`network_transport` should be `ip_protocol`

**Describe the bug**
The term `network_transport` is not always clear. This field is intended to identify the IP protocol identified in a network message, a more accurate and meaningful field name would be `ip_protocol`, and the numeric companion field `ip_protocol_number`.

Search the documentation for occurrences of `network_transport` and its numeric companion field. Review the surrounding field definitions to confirm that they identify the IP protocol, then update the documented names to `ip_protocol` and `ip_protocol_number`. Done means the old names no longer remain in the relevant documentation.

Written by the indexing model from the issue text.