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snmp.time respective to retransmits

asked 2023-04-24 14:48:44 +0000

nfldson gravatar image

updated 2023-04-24 14:53:44 +0000

My operational case is when capturing SNMP packets and if the server detects no/slow response (TO) it will retransmits the same request ID, application will ignore TO response and keep trying (max3) until a response within TO is received

Wireshark when displaying snmp.time associates all the delayed responses to the last transmitted SNMP get request associated to the request ID

  1. packet 1 , id1 request get @ time 0 , snmp.time = - 30 seconds
  2. packet 2 , id1 request get @ time +10 seconds , snmp.time = - 20 seconds
  3. packet 3 , id1 request get @ time +20 seconds , snmp.time = ( no snmp.time as it is a get request )
  4. packet 4 , id1 response @ time + 25 seconds , snmp.time = 5 seconds
  5. packet 5 , id1 response @ time + 30 seconds , snmp.time = 10 seconds
  6. packet 6 , id1 response @ time + 35 seconds , snmp.time = 15 seconds

    I want (expect) packets 4-6 to have snmp.time (25,30,35)

Wireshark provide snmp.time to repeats get requests relative the last get request Wireshark provide snmp.time for responses (multiple) to last snmp get request

Is there a way to configure to display differently?

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answered 2023-04-24 16:55:36 +0000

Chuckc gravatar image

rfc3416: Version 2 of the Protocol Operations for the Simple Network Management Protocol (SNMP)

However, in order to calculate the round trip time for transmission and processing of a request-response transaction, the application needs to use a different request-id value on a retransmitted request. The latter strategy is recommended for use in the majority of situations.

With a non-unique request ID in all requests and responses, how do you know the responses are not arriving out of order?

The value of the request-id field in a Response-PDU takes the value of the request-id field in the request PDU to which it is a response. By use of the request-id value, an application can distinguish the (potentially multiple) outstanding requests, and thereby correlate incoming responses with outstanding requests. In cases where an unreliable datagram service is used, the request-id also provides a simple means of identifying messages duplicated by the network. Use of the same request-id on a retransmission of a request allows the response to either the original transmission or the retransmission to satisfy the request.

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There would be no guarantee , application is tracking responses. Also if packet(s) were lost , would result in some RT not being able to be calculated. In this case response is delayed to server and can not track specific RT in csv export.

nfldson gravatar imagenfldson ( 2023-04-25 22:36:31 +0000 )edit

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Asked: 2023-04-24 14:48:44 +0000

Seen: 386 times

Last updated: Apr 24 '23