11 WLANs requires interoperable, standards-based, evolvable
solutions that extend the features and security capabilities of 802.11 systems and also
support the bandwidth needs of 802.11n High Throughput systems. This section describes
security-related extensions under development at the time this chapter was written.
7.6.1 Security-related changes in the TGn High Throughput Amendment
The security-related changes in High Throughput systems are very limited. Pre-standard
High Throughput systems are being produced and deployed, and those that are WFA
certified require support for AES-CCMP based encryption only. The TKIP algorithm
requires computation of the MIC on the MAC Service Data Unit (MSDU), and encryption
of the MAC Packet Data Unit (MPDU), which is difficult to implement at extremely high
data rates. In addition, the design life-time of TKIP has been passed. Thus support of TKIP
at the High Throughput data rates is not required.
The TGn Draft 2.0 amendment [29] defines MSDU aggregation, that is, construction
of a frame payload with multiple concatenated MSDUs. One bit of the QOS field is used to
indicate the presence of the aggregated MSDU frame when Quality of Service (QoS)
mechanisms are used, and that bit must be included in the CCMP MIC calculation to
guarantee correct interpretation of a received frame.
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