These solutions are meant to be implemented by
routers at the core of the Internet, the edge of the Internet, or both. These
solutions generally face more hurdles to deployment, but can be the most
effective since they can stop spoofing packets from even reaching end-hosts.
Seldom can router-based mechanisms be ported to end-hosts. (Routers
may deploy some reactive mechanisms such as tracing where a malicious
packet is from. However, reactive mechanisms are triggered only after
spoofing packets are detected, so in this article we focus on router-based
mechanisms with the main objective of preventing the delivery of spoofing
packets.)