NFV Tests & Trials

AT&T Testing Virtualized GPON

Having already deployed NFV in almost 70 of its central offices, AT&T is now testing an approach to virtualizing its optical access, with the intent of reducing costs and adding flexibility. Tom Anschutz, Distinguished Member-Technical Staff for AT&T, told the audience at Light Reading's Carrier SDN Networks event this week the company's approach will also work for copper-based G.fast networks and probably support cable DOCSIS networks as well.

AT&T Inc. (NYSE: T) presented its virtualization plan for Gigabit passive optical networks to the Open Compute Project earlier this year and it was accepted as a working project, Anschutz said, in addition to being demonstrated at the upcoming Open Networking Summit in June. The idea is for this to be an open industry-wide approach.

Bringing virtualization and its benefits -- lower-cost hardware, greater flexibility and programmability and faster service delivery on open systems -- to the access network is important because that's where much of AT&T's costs lie.

"Talking about big routers is sexy but let's face it, all the money goes here," he said, indicating the access network. "If I make a difference in this part of AT&Ts network, I get to pull the big lever in terms of the economic game to the company."

The AT&T engineer, introduced by Heavy Reading Senior Analyst Sterling Perrin as a co-author of AT&T's Domain 2.0 manifesto, gave the audience a detailed look into what he calls "Refactoring Communications for SDN and NFV." That process focuses on looking inside today's special-purpose and proprietary boxes to see how their functions can be broken down and handled by IT-grade data center infrastructure. (See AT&T Puts SDN/NFV in Driver's Seat.)

The Open Compute Project is one of several industry groups holding workshops at Light Reading's Big Telecom Event on June 9-10 in Chicago. Get yourself registered today or get left behind!

In the case of GPON access, the open line terminals that provide much of that functionality are most commonly deployed today in central offices, not in the outside plant, although the latter is still a candidate for virtualization, Anschutz said. Most of the OLT's functions can be directly and relatively easily mapped to standard NFV infrastructure, he said.

"I've got basic switching and routing I can do in my fabric, I've got management I can do in x86 [standard off-the-shelf computing]," he commented. Line cards, interfaces to the fabric and processing can be done using standard fabric switches, storage, servers and Ethernet connections.

"The only thing here that I couldn't do in standard data center infrastructure is to create the physical layer for PON," Anschutz said. That physical layer, the PON MACs, will require "something new, I don't get that in a top-of-rack switch today, so let's do something about that."

The GPON Phy on its hopefully new platform is mapped to the NFV fabric, he says, using separate paths for the forwarding of data and control. The forwarding data is routed to the Internet through a series of what he calls "spine and leaf switches" through a virtual broadband network gateway and out to the metro core. Control and management via SDN also are handled by the same standard hardware on a different path.

This approach looks very much like that software architecture use for SDN control of standard top-of-rack switches in the data center environment, Anschutz says. It uses OpenFlow in the abstraction layer between the physical network and the upper layers, including an OpenFlow agent and controller, along with Netconf/Yang to handle configuration. AT&T can then run standard IT applications on top of this virtualized access platform.

"Based on my IT people telling me what they'd rather see it look like, I made it look like a big Ethernet switch," Anschutz said. "I can make G.fast look like a big Ethernet switch and I think I could make DOCSIS look like a big Ethernet switch and the IT people wouldn't care. So when they write the app that goes at the top that does 802.1X authentication or IGMP snooping or another SDN control function, they would be written once and work on GPON, XG-PON and G.fast, and maybe DOCSIS. That is going to save me a load in IT costs."

What AT&T is testing for optical access builds on what it has already deployed in many central offices to support its NetBond service, which provides secure VPN connections to a wide variety of cloud services. (See AT&T Spotlights Early SDN Efforts, AT&T Adds HP to Cloud Ecosystem, SDN Powers AT&T, IBM On-Demand Cloud Connections and AT&T NetBond Getting Amazon Ties.)

Prior to talking specifically about optical access, Anschutz presented a more general view of breaking down network gear into virtualizable parts, based on AT&T's adopting the approach to infrastructure that many Web 2.0 players are taking. All of this is being done in the name of business imperatives to make AT&T successful in 2020.

"We have to open our network, become modular and be able to allow not just ourselves but other people to program it," he said. "We have to simplify and scale and we think that NFV infrastructure and new operational paradigms borrowed from the Web 2.0 folks is a great way to get that done."

— Carol Wilson, Editor-at-Large, Light Reading

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brooks7 5/15/2015 | 4:35:45 PM
Re: Testing? "Saying something like "virtualized GPON" makes little sense since the bulk of the cost and complexity is the MAC layer which no one is virtualizing. "


The MAC is actually pretty simple and about the same complexity is an Ethernet MAC.  The Optics on the OLT side are a pain, only the 3 wavelength version on the ONT side have any challenges at all.

I think they are talking about virtualization at the ONT.  That would be pretty simple if you create the actual GPON function as an Optical module attached to a MAC with a single Ethernet Connection.  You could restrict the OMCI to inside that module and manage just the MAC and the Ethernet Interface.

After that, its just a computer.  Run whatever software on it you want.

But here is the thing.  None of that is the real cost of even the electronics of a GPON network as deployed at something like FiOS.  It is all in the electro-mechanical and constrcution.  I think you could make the electronics (not the optics) inside the ONT costs 0 and it is still a challenge.  


cnwedit 5/15/2015 | 2:13:38 PM
Re: Testing? Anschutz would disagree that they aren't testing anything and most of the folks in the room would as well. This presentation was the hottest topic of the day. 

He admitted they need something new for the MAC - a standalone piece of hardware. But being able to virtualize the other functions is a significant step because if they can do that, there is no need for siloed applications for different methods of access. 

He also showed the same approach to disassembling gateway routers that connect data center infrastructure to the WAN, breaking down functions and using IT-grade hardware in place of highly specialized boxes. 

I guess it's easy to be dismissive at this stage but it sure comes across as real. 
dwx 5/15/2015 | 1:58:51 PM
Testing? Reading the article it doesn't sound like they are testing anything.   Saying something like "virtualized GPON" makes little sense since the bulk of the cost and complexity is the MAC layer which no one is virtualizing.   Really what they are doing is trying to virtualize some of the management functions of the OLT, which makes sense.   At its lowest layer an OLT today just converts GPON MAC PHY to Ethernet or Ethernet/IP.   The GPON MAC PHY is specialized hardware, there isn't a whole lot you can virtualize there.  If you really wanted to commoditize it end to end you should have used Active Ethernet... 
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