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WLAN Analyzer and Decoder - CommView for WiFi

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Introduction
About CommView for WiFi
What's New
Using the Program
Driver Installation
Overview
Main Menu
Nodes
AP and Station Details Window
Channels
Latest IP Connections
Packets
Logging
Viewing Logs
Rules
Advanced Rules
Alarms
WEP/WPA Keys
Reconstructing TCP Sessions
Reconstructing UDP Streams
Searching Packets
Statistics and Reports
Using Aliases
Packet Generator
Visual Packet Builder
NIC Vendor Identifier
Scheduler
Node Reassociation
Using Remote Agent for WiFi
Using RPCAP
Using Aruba Remote Capture
Port Reference
Setting Options
Frequently Asked Questions
VoIP Analysis
Introduction
Working with VoIP Analyzer
SIP and H.323 Sessions
RTP Streams
Registrations, Endpoints, and Errors
Call Logging and Reports
Call Playback
Viewing VoIP Logs
Working with Lists in VoIP Analyzer
NVF Files
Advanced Topics
Monitoring 802.11n and 802.11ac Networks
Understanding CRC and ICV Errors
Understanding WPA Decryption
Understanding Signal Strength
Capturing A-MPDU and A-MSDU Packets
Using CommView for WiFi in a Virtual Machine
Multi-Channel Capturing
Spectrum Analysis
Capturing High Volume Traffic
Running CommView for WiFi in Invisible Mode
Command Line Parameters
Exchanging Data with Your Application
Custom Decoding
CommView Log Files Format
Information
How to Purchase CommView for WiFi

Capturing A-MPDU and A-MSDU Packets

The 802.11n and 802.11ac 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 the 802.11n and 802.11ac standards. A-MPDU is widely used in 802.11n and 802.11ac devices. A-MPDUs can be captured by any 802.11n or 802.11ac 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. Support for A-MSDUs is optional in the 802.11n standard. A-MSDUs are rarely used in 802.11n devices. A-MSDUs can be captured by the following adapters that are supported by CommView for WiFi:

· Any recommended 802.11n PC Card, ExpressCard, PCI, or PCIe adapters based on Atheros chipsets and 802.11n USB adapters based on Ralink chipsets. A-MSDUs of up to 3,839 bytes are supported.
· Any recommended 802.11n USB adapters based on Atheros chipsets and CACE Technologies AirPcap adapters. A-MSDUs of up to 7,935 bytes are supported.
· Any recommended 802.11ac USB adapters based on Realtek chipsets. A-MSDUs of up to 7,935 bytes are supported.

Note that large frames, such as A-MSDUs, are frequently damaged, especially when being sent at high data rates.