Annex C (normative) OPC UA Mapping to mDNS ToC Previous Next

C.3 DiscoveryUrl Mapping ToC Previous Next

An DiscoveryUrl has the form:

scheme://hostname:port/path

scheme: the protocol used to establish a connection.

hostname: the domain name or IPAddress of the host where the Server is running.

port: the TCP port on which the Server is to be found.

path: additional data used to identify a specific Server.

Table 70 – DiscoveryUrl to DNS SRV and TXT Record Mapping

URL Field Mapping
scheme The scheme maps onto SRV record service field.
The following mappings are defined at this time:
   opc.tcp   _opcua-tcp._tcp.
   opc.wss   _opcua-tls._tcp.
   https   _opcua-https._tcp.
The first two are OPC UA service names assigned by IANA.
Additional service names may be added in the future.
The endpoint shall support the default transport profile for the scheme.
hostname The hostname maps onto the SRV record target field.
If the hostname is an IPAddress then it shall be converted to a domain name.
If this cannot be done then LDS shall report an error.
port The port maps onto the SRV record port field.
path The path maps onto the path string in the TXT record (see Table 69).

Suitable default values should be chosen for fields in a SRV record that do not have a mapping specified in Table 70. e.g. TTL=86400, class=IN, priority=0, weight=5

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