Design Reference

Table Of Contents

• For a Layer 2 VSN with multicast, the BEB associates a data I-SID with the multicast stream

and a scope I-SID that defines the scope as a Layer 2 VSN. A multicast stream with a Layer 2

VSN scope can only transmit a multicast stream for the same Layer 2 VSN.

• For a Layer 3 VSN, the I-SID is associated with a customer VRF, which is also virtualized

across the backbone. Layer 3 VSNs are always full-mesh topologies. Layer 3 VSNs associate

one VRF per I-SID.

•

For a Layer 3 VSN with multicast, the BEB associates a data I-SID with the multicast stream

and a scope I-SID that defines the scope as a Layer 3 VSN. A multicast stream with a Layer 3

VSN scope can only transmit a multicast stream for the same Layer 3 VSN.

• For IP shortcuts with multicast, the BEB associates a data I-SID with the multicast stream and

defines the scope as Layer 3 Global Routing Table (GRT). A multicast stream with a scope of

Layer 3 GRT can only transmit a multicast stream for the Layer 3 GRT.

Encapsulating customer MAC addresses in backbone MAC addresses greatly improves network

scalability (no end-user C-MAC learning is required in the core) and also significantly improves

network robustness (loops have no effect on the backbone infrastructure).

The following figure shows the components of a basic SPBM architecture.

Figure 32: SPBM basic architecture