Meru Technical Note - What is the MTU in 'show interfaces Dot11radio ap_id interface_id'
Description
Scope
Solution
The 802.11 MTU (Maximum Transmission Unit) for data frames is 2304 bytes (frame payload size before encryption). The value of 2304 bytes as the maximum length of this field was chosen to allow an application to send 2048-byte pieces of information, which can then be encapsulated by as many as 256 bytes of upper layer protocol headers and trailers.
What is the MTU in "show interfaces Dot11radio ap_id interface_id"
Scope
KB ARTICLE TYPE: Troubleshooting
RELATED SOFTWARE VERSIONS: 4.x, 5.x
KEYWORDS: MTU, Dot11Radio
Solution
The 802.11 MTU (Maximum Transmission Unit) for data frames is 2304 bytes (frame payload size before encryption). The value of 2304 bytes as the maximum length of this field was chosen to allow an application to send 2048-byte pieces of information, which can then be encapsulated by as many as 256 bytes of upper layer protocol headers and trailers.
The IEEE 802.11 header is fairly complex; it is between 24 and 30 bytes (standard Ethernet header is 14 bytes).
Based on the encryption method use, the final payload size varies:
1 WEP adds a header of 8 bytes for a total of 2312 bytes.
2 WPA (TKIP) adds a header of 20 bytes for a total of 2324 bytes.
3 WPA2 (AES) adds a header of 16 bytes, for a total of 2320 bytes
The output of "show interfaces Dot11Radio ap_id interface_id" show MTU as 2346 that is correct and it talks about dot11 MTU.