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

2. Month Year
doc.: IEEE /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

3. Month Year
doc.: IEEE /0487r0
May 2013
IE Size Limitation
Section of IEEE Std 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: variable
Dan Harkins, Aruba Networks
Dan Harkins, Aruba Networks

4. 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: variable
Dan Harkins, Aruba Networks

5. 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: variable
Dan Harkins, Aruba Networks

6. Fragmenting Data into Separate IEs
Month Year
doc.: IEEE /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 FR FR FR 75 KT
Dan Harkins, Aruba Networks
Dan Harkins, Aruba Networks

7. Backwards Compatibility
May 2013
Backwards Compatibility
IEEE says in section
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

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