How To Fragment An IE Date: 2013-05-14 Authors: May 2013 Month Year doc.: IEEE 802.11-13/0487r0 May 2013 How To Fragment An IE Date: 2013-05-14 Authors: Dan Harkins, Aruba Networks Dan Harkins, Aruba Networks

Month Year doc.: IEEE 802.11-13/0487r0 May 2013 Abstract A technique to fragment data that is too large to fit in one IE is presented Dan Harkins, Aruba Networks Dan Harkins, Aruba Networks

Month Year doc.: IEEE 802.11-13/0487r0 May 2013 IE Size Limitation Section 8.4.2.1 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 ID Length Information Octets: 1 1 variable Dan Harkins, Aruba Networks Dan Harkins, Aruba Networks

Public Key Definition in P802.11ai D0.5 May 2013 Public Key Definition in P802.11ai D0.5 Element ID Length Key Type 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! FILS Public Key Octets: 1 1 1 variable Dan Harkins, Aruba Networks

Fragmenting Data into Separate IEs May 2013 Fragmenting Data into Separate IEs Use a new Fragment IE Fragmented data is represented by the original IE into which the data would not fit (leading IE) followed by a series of 1 or more Fragment IEs that follow the IE Fragment ID Length Fragmented Data Octets: 1 1 variable Dan Harkins, Aruba Networks

Fragmenting Data into Separate IEs Month Year doc.: IEEE 802.11-13/0487r0 May 2013 Fragmenting Data into Separate IEs For example directly following the PK IE (with length 255) are 2 FR IEs with lengths necessary to fragment the data Reassembly stops when there are no more FR IEs 585 octets PK ID Len KT PK ID 255 FR 255 FR FR 75 KT Dan Harkins, Aruba Networks Dan Harkins, Aruba Networks

Backwards Compatibility May 2013 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 Dan Harkins, Aruba Networks

References 11-13-0478-00-00ai-fragmenting-large-ies May 2013 Month Year doc.: IEEE 802.11-13/0487r0 May 2013 References 11-13-0478-00-00ai-fragmenting-large-ies Dan Harkins, Aruba Networks Dan Harkins, Aruba Networks