Lab 3 – SR-LDP Interworking

After the previous chapter, the network topology now employs two distinct MPLS forwarding mechanisms. The left side utilizes both SR-MPLS and LDP, while the right side operates solely on LDP. However, neither protocol utilizes the MPLS data-plane forwarding established by the other. Although the control-plane label distribution methods of SR-MPLS and LDP differ, their data-plane forwarding methods are the same. Both LDP and SR-MPLS eventually program the Label Forwarding Information Base (LFIB) and Forwarding Information Base (FIB) for MPLS-to-MPLS and IP-to-MPLS traffic forwarding, respectively. Hardware does not differentiate in forwarding traffic when utilizing one SR-MPLS label over the LDP label. This implies that routers running both SR-MPLS and LDP at the border of two domains should be capable of swapping incoming SR-MPLS labeled traffic with outgoing LDP labels, and vice versa.