OPC UA PubSub Sniffing concepts: Difference between revisions

From OPC Labs Knowledge Base
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= Special cases =
= Special cases =
== Transport message auto-transformations ==
== Transport message transformations ==
Some transports may not provide exactly the transport message received, but may transform it in some way. In such case, the OPC UA PubSub sniffer will not "see" the very original message as received, but will only be provided and see the transformed message data. This can happen, for example, if the transport provides and option to decompress the data.
 
 
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== Security and sniffing ==
== Security and sniffing ==
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Revision as of 08:48, 14 August 2022

Introduction

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Capture types

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Individual capture types

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If the transport message cannot be parsed as an OPC UA PubSub message, the TransportMessage is the only capture emitted for the message. Otherwise, there is a NetworkMessage capture emitted following the TransportMessage, containing the network message header information specific to OPC UA PubSub. In special cases (such as with non-standard OPC UA PubSub extensions), there can even be more NetworkMessage captures for one TransportMessage.

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Capture type groupings

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Capture type groupings
Name Display Name Description
NetworkTraffic Network Traffic A grouping of capture types. Contains all network traffic messages.
AllPubSubMessages All PubSub Messages A grouping of capture types. Contains all OPC UA PubSub (terminal) messages.
AllDataSetMessages All DataSet Messages A grouping of capture types. Contains all dataset messages (parsed and unparsed).
AllDiscoveryMessages All Discovery Messages A grouping of capture types. Contains all discovery messages (probes and announcements).
AllDiscoveryProbes All Discovery Probes A grouping of capture types. Contains all (parsed and unparsed) discovery probe messages.
AllDiscoveryAnnouncements All Discovery Announcements A grouping of capture types. Contains all (parsed and unparsed) discovery announcement messages.
All All A grouping of capture types. Contains all message types (non-terminal and terminal).

Terminal and non-terminal messages

The capture types denote either non-terminal or terminal messages.

non-terminal message
The message is further structured and can contain other non-terminal or terminal messages. Consequently, there can be more captures arising out of a single non-terminal message.
terminal message
The message is not structured (or cannot be parsed) to further sub-messages. No further capture will be emitted for the terminal message.

Parsed and unparsed messages

Normally, the capture mechanism parses all parts of the message that are necessary to collect the information provided by the message. When the message or its part is encrypted, it is possible that the capture mechanism will not be able to decrypt (and parse) the full message contents, but will still be able to determine the type of the message and some PubSub header information. Such case is indicated by one of the unparsed capture types.

For more information to when the unparsed capture types are used, see Security and sniffing.

Capture header

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Special cases

Transport message transformations

Some transports may not provide exactly the transport message received, but may transform it in some way. In such case, the OPC UA PubSub sniffer will not "see" the very original message as received, but will only be provided and see the transformed message data. This can happen, for example, if the transport provides and option to decompress the data.


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Security and sniffing

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Data capture with sniffing

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See also

Using OpcCmd Utility as OPC UA PubSub Sniffer