What We Can Learn from Verizon’s SDN/NFV Paper

Verizon has just released a white paper on its SDN/NFV strategy, developed with the help of a number of major vendors, and the paper exposes a number of interesting insights into Tier One next-gen network planning.  Some are more detailed discussions of things Verizon has revealed in the past, and some new and interesting.  This document is over 200 pages long and far too complicated to analyze here, so I’m going to focus on the high-level stuff, and along the way make some comments on the approach.  Obviously Verizon can build their network the way they want; I’m only suggesting places where I think they might change their minds later on.

The key point of the paper, I think, is that Verizon is targeting improvements in operations efficiency and service agility, which means that they’ve moved decisively away from the view that either SDN or NFV are primarily ways of saving money on infrastructure.  This is completely consistent with what operators globally have told me for the last several years; capex simply won’t deliver the benefits needed to transform the business.  And, may I add, business transformation is an explicit Verizon goal, and they target it with both SDN and NFV.

On the SDN side, Verizon is particularly focused on the independence of the control and data planes (“media planes”, as Verizon puts it, reflecting the increased focus on video delivery).  This is interesting because it validates the purist SDN-controller-and-OpenFlow model of SDN over models that leverage software control of current switches and routers.  They also say that they are expecting to use white-box products for the switches/routers in their network, but note here that “white box” means low-feature commodity products and not necessarily products from startups or from non-incumbent network vendors.  It would be up to those vendors to decide if they wanted to get into the switch game with Verizon at the expense of putting their legacy product revenue streams at risk.

On the NFV side, things are a bit less explicit at the high level.  Verizon recognizes the basic mission of NFV as that of decoupling functional software from specific appliances to allow its hosting on server pools.

One of the reasons why the NFV mission is lightweight at the high level, I think, is that Verizon includes an End to End Orchestration layer in its architecture, sitting above both NFV MANO and the SDN controller(s).  This layer is also responsible for coordinating the behavior of legacy network elements that make up parts of the service, and it demonstrates how critical it is to support current technology and even new deployments of legacy technology in SDN/NFV evolution.

Verizon also makes an interesting point regarding SDN and NFV, in the orchestration context.  NFV, they point out, is responsible for deploying virtual functions without knowing what they do—the VNFs appear as equivalent to physical devices in their vision.  Their WAN SDN Controller, in contrast, knows that a function does but doesn’t know whether it’s virtualized or not.  SDN controllers then control both virtual and physical forms of “white box” switches.

One reason for this approach is that Verizon wants an architecture that evolves to SDN/NFV based on benefits, often service-specific missions.  That relates well with the point I made in yesterday’s blog about operators looking more at SDN or NFV as a service solution than as an abstract architecture goal.  All of this magnifies the role of the service model, which in Verizon’s architecture is explicitly introduced in three places.  First, as how an OSS/BSS sees the service, which presumably is a retail-level view.  Second, as the way of describing resource-behavior-driven cooperative service elements, and third (in the form of what Verizon calls “device models”) as an abstraction for the functional units that can be mapped either to VNFs or physical network functions (PNFs).  End-to-End Orchestration (EEO) then manages the connection of models and doesn’t have to worry about the details of how each model is realized.  This is a firm vote in favor of multi-layer, divided, orchestration.

Management in the VNF sense is accommodated in the Service Assurance function, which Verizon says “collects alarm and monitoring data. Applications within SA or interfacing with SA can then use this data for fault correlation, root cause analysis, service impact analysis, SLA management, security monitoring and analytics, etc.”  This appears to be a vote for a repository model for management.  However, they don’t seem to include the EMS data for legacy elements in the repository, which I think reflects their view that how a function is realized (and thus how it is managed) is abstracted in their model.

I do have concerns about these last two points.  I think that a unified modeling approach to services is both possible and advantageous, and I think that all management information should be collected in the same way to facilitate a unified model and consistent service automation.  It may be that Verizon is recognizing that no such unified model has emerged in the space, and thus are simply accommodating the inevitability of multiple implementations.

