Wireshark-users: Re: [Wireshark-users] Filtering options to remove redundant frames in IEC 61850
Hello to all!

First a little introduction of myself. I am working with Schneider Electric in IEC 61850 based substation automation solutions - R&D division. 
I am testing GOOSE messaging "ping - pong " between a real device and a Test Set. The way GOOSE works is this :


If any data value (encapsulated in the GOOSE frame changes) lots of GOOSE messages are transmitted with the changed values using multicast mode. Since the mode is "best effort" and the device will not know if the recipient has received the message (unlike connection oriented TCP) , the device keep on re-sending the frames continuously with a pre-set re-transmission time until another data value change take place. In GOOSE implementation, the field "StNum" in GOOSE PDU gets incremented every time there is an update in the data value. There is also a field of "SeqNum" in the GOOSE PDU which keeps on incrementing as long as there is no change in the data value. 

e.g A GOOSE message with first change in data value will send GOOSE frame with StNum = 1 and SeqNum = 0,1,2,3,4, .... unless there is another change in the data value. If a data value changes the GOOSE exchange will contain StNum = 2 and SeqNum = 0,1,2,3,4, ... and so on ... 


I am triggering 1000 such data value changes with every data value changing in 1sec.  What I want finally is a file with GOOSE frames with unique "StNum" field. That is my file should contain only 1000 frames with 100 unique "StNum" values only. Is there a way to use filtering capabilities to achieve such objective. ? 

thanks in advance