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How to determine the message length or size of a diameter message?

+4 votes
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From Wireshark Packet capture how the Diameter "Length' field calculation value arrive for the diameter message size.
My query is :
1. Does it take into account all the AVPs used in the Diameter Request/Response Message.

posted Feb 1, 2016 by Chinmoy Padhi

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1 Answer

+1 vote

Attached is the diameter header followed by AVPs, Message Length is 24 bit field which contains the Size of the Diameter message including the header fields. (I hope I understood the problem correctly)

Diameter Header

answer Feb 1, 2016 by Salil Agrawal
Thanks Salil, I want to determine the size of CCRequest message. So if we see the CCR message in capture it won't be 24 bits, may be more than that. So I want to know how it arrive at that value.I tried to add all the AVPs in CCRequest message and didn't get the exact message size for that request message. Let say you have Diameter header Length whose value is 500 bytes and sum of All AVPs in the CCRequest message comes to 480. I am not sure my understanding is correct or not.May be if you look into a capture you will surely come up with correct idea.
Thanks
Chinmoy
commented Feb 1, 2016 by Chinmoy Padhi
Your understanding is correct header size is 20 bytes so if message length is 500 then all AVP would be 480 bytes (500-20).
commented Feb 1, 2016 by Salil Agrawal
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I have a couple of questions about maximum message size in Diameter.

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