With more and more CableLabs member operators deploying or preparing to deploy ITU-T-based passive optical networking (PON) technologies such as XGS-PON, interoperability of equipment from different vendors is more important than ever. One well-known source for the lack of cross-vendor interoperability of XGS-PON equipment stems from differing implementations of the ONU Management Control Interface (OMCI) — primarily specified by ITU-T Recommendation G.988.
Last year, the CableLabs Common Provisioning and Management of PON (CPMP) working group set out to tighten some of the gaps in G.988, via the publication of the first version of the Cable OpenOMCI specification. This specification aims to enumerate the set of management elements from G.988 that are most important to CableLabs member operators and clarify how those elements must be supported in XGS-PON equipment intended for sale to those operators.
At a recent XGS-PON Interop·Labs event at CableLabs, multiple suppliers of PON optical line terminal (OLT) and PON optical network unit (ONU) equipment exercised their gear’s ability to interoperate. It was the industry’s first opportunity to exercise equipment implementations conformant to the requirements defined in the Cable OpenOMCI specification.
But the event, held April 28–May 1 in our Colorado labs, exercised more than just OMCI interoperability. It also included a continuation of the DOCSIS Provisioning of XGS-PON config file interoperability testing, first initiated during our February interop. Please see my blog post from March for a deeper description of the concept of DOCSIS Provisioning of XGS-PON and the scope of that event.
Supplier Participation in the XGS-PON Interop
Interoperability events enable participants to collaborate and problem-solve on specific technologies and goals. The participation of vendors is critical to advancing technology solutions for the entire industry.
Participants at our April Interop·Labs event included XGS-PON OLT suppliers — showcasing their OMCI and DOCSIS Adaptation Layer (DAL) implementations — as well as XGS-PON ONU suppliers, who showcased the OMCI aspects of their ONUs.
These XGS-PON OLT suppliers included Calix, Ciena and Nokia. In particular, Calix tested using their E7-2 OLT and DPx DAL. Ciena brought their Tibit MicroPlug OLT, MCMS controller and DAL system. And Nokia tested using their Lightspan MF-2 OLT and Altiplano controller. While the primary focus of the event was on XGS-PON technology, Ciena also brought their pre-production 25GS-PON OLT and 25GS-PON ONU, and demonstrated DOCSIS provisioning of that equipment, as well as traffic forwarding through it.
In addition to the OLT supplier participants, XGS-PON ONU suppliers in attendance included Askey, Cambridge Industries Group, Hitron, MaxLinear, Sagemcom and Sercomm. While Sagemcom brought an ONU embedded in a residential gateway, most suppliers brought bridging ONUs. Numerous ONUs from additional suppliers (including Calix, Ciena/Tibit and Nokia) were also on hand for interested OLT vendors to test with their OLT and DAL implementations.
The XGS-PON OMCI Test Cases
The OMCI test plan executed during the event was based on the requirements defined in the I01 version of the Cable OpenOMCI specification. Interested OLT and ONU suppliers met over the course of several weeks prior to the event to define the test cases that would be included in the interop test plan.
Following the general contents of the Cable OpenOMCI specification, the following test cases were defined:
- The MIB upload component of OMCI configuration management
- Create and get methods of OMCI configuration management
- Performance monitoring via OMCI
- ONU software image download
- ONU software image activation
During the first three test cases, the lab’s 100GE traffic generation system was used to transmit and receive traffic via a given OLT and ONU combination under test. And during each of the five test cases, an XGS-PON analyzer or OMCI debug capabilities of the OLT were used to capture and examine the message exchanges between the ONU and OLT. One participating OLT vendor indicated that, during the event, they tested with 12 different ONU models, inspecting close to 100 OMCI management elements for each ONU.
The results of the interop testing were encouraging and showed that the participating suppliers have already begun implementing the requirements of the Cable OpenOMCI specification in their software. As expected, the testing also uncovered additional OMCI interoperability issues. Those issues will inform the next set of work items for the CPMP working group to tackle.
New Issues Bring New Fixes
With a wide array of OLT and ONU vendor implementations on hand at the event, new issues were bound to be discovered — which is exactly why we hold interoperability events.
Now, the CPMP working group will discuss our findings and prioritize solutions for them via an engineering change process to the Cable OpenOMCI specification. Fixes for the simpler issues will likely be included in the upcoming release of the I02 version of the spec. More complex issues may take more time for the working group to solve and will therefore be addressed in a later version of the spec.
Join Us Next Time
CableLabs is planning two more PON Interop·Labs events this year, with the next event scheduled for the week of Aug. 4. Stay tuned for more details.
The August event will provide an opportunity for OLT and ONU suppliers to return to test interoperability based on compliance with an anticipated I02 version of the Cable OpenOMCI specification. We also welcome OLT suppliers to return to exercise their DAL solutions for ONU and config file interoperability.