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H323 Message Parse

asked 2020-12-09 16:01:53 +0000

irem gravatar image

updated 2020-12-09 16:07:49 +0000

How Wireshark parses H225 and H 245 messages? I can not find any information in ITU documents. I do not understand tree structure of H225 messages because there is no stable structure, message types are optional.

I would be appreciated if anyone help me. Best Regards.

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answered 2020-12-10 08:22:32 +0000

Anders gravatar image

Hi, I'm not sure I understand, if you look at

  protocolIdentifier             ProtocolIdentifier,
  h245Address                    TransportAddress OPTIONAL,
  sourceAddress                  SEQUENCE OF AliasAddress OPTIONAL,

It's encoded using ASN1 PER encoding rules. If you have a trace try "edit->preferences->protocols-per" Check the box "show internal PER structures". You also need to take a look at:

 Abstract Syntax Notation One (ASN.1) X.680–X.699 specifications 
and particulary:
  ITU-T Rec. X.691 | ISO/IEC 8825-2: Specification of Packed Encoding Rules (PER)
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It was very helpful information for me sir. Thank you very much.

irem gravatar imageirem ( 2020-12-10 09:41:26 +0000 )edit

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Asked: 2020-12-09 16:01:53 +0000

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Last updated: Dec 10 '20