the capture layer about tcpdump

[叶铮 <yezheng62155 () huawei com>]

 <mailto:germylure () huawei com> Hello ,everyone, I need your help! 
 
      I am a freshman on tcpdump, I have a problem about it, I try to
capture the Trafic Control Frame(2nd layer ,the Pause Frame,which used to
tell the Switch pause Transmitting frames to the host, because the host RX
buffer is near full).
      The Pause Frame ethertype is 0x8808 , but I have never capture one
Pause packet successfully, why ? I want to know which layer the tcpdump
works ? ethernet ,IP or TCP/UDP ?  thank you 
 
   
     additional info : NIC chip info
      
     The minimum size frame is 512 bits or 64 bytes (see Figure 122). MAC
control frames must pad zeros into the unused portion
of the payload. A flow control frame contains the following fields:
*    Destination address field, set to 01-80-C2-00-00-01
*    Source address field set to unique MAC address of sender
*    LL/Type field set to the 802_3_MAC_CONTROL value, set to 88-08
*    MAC control pause opcode (00-01), pause_time, and reserved field
(zeros)
 
      
   thanks !
Alex   
 

叶铮
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