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The 802.11n, 802.11ac, and 802.11ax standards allow sending
multiple frames per single access to the medium by combining the
frames together into one larger frame. There are two forms of frame
aggregation: Aggregated Mac Protocol Data Unit (A-MPDU) and
Aggregated Mac Service Data Unit (A-MSDU). CommView for WiFi can
capture both types of aggregated packets, as explained
below.
Received A-MPDU frames are split into individual packets at the
hardware level. A-MPDUs can be up to 64 Kbytes in size. When an
A-MPDU is captured, it is passed to the application level as a
number of disaggregated packets that look like any other packets.
These packets are not marked by CommView for WiFi in any special
manner. Support for A-MPDUs is mandatory in modern Wi-Fi standards
and it is widely used. A-MPDUs can be captured by any adapter that
is supported by CommView for WiFi.
Received A-MSDU frames are split into individual packets at the
software level. A-MSDUs can be up to 7,935 bytes in size. When an
A-MSDU is captured, it is passed to the application level as a
single, aggregated packet—i.e., in the form in which it was
originally received. If the aggregated packet is not damaged and if
it can be decrypted (if decryption is necessary), CommView for WiFi
will disaggregate the A-MSDU and will display the individual
packets on the packet list. Such packets will be marked as
"Subframe #... of A-MSDU #..." in the "More details" column.
Additionally, the subframes will be followed by the original
aggregated A-MSDU, which will be marked as "A-MSDU #...." If the
aggregated packet is damaged or encrypted, only the original A-MSDU
will be displayed. A-MSDUs can be captured by any recommended
802.11ac and 802.11ax adapters.
Note that large frames, such as A-MSDUs, are frequently damaged,
especially when being sent at high data rates.
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