harkins, Aruba Networks