No self-respecting optical equipment vendor can afford to be without a well-considered strategy for software defined networking (SDN). Over the last 18 months or so, most of the major and second-tier vendors have announced how they intend to approach software control of the optical layer in carrier transport networks – which we will call transport SDN to distinguish it from the more well-developed application of SDN in data centre network environments.
Talking about transport SDN is one thing; however, deploying it in the real world is quite another. Last year, market research firm Infonetics found that while more than three-quarters of service providers surveyed said they plan to deploy transport SDN at some point, only one third said the equipment vendors’ SDN strategies will play a critical role in their selection of equipment and suppliers in the present day.
While most carriers are still metaphorically kicking the tyres of SDN by engaging in research experiments and field trials, a pioneer has emerged. Asia-Pacific wholesale service provider Pacnet has launched what it says is the first large-scale commercial service to be based on transport SDN principles and it is enabled by the Open Transport Switch (OTS) software from optical systems vendor Infinera.
An existing customer of Infinera, Pacnet’s optical transport network is based on the vendor’s DTN-X packet-optical transport platform. The network itself is a 100G optical network that links data centres in 15 cities across Asia via 46 000km of optical fibre. The carrier also owns the EAC-C2C submarine cable system with 21 cable landing stations, making the network extremely meshed and resilient.
‘In the context of this announcement, that mesh network becomes very important for us because it allows alternative paths through the network,’ said Geoff Bennett, director of solutions and technology at Infinera. ‘Pacnet has this nice meshed core network and they’re basically enabling customer to have more dynamic access to it.’
Pacnet has integrated Infinera’s OTS software into what it calls the Pacnet Enabled Network (PEN), which is a service delivery platform based on SDN principles. The earlier versions of PEN were software controlled at the Ethernet layer. The new service, PEN 3.0, is a transport SDN-enabled version of this concept, allowing the optical paths on the network to be automated.
Bennett said: ‘In the past, although the Infinera network gave Pacnet a significant advantage in terms of flexibility, the process from a Pacnet point of view still had a lot of human intervention. The customer would call Pacnet, they’d request a circuit, Pacnet would use the advantage of Infinera’s network, they’d turn up that capacity more quickly, but there was still a human in the process. The big difference with this new approach is that we can eliminate that.’
Instead Pacnet’s customer gains access to a self-service portal to book capacity on the network. The customer can see end points, they can see the bandwidth that’s available, and they can express how long they want to use that service.
Bennett likens it to calling a travel agent to book a flight. Today most people prefer to go online, where they can quickly compare a number of airlines and within five minutes get different prices from different airlines, allowing them to find a cheaper price for exactly the same service. The self-service portal is the same, he says. It allows the customer a lot more control, and they’re able to get what they need at a lower price, and probably a lot quicker.
The carrier can retain fine control over the services delivered using policy control in the SDN application. Bennett explained: ‘If this customer is asking for, say, gigabit levels of bandwidth, that’s fine, the portal will tell them it’s available or not. If they’re asking for tens of gigabits of bandwidth, at that point the phone rings on the travel agent’s desk again and they can step in.’
It’s important to take a pragmatic approach when rolling out new services, he says. ‘The whole point of this gradual evolution of rolling out a service like this is to find out if there’s value for the customer. If you find out that 90 per cent of the transactions are sub-one gigabit per second and can therefore can be fulfilled with a self-service portal, you can save yourself a fortune. But if you hold out and say you want to deal with 100 per cent of transactions in a self-service portal, you may never get there.’
Using the self-service bandwidth portal can cut service provisioning times down to minutes instead of weeks or even months and is integrated with the billing system. From Pacnet’s point of view, the automation of key processes helps them to offer a more competitive service, generate new revenues, tap into underutilised resources on the network, and increase customer retention all while lowering operational costs.
There’s an important caveat, however. ‘One of the provisos has to be that you have to have spare bandwidth in the network. If there isn’t any spare capacity on the route, the service provider would have to call up and order some equipment, then obviously at that point it becomes more like two weeks,’ he said.
Just another control plane
Pacnet has deployed the Infinera OTS into its existing DTN-X production network by running in Hybrid Control mode, which allows new services to set up new bandwidth connections under SDN control, while existing production services continue to operate using their Infinera Digital Network Administrator (DNA) network management system.
‘One of the things I like to point out to people is that SDN is just another control plane. There’s nothing magical about it,’ said Bennett. Ever since Infinera started shipping product in 2005, the company has used Generalised Multiprotocol Label Switching (GMPLS) as a control plane and touted what it calls ‘Instant Bandwidth’, the ability of the software to set up and tear down connections in minutes.
However, Bennett notes that GMPLS doesn’t have exposed application programming interfaces (APIs) that allow third-parties to communicate with the software, so if a service provider wants to do things with GMPLS, typically they would need a vendor proprietary management system and make the changes there.
He added: ‘I could show you wonderful things that we can do with our management system in terms of point-and-click-provisioning of services, making them re-routable, making them protected, there’s all sort of things you can do, but you’re doing it with our management system. What SDN allows you to do is, instead of a proprietary management system, we’re now allowing our switches to be controlled by a SDN controller.’ If you take this thought to its logical conclusion, this means a service provider no longer needs a propriety network management system to run the network any more, they could actually do it with the appropriate applications on an SDN controller.
The new OTS software, which is available now, is the piece that enables Infinera’s DTN-X optical switches to be managed by a third-party SDN controller. The control layer talks to the switch through open Web 2.0 APIs that have been created using a lightweight, modern software construct that abstracts the underlying transport network to make it easily programmable.
Initial applications
Other optical vendors have said they expect transport SDN to be deployed on the edges of the network first, because that is where the most variability in traffic patterns is usually found. As you move into the core, statistical multiplexing helps to smooth everything out, but this doesn’t happen to the same extent on the edges of the network.
For example, at Mobile World Congress in Barcelona earlier this month, Coriant carried out a demonstration in partnership with Nokia, where they used Nokia’s network traffic analytics in combination with Coriant’s Transcend SDN software to optimise the bandwidth allocation in a mobile backhaul network.
What Pacnet and Infinera have announced with the PEN 3.0 service is the polar opposite – software control of bandwidth on an ultra-long-haul core submarine network spanning the Pacific. Bennett is not surprised by this observation. ‘This won’t be the first conversation we’ve had where you say to me “Infinera’s giving me a completely opposite story to everybody else”. Honestly it’s for the same reasons that this always happens – we’ve got a capability in our hardware that other people don’t have.’
He is referring to Infinera’s 500G super-channel system, which is enabled by photonic integrated circuits (PICs). The PICs replace multiple discrete components with a single pair of indium phosphide chips, meaning that every Infinera line card ships with spare capacity already installed.
‘With most other people’s architectures, in fact every other architecture I can think of at the moment, their approach is a pay-as-you-grow model,’ said Bennett. ‘What happens is that, to turn up capacity between A and B, you go out and you buy a 100G transponder, an engineer installs it, you turn up that wavelength and now you make it available for services.
‘That model is slow but the reason that service providers have tended to force vendors to do it is they don’t want to buy transponders until they have a revenue-generating service demand that’s going to pay for it. But the end result is that their network may become less responsive. It may actually resist automation because if ever there is a process where you’ve got to call up an engineer and install a transponder that is going to resist automation by a control plane because there is a human operation in the process.’ he said.
One of the first enhancements Infinera made to its super-channel product was to allow customers to spread out the cost of buying 500 Gb/s wavelength of bandwidth when they might not need it all on day one. Bennett explained: ‘Instead of buying it all in one chunk, we install it all in one chunk – in other words the carrier does one set of wavelength planning, they have one visit by the engineer, but then they pay for the individual 100G wavelengths one at a time. With this approach you can have spare capacity in your network that could be controlled by a control plane but you’re not paying for it.’
This is the best of both worlds, he says. ‘You’ve got the pay as you grow model where you send engineers to install transponders, but you’ve also got instant bandwidth. That’s one of the reasons why our network architecture has always been very amenable to control by protocols like GMPLS or now by SDN.’
Virtualised photons
This trend is driven by the need to virtualise as many functions in the network as you possibly can, but one thing you can’t really virtualise is the production of photons, says Bennett. ‘Whatever is cranking out those photons has got to be a physical thing. What Infinera has been able to do is to give carriers a degree of flexibility on that physical thing that cranks out photons.’
Clearly if a carrier wants to have flexible control of its optical capacity then there needs to be a degree of flexibility built into that optical capacity. Unlike software control in the higher layers of the network, which optimally allocate packet-based traffic to the available capacity, transport SDN has the greatest potential value for carriers whose networks have an agile amount of capacity. In other words, the capabilities of the underlying hardware will influence what the software can do.
The interesting question is when other carriers will follow Pacnet’s lead. The research and education networks are at the front of the queue. One of Infinera’s customers is GÉANT, the pan-European research network for the education community in Europe. ‘They’re fascinated by the whole SDN thing,’ said Bennett. They have these designated set of customers which are the European research and education networks, and they desperately want to give those customers the option to control their own destiny. An SDN capability with a customer portal would be perfect for them.’
He added: ‘Quite rightly the point that we’re at now is that service providers are asking the questions, what am I going to use this for, what value would it be to me? In answering that question you have to look at their network. For example, if they’re predominantly a point-to-point network architecture, they probably don’t need to get involved in SDN. If they’ve got a highly meshed network with customers who are asking for more control, more visibility of their services, like Pacnet, then SDN is exactly what they need in order to innovate.’
