Out of the box, Maven 3 only supports file:, http: and https: as transport protocols. Maven 2 adds scp: to this list.
To deploy a site with a non-built-in protocol, you need to add the corresponding wagon provider.
You can add it either as a global extension, or declare it at as a dependency of the site plugin:
<project> ... <build> <pluginManagement> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-site-plugin</artifactId> <version>3.0</version> <dependencies> <dependency><!-- add support for ssh/scp --> <groupId>org.apache.maven.wagon</groupId> <artifactId>wagon-ssh</artifactId> <version>1.0</version> </dependency> </dependencies> </plugin> </plugins> </pluginManagement> </build> ... </project>