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Reply To: decoding the Setup-UUIE message

Tom Howard

It’s incredibly complicated. Do you really want to do it by hand?

What you have is a Q.931 message with a Protocol Discriminator of 8 and a call reference number of 1122 (hex). 05 means setup. Then there’s the Bearer Capability. The UUIE element starts at position 4C with 7E.

The rest of the message is H.225.0. To decode it, you need to convert it binary, because the line coding is fairly bit orientated.

If you really want to do it, you need to get the H.225.0 ASN.1 spec (you can get it at You need to understand ASN.1 (I think there is a free download of the spec from Then you need to understand the coding which is Packet Aligned Rules (aligned variant). This is defined in X.691 which you can download from You can also download H.225.0 from there.

If this is on an ethernet link, then you can download a free analyser from to decode it for you.