14.4. Interoperability Status

The existence of standards by itself does not guarantee interoperability. Consider, for example, SONET BLSR and SDH MSpring standards. Several years after being standardized, no interoperable implementations of BLSR/MSpring from different vendors can be found. The best way to ensure interoperability is to conduct trials involving multiple vendors to uncover problems in early specifications and promote multivendor interworking. In this regard, some significant optical control plane interoperability trials have occurred:

• OIF UNI interoperability trial: In the summer of 2001, the OIF sponsored an UNI interoperability trial involving twenty-five different vendors. The vendors underwent interoperability testing in the interoperability laboratory at the University of New Hampshire. Later, there was a public demonstration of interoperability at SUPERCOMM 2001 where the vendors successfully demonstrated UNI-N (network) and UNI-C (client) implementations to dynamically provision optical network services between clients. It is worth noting that the reference model used for this interoperability event was a subset of what later became UNI 1.0.

  This interoperability event was a valuable experience for the equipment vendors, as well as the service providers. On the standards front, it helped in the refinement of OIF UNI 1.0 specification. It also helped in resolving certain issues related to the IETF GMPLS signaling specifications.

• OIF NNI interoperability trial: In the spring of 2003, the OIF conducted an NNI interoperability trial involving more than a dozen vendors. Both NNI routing and signaling were demonstrated. The NNI routing was based on extensions to OSPF-TE, and NNI signaling was based on GMPLS RSVP-TE. This trial demonstrated interdomain control, with multiple control domains represented by routing and signaling controllers (see Chapters 5 and 12).

• IETF GMPLS interoperability survey: A few multivendor GMPLS interoperability trials have been conducted. A number of vendors have also conducted private interoperability testing. As a part of the standardization process, the IETF conducted a GMPLS signaling implementation survey in which participants were asked to report the status of their implementation. A total of twenty-five participants, including equipment vendors, software vendors and service providers, responded [Berger+03]. From these responses it appears that GMPLS signaling implementation is making steady progress, although the recent telecom downturn may have slowed the pace a bit.

With regard to the ITU-T standards, multivendor interoperability trials are not a prerequisite for their progress. But given that the OIF implementation agreements are architecturally close to the ITU-T models, the OIF interoperability demonstrations serve as (limited) demonstrations of ITU-T standards.