RPF is often incorrectly defined as Reverse Path Filtering, particularlypaticularly when it comes to unicast routing. This is an understandable misinterpretation of the acronym in that when RPF is used with unicast routing as in RFC 3704 traffic is either permitted or denied based upon the RPF check passing or failing. The thought being that traffic is denied if it fails the RPF check and is therefore filtered, however as per RFC 3704 the correct interpretation is that traffic is '''forwarded''' if it passes the RPF check. Several examples of the proper usage can be seen in documents by [http://www.juniper.net/techpubs/software/junos/junos56/swconfig56-interfaces/html/interfaces-family-config15.html Juniper], [http://www.cisco.com/web/about/security/intelligence/unicast-rpf.html Cisco], [http://www.openbsd.org/faq/pf/filter.html#urpf OpenBSD], and most importantly RFC 3704 which defines the use of RPF with unicast.
While uRPF is used as an ingress '''filtering''' mechanism, it is affected by reverse path '''forwarding'''.
