anchor.diff:  
   The version of the ICMP protocol.
   
  +==== icmp.request.message
  +
  +type: string
  +
  +A human readable form of the request.
  +
   ==== icmp.request.type
   
   type: int
  
positive.code: type: int
  
  The request code.
  
  ==== icmp.response.type
  
  
negative.code: 
  
  [[exported-fields-icmp]]
  === ICMP Fields
  
  ICMP specific event fields.
  
  