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decoding the Setup-UUIE message

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  • #21568 Reply
    lmak
    Guest

    I am trying to use Q.931/H.225.0 (ASN.1) to decode the following “setup” message. I could not go very far.
    Can some one point me to a better document that has the codes for the rest of the message attributes (e.g. h323-message-body choice, h245Address, sourceAddress, ..etc).

    Thanks.
    Leo

    —————hex dump———–
    00000030 08 02 11 22 05 04 03 88 C0 A5 …”……
    00000040 28 0A 64 64 20 6D 61 63 63 6F 6D 00 7E 00 BD 05 (.dd.maccom.~…
    00000050 10 A8 06 00 08 91 4A 00 02 01 40 08 00 64 00 64 ……J…@..d.d
    00000060 00 20 00 6D 00 61 00 63 00 63 00 6F 00 6D 22 C0 …m.a.c.c.o.m”.
    00000070 B5 00 53 4C 16 4D 69 63 72 6F 73 6F 66 74 AE 20 ..SL.Microsoft..
    00000080 4E 65 74 4D 65 65 74 69 6E 67 AE 00 03 33 2E 30 NetMeeting…3.0
    00000090 00 00 C0 A8 01 7C 06 B8 00 AF D0 98 42 4D 91 E4 …..|……BM..
    000000A0 40 B0 6E 97 F0 D6 56 27 32 00 45 0C 07 00 C0 A8 @.n…V’2.E…..
    000000B0 01 70 07 9C 11 00 C6 01 5C 4F 9A 27 EA 4B 9F 09 .p……\O.’.K..
    000000C0 10 57 2E 0F 26 28 01 00 01 00 40 B5 00 53 4C 3C .W..&(….@..SL

    #21569 Reply
    Tom Howard
    Guest

    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 http://www.packetizer.com). You need to understand ASN.1 (I think there is a free download of the spec from http://www.itu.int). 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 http://www.itu.int. You can also download H.225.0 from there.

    If this is on an ethernet link, then you can download a free analyser from http://www.voice2sniff.org to decode it for you.

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Reply To: decoding the Setup-UUIE message
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