The Multi-Source Agreement (MSA) for open reconfigurable add-drop multiplexers (ROADM) group expects to publish its second release in the coming months. The latest MSA specifications extend optical reach by including line amplification and adds support for flexible grid and lower-speed tributaries with OTN switching.
The Open ROADM MSA, set up by AT&T, Ciena, Fujitsu and Nokia, is promoting interoperability between vendors’ ROADMs by specifying open interfaces for their control using software-defined networking (SDN) technology. Now, one year on, the MSA has 10 members, equally split between operators and systems vendors.
Orange joined the Open ROADM MSA last July and says it shares AT&T’s view that optical networks lack openness given the proprietary features of the vendors’ systems.
“As service providers, we suffer from lock-in where our networks are composed of equipment from a single vendor,” says Xavier Pougnard, R&D manager for transport networks at Orange Labs. “When we want to introduce another vendor for innovation or economic reasons, it is nearly impossible.”
This is what the MSA group wants to tackle with its open specifications for the data and management planes. The goal is to enable an operator to swap equipment without having to change their control by using a common, open management interface. “Right now, for every new provider, we need IT development for the management of the [network] node,” says Pougnard.
As service providers, we suffer from lock-in where our networks are composed of equipment from a single vendor. When we want to introduce another vendor for innovation or economic reasons, it is nearly impossible.
The Open ROADM MSA has published two data sets as part of its Release 1.2. One set tackles 100-gigabit data plane interoperability by defining what is needed for two line-side transponders to talk to each other. The second set of specifications uses the YANG modelling language to allow the management of the transponders and ROADMs.
The group is now working on Release 2.0 that will enable longer reaches and exploit OTN switching. The specifications will also support flexgrid whereas Release 1.2 specifies 50GHz fixed channels only. Release 2.0 is expected to be completed in the second quarter of 2017. “Service providers would like it as soon as possible,” says Pougnard.
Pougnard highlights the speed of development of an open MSA model with new releases issued every few months, far quicker that traditional standardisation bodies. It was this frustration with the slow pace of development of the standards bodies that led Orange to join the Open ROADM MSA.
Orange stresses that the Open ROADM will not be used for all dense wavelength-division multiplexing cases. There will be applications which require extended performance where a specific vendor's equipment will be used. “We do specify the use of an FEC [forward error correction] in the specification but there are more powerful FECs that extend the reach for 100-gigabit interfaces,” says Pougnard. But the underlying flexibility offered by the MSA trumps performance.
AT&T detailed in December a network demonstration of the Open ROADM technology. The operator used a 100-gigabit optical wavelength in its Dallas area network to connect two IP-MPLS routers using transponders and ROADMs from Ciena and Fujitsu.
Orange is targeting its own lab trials in the first half of this year using a simplified OpenDaylight SDN controller working with ROADMs from three systems vendors. “We want to showcase the technology and prove the added value of an open ROADM,” says Pougnard.
Orange is also a member of the Telecom Infra Project, a venture that includes Facebook and 10 operators to tackle telecom networks from access to the core. The two groups have had discussions about areas of possible collaboration but while the Open ROADM MSA wants to promote a single YANG model that includes the amplifiers of the line system, TIP expects there to be more than a single model. The two organisations also differ in their philosophies: the Open ROADM MSA concerns itself with the interfaces to the platforms whereas TIP also tackles the internal design of platforms.
Coriant, which is a member of TIP and the Open ROADM MSA, is keen for alignment. "As an industry we should try to make sure that certain elements such as open API definitions are aligned between TIP and the Open ROADM MSA," says Uwe Fischer, CTO of Coriant.
Meanwhile, the Open ROADM MSA will announce another vendor member soon and says additional operators are watching the MSA’s progress with interest.
Pougnard stresses how open developments such as the ROADM MSA require WDM engineers to tackle new things. “We have a tremendous shift in skills,” he says. “Now they need to work on the automation capability, on YANG modelling and Netconf.” Netconf - the IETF’s network configuration protocol - uses YANG models to enable the management of network devices such as ROADMs.