Problems

Conclusion - Since 2002, the MPLS and Frame Relay Alliance has tested and publicly demonstrated different aspects of MPLS interoperability. In a total of six large multi-vendor test events, the participating vendors verified many different MPLS protocols for multi-vendor interoperability - from basic signalling to different flavors of Layer 2 and Layer 3 VPN services as well as DiffServ traffic engineering.

The interoperability event at MPLS World Congress 2005 reassures us that MPLS Layer 2 Ethernet-based VPN implementations are ready for large-scale deployments with many customers in a similar way to Layer 3 VPNs. Of course, each of these two solutions has its particular applications, inherent strengths and weaknesses which are well-known. In both cases, the IETF still continues to develop recommendations (see RFC2547bis, and the battle between BGP-based and LDP-based VPLS).

The more MPLS becomes a complete set of protocols suitable for a multitude of applications, the more we recognize how many work areas still remain to be addressed. As an example, it was quite surprising to notice that there were still issues with the interpretation of the basic LDP standard defined four years ago. At one of the first interoperability events of the MFA in 2003, an urgent need for implementation agreements was noted in order to reduce the amount of protocol options. This statement still holds, and implementation agreements defining use cases are more important than ever.

MPLS LSP ping and traceroute are a different topic. The corresponding internet draft still undergoes regular changes - which is the nature of an internet draft -, and vendors implement different incompatible versions. We contacted the draft authors; they hope that the next draft (number 8) will be fairly mature and might go to last call in March. There is hope that LSP ping and traceroute implementations will work more reliably in heterogeneous environments at the next MFA interoperability test event.

Despite of these small issues, Multi-Protocol Label Switching has grown to support a full set of standardized and interoperable VPN types - making MPLS way more flexible than network technologies of the past. A vast number of vendors implement MPLS by now, and the majority of carriers worldwide uses MPLS as the foundation for their IP and layer 2 service backbones.

The MPLS & Frame Relay Alliance and the supporting test labs, UNH-IOL and EANTC, are proud that the series of interoperability test events conducted since 2001 have been able to improve interoperability dramatically.