An interesting feature of the architecture on the SDN side is the fact that Verizon has three separate SDN controller domains—access, WAN, and data center.  This, I think, is also an accommodation to the state of SDN (and NFV) progress, because a truly powerful SDN domain concept (and a related one for NFV) would support any arbitrary hierarchy of control and orchestration.  Verizon seems to be laying out its basic needs to help limit the scope of integration needed.  EEO is then responsible for harmonizing the behavior of all the domains involved in a service—including SDN, NFV, and legacy devices.

Another area where I have some concerns is in the infrastructure and virtualization piece of the architecture.  I couldn’t find an explicit statement that the architecture would support multiple infrastructure managers other than that both virtual and physical infrastructure managers are required.  But does this multiplicity also extend within each category?  If not, then it may be difficult to accommodate multi-vendor solutions given that we already have proprietary management in the physical network device sense, and that the ETSI specs aren’t detailed enough to insure that a single VIM could manage anyone’s infrastructure.

My management questions continue in the VNF Manager space.  Verizon’s statement is that “Most of the VNF Manager functions are assumed to be generic common functions applicable to any type of VNF. However, the NFV-MANO architectural framework needs to also support cases where VNF instances need specific functionality for their lifecycle management, and such functionality may be specified in the VNF Package.”  This allows an arbitrary split model of VNF management, particularly given that there are no specifications for how “generic functions” are defined or how VNF providers can support them.  It would seem that vendors could easily spin most management into something VNF-specific, which could then complicate integration and interchangeability goals.

EEO is the critical element of the architecture overall.  According to the document, “The objective of EEO is to realize zero-touch provisioning: a service instantiation request — from the operations crew or from the customer, through a self-service portal – results in an automatically executed work flow that triggers VNF instantiation, connectivity establishment and service activation.”  This appears to define a model where functions are assembled to create a service, and then lifecycle management for each function is expected to keep the service in an operating state.  However, Service Assurance interfaces with EEO to respond to SLA failures, which seems to create the potential for multi-level responses to problems that would then have to be organized through fault correlation or response analysis.  All of that could be handled through policy definition and distribution, which Verizon’s architecture also requires.

The final interesting element in the Verizon paper is its statement on Intent-Based Networking (IBN), which is their way of talking about intent modeling and the ONF initiatives in that direction.  The paper makes it clear that Verizon sees IBN as a future approach to “populized” network control rather than as a specific principle of the current architecture, but on the other hand their models (already referenced above) seem to apply intent-based principles throughout their architecture.  It may be that Verizon is using the term “IBN” to refer only to the evolving ONF initiatives, and that it expects to use intent principles in all its model layers.

The most important thing that comes out of the Verizon document, in my view, is that neither the current ONF nor NFV ISG work is sufficient to define an architecture for the deployment of even SDN and NFV (respectively) much less for the deployment of a service.  Integration testing, product assessment, and even SDN/NFV transformation planning need to look a lot further afield to be useful, and that’s going to involve in many cases making up rules rather than identifying standards.  This means, IMHO, that Verizon is not only willing but determined to move beyond the current processes and make their own way.

For players like Ericsson, this could be good news because if every operator follows the Verizon lead and defines their own next-gen architecture, there will be considerable integration work created.  That might diminish in the long term if standards bodies and open-source initiatives start to harmonize the implementation of SDN and NFV and incorporate the required higher-level concepts.

The six vendors I’ve identified as being capable of supporting a complete NFV business case could also learn something from Verizon’s paper.  One clear lesson is that a failure to develop a total benefit picture in positioning, which I think all six vendors have been guilty of, has already exacted a price.  I don’t think operators, including Verizon, would have gone so far in self-integration if they’d had a satisfactory strategy offered in productized form.  However, all six of the key NFV vendors can make the Verizon model work.  Who makes it work best?  I think Nokia wins that one.  I know one of the key Nokia contributors to the Verizon paper, and he’s both an IMS and federation expert.  And, no matter what Verizon may feel about vCPE, it is clear to me that their broad deployment of NFV will start with mobile/5G.

Overall, Verizon’s paper proves a point I discussed yesterday—vendors who want to succeed with NFV will need to have a strong service-based story that resonates with each operator’s market, and a broad architecture that covers all the bases from operations to legacy infrastructure.  Verizon has clearly taken some steps to open up the field to include many different vendors, but most operators will have to rely on a single vendor to at least get the process started, and everyone is going to want to be that vendor.  The bar has been high for that position from the first, and it’s getting higher every day.