Use this documentation with care! It describes
the heavily outdated version 5, which was actively
developed around 2010 and is considered dead by the
rsyslog team for many years now.
This documentation reflects the latest update of the previously existing (now removed) v5-stable branch. It describes the 5.10.2 version, which was never released. As such, it contains some content that does not apply to any released version.
To obtain the doc that properly matches your installed v5 version, obtain the doc set from your distro. Each version of rsyslog contained the version that exactly matches it.
As general advise, it is strongly suggested to upgrade to the current version supported by the rsyslog project. The current version can always be found on the right-hand side info box on the rsyslog web site.
Note that there is no rsyslog community support available for this heavily outdated version. If you need to stick with it, please ask your distribution for support.
Network stream drivers are a layer between various parts of rsyslogd (e.g. the imtcp module) and the transport layer. They provide sequenced delivery, authentication and confidentiality to the upper layers. Drivers implement different capabilities.
Users need to know about netstream drivers because they need to configure the proper driver, and proper driver properties, to achieve desired results (e.g. a Encrypting Syslog Traffic with TLS (SSL) [short version]).