The Internet and Its Protocols

9.2 MPLSFundamentals 393

9.2.5 Hierarchies and Tunnels

MPLS allows for LSPs to be nested or tunneled. This mechanism is useful for

allowing many LSPs to be treated in the same way in the core of the network

while preserving their individuality at the edges. Doing this enhances the scalability

of LSRs in the core of the network and significantly improves the manageability of

connections across the network.

Tunnels like the one between LSR W and LSR Z in Figure 9.6 may conven-

iently be presented to the routing protocol as virtual routing adjacencies or

Forwarding Adjacencies (FAs). This allows ...