Software-Defined CPE Accelerates

SDN Adoption in Access Networks

The Move to SDNSDN, or Software-Defined Networking, is expected to be thenext fundamental change to carriers’ networks. Surveys showthat virtually all major carriers have plans to deploy SDN.What remains arguable is where carriers should deploy SDNfirst. In other words, what is the most compelling use case ofSDN in carrier networks?

SDN and CPETo answer this question, consider the driving forces behindSDN. The biggest benefit of SDN to carriers is service agility.Its centralized control and end-to-end visibility enable carriersto rapidly deploy existing services and to innovatively createnew type of services. Faster and more services equal morerevenue; therefore it makes sense to apply SDN right wherethe service begins – the Customer Premises Equipment (CPE)device.

CPE is carrier equipment in the form of a pizza box or desktopbox placed either on the customer premises or close by.Business CPE, used for enterprise and business customers, isa logical demarcation point between the carrier network andthe client network.

Note: Some carriers use other names for business CPE, suchas NID (Network Interface Device) or EAD (Ethernet AccessDevice).

SDN-enabled CPE simplifies the way that carriers managetheir access networks, which has always been a sore spot dueto the large scale of deployment and the diversity of thesupply chain. By replacing vendor-proprietary networkmanagement softwarewith common SDN controllers, carrierswill greatly simplify network operation and management,resulting in significant OPEX saving.

Figure 1 • SDN in Access Networks Enables End-to-EndControl

Software-Defined CPESoftware-defined CPE is a new class of CPE device demandedby carriers for their SDN deployments due to its inherentsupport of:

• Forwarding functions such as L2 switching, MPLSswitching or L3 routing compatible with conventionalCPE devices

• Standard southbound interfaces such as OpenFlow andOF-Config

• OpenFlow pipeline implementation of forwardingfunctions

• Flexibility to accommodate upgrades and extensions tothe OpenFlow protocol

• Carrier class features such as QoS, protection andsynchronization

With software-defined CPE, carriers can program the CPEfunction after field deployment. For example, if the CPE isdeployed in a Carrier Ethernet network, it can be programmedas a Carrier Ethernet switch. If the CPE is deployed in a PTN(packet transport network) environment, it can beprogrammedas anMPLS-TP capable switch. Software-definedCPE provides a vital element for carriers to build up the entiresoftware-defined network.

The benefits of software-defined CPE also extend to thesystem vendors who design and develop CPE devices. Today,system vendors develop protocol-specific devices such as L2switches for Ethernet networks, L3 routers for IP networks,and MPLS routers for MPLS networks. One big differenceamong these devices is the depth of the control protocol stacksupported.With SDN, the control plane software is separatedfrom the hardware device, making it possible to use simpler,protocol-independent hardware. Software-definedCPE allowsnetwork functions to be realized by running software onprotocol-independent forwarding engines. System vendorscan nowdesign and invest in a single hardware platform, thensimply develop software to turn it into various CPE products.This saving in system vendors’ development costs will alsoallow system vendors to offer their systems at a lower price,reducing carriers’ CAPEX costs.

Programmable SolutionsThe key attribute of software-defined CPE is programmability.There are multiple choices for a programmable hardwaresolution, such as CPU, FPGA or network processor. Whenselecting a programmable hardware solution forsoftware-defined CPE, there are a few importantconsiderations.

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FlexibilityNot all programmable solutions have the same flexibility.Software-defined CPE requires exceptional flexibility fromthe underlying hardware so that all forwarding functions andcarrier class features can be programmed. Usually only ageneral-purpose or network processor can offer this kind offlexibility.

SDN-friendlyThe hardware solution not only needs to be programmable,but also should comply with the OpenFlow pipeline.Essentially, the OpenFlow pipeline is based onmatch-and-action tables. A hardware solution with a similararchitecture that allows multiple iterations of lookup andprocessing in the pipeline will make it much easier toimplement software-defined CPE.

Future-proofThe OpenFlow protocol is still evolving: the ONF releases anew version every few months, with more extensions beingadded. Carrier grade OpenFlow is still under development.Ideally, software-defined CPE should evolve along with theOpenFlow standard. This is only achievable if the hardwaresolution is flexible enough to accommodate changes andadditions to the OpenFlow