There are two common methods for transporting multicast packets within an MPLS-based Layer 3 VPN: Generic Routing Encapsulation (GRE) with Protocol Independent Multicast (PIM) (also known as "draft-rosen") Label Switched Multicast (LSM) There's also a third method which uses Resource Reservation Protocol-Traffic Engineering (RSVP-TE) but I'm not going to get into that one. In this first post in a series on LSM, I'll describe how draft-rosen works, how LSM works, and then compare and contrast ...
