Questions about draft-sajassi-l2vpn-vpls-bridge-interop-00

["Busschbach, Peter B (Peter)" <[e-mail]>]

1) Section 8 of draft-sajassi-l2vpn-vpls-bridge-interop-00 says "And if the CE devices belonging to an ESI are IEEE bridges, then a partial-mesh of PWs can cause broadcast storms in the customer and provider networks"

I understand that when a MAC address becomes unreachable, new messages destined for that MAC address will be replicated over all links, but does that qualify as a broadcast storm? Or is there more to it than that?


2) The next sentence in section 8: "Furthermore, it can cause multiple copies of a single frame to be received by the CE and/or PE devices"

How can that happen?


3) A few paragraphs down: "Therefore, the detection time may be longer than the detection time needed for loop prevention inside the customer network"

Apparently, partial mesh can lead to a loop in the customer network. I guess this is a consequence of the interworking between STP and VPLS, but don't understand the details. Is this easy to explain or should I take a course in STP?


4) Section 10 "For example, if a service instance is associated with four CEs at four different sites, then the maximum number of provider bridges (or PEs), that need to participate in that customer MAC address learning, is only three regardless of how many PEs are in the path of that service instance."

I don't understand that. If four CE2 are connected to four PEs with a full-mesh of PWs between the PEs, don't all four PEs need to participate in MAC address learning?


That's all (for now).

Peter