Document URL: https://access.redhat.com/documentation/en-us/openshift_container_platform/3.6/html-single/installation_and_configuration/#using-flannel

Section Number and Name: 

Describe the issue: Flannel documentation can be improved dramatically.

Suggestions for improvement: 
* Flannel does require port security to be disabled on the ports involved in container traffic and it is missing how to disable port security on port basis
* There is no explanation about flannel configuration (etcd injected, etc.)
* Missing iptables rules to make flannel work
* Explanation about pod network and services network in flannel (check this BZ https://bugzilla.redhat.com/show_bug.cgi?id=1473858)

Additional information: 
OCP on OSP ref. arch. contains some improvements that can be used in the official documentation.