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SDN promises real-time UC app, network dialogue

The promise of SDN for real-time communications is to give UC apps the network paths and priority they need to eliminate performance problems ---- and development is part way there.

LAS VEGAS -- The ability for networks and unified communications applications to talk to each other in real time will make software-defined networking the answer for real-time communications. But understanding how SDN can configure and manage real-time like voice and video will take time.

Terry Slattery, principal architect of network engineering consultancy NetCraftsmen, told a crowd of network and telecom engineers at Interop that SDN can automate the process of making sure voice and video get the priority network resources they need because they are highly sensitive to network performance. But SDN for UC isn't ready for prime time yet, he added.

Vendors including HP Networking and NEC are focused on SDN for UC, working with Microsoft to software-enable network communication with Microsoft's rebranded Skype for Business (still called Lync by most Interop attendees). Microsoft released an SDN API last year to help identify critical issues in its Lync UC platform.

Cisco is taking a different route and has enabled device tagging in its Application Policy Infrastructure Controller (APIC) that works with legacy network equipment, Slattery said.

Device tagging allows enterprises to group devices by function or role rather than box by box to make the network easier to program.

Traditional network limitations for UC apps

Traditional networks have static configurations that aren't responsive to the individual needs of applications. Because legacy networks have poor visibility into real-time traffic, they can't tell applications about network changes that will affect voice and video delivery, Slattery said.

 On the other side of the equation, "Tech folks have been so trained in using manual CLI [command line interface] commands that they're worried about using automated tools because they might break the network," Slattery said.

The introduction of SDN will be valuable to UC using capabilities like bidirectional communications between applications and the network, fast automated configuration, built-in security and new forwarding-path selection, Slattery said.

Representational State Transfer (REST) application program interfaces (APIs) can execute common operations to enable centralized SDN controllers and applications to talk to each other via a UC controller, he added.

"We want to dynamically select a media traffic path based on media traffic type and driven by current network loading and characteristics," Slattery said. SDN policies can handle what to do when the network is oversubscribed. They can tell the UC controller to adjust the codec, deny a call, drop packets or move traffic to another path.

The use of SDN for UC applications can enable dynamic Quality of Service that can apply a classification when a call is set up, for example. Call admission control (CAC) can be integrated across multiple UC applications to make sure real-time media traffic isn't routed over a congested path.

SDN UC use cases

Since SDN is still emerging, today's main UC use case for SDN is where the network can self-configure in real time because the UC app can talk to the network about its needs, said Nemertes UC analyst Irwin Lazar.

"The app can basically tell the network it's about to send a phone call out and ask if there's something happening it needs to know about," Lazar said. "This is especially useful over wireless networks where you have more congestion."

The other use case is leveraging SDN application program interfaces (APIs) to pull traffic information so they can ping different network components and find out what's going on for certain kinds of flows for specific applications like voice and video. "Some vendors are looking at using that to be able to do network management without having to put probes out on the network," Lazar said.

How to move forward with UC SDN

Some network professions worry that automating the network will eventually cost them their jobs. Slattery disagreed, adding that more must be done to make UC SDN valuable to the enterprise.

"The documentation [from vendors] is sometimes vague, so someone is going to need to figure out how this works," he said. "And has anyone said anything about monitoring and troubleshooting? No, we'll bolt that on at the end.

"Vendors need to spend more time thinking about how to do that. All of this is in transition and the use cases are helping define required functionality."

Slattery told enterprises not to change their network architecture plans, despite SDN's promise to improve real-time communications. Instead, he suggested enterprises put pressure on their vendors to lay out their SDN plans for UC applications.

To get familiar with SDN, Slattery recommended enterprise networking and applications teams work together to figure out SDN's UC advantages. To start, they can test SDN in a small part of the network. If it works, they can expand SDN's reach.

Next Steps

What to do with needy UC apps? SDN could hold the answer

Why UC could be the SDN's killer app

REST APIs in SDN represent new territory for network engineers

Five reasons IT leaders aren't ready to buy SDN

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