Merging Service Provider Networks#

Markus Jungbluth, Bastian Hoss (Xantaro)

• Why: German SP market consolidation makes network merging a recurring challenge. The talk covers three integration approaches (NNI, Inter-Provider RFC 4364 Options A/B/C, Carrier-of-Carrier VPNs), explains why they're all "quick fixes" leaving networks administratively separate, and shows how Seamless MPLS builds real bridges — plus a novel ISIS LSDB-simulation technique for pre-merger testing.
• What: A technical walkthrough of IP/MPLS network integration post-acquisition. Key challenges addressed: low-scale access devices (~500–2k FIB) becoming the weakest link when IGPs merge, route summarization conflicting with MPLS label distribution (which relies on exact-match /32 or /128), and harmonizing metric values/IGP settings. The lab technique: exported ISIS LSPs from both networks, manipulated them to simulate a merged LSDB, and transmitted it to a DUT via a customized ISIS software implementation — proving the DUT wouldn't fail post-merger without touching production.
• How: BGP-LU (BGP Labeled Unicast) distributes transport labels via BGP, allowing low-scale devices to participate with a default route + filtered BGP-LU routes instead of full IGP/LDP. This separates service and transport planes, enabling Seamless MPLS scaling to 100,000+ nodes. The toolbox: BGP-LU/BGP-CT/BGP-CAR for IGP-independent label distribution, LDP/RSVP-TE/SR for IGP-specific, and SR-TE for traffic engineering. Merging IGPs is recommended as an opportunity to implement Segment Routing (Flex Algo, TI-LFA, SR-TE).
• Where applicable: Service providers going through M&A or building multi-domain networks. The Seamless MPLS toolbox and low-scale-device separation patterns apply to any large network with heterogeneous device capabilities. Xantaro-specific deployment experience but the techniques are standards-based and broadly documented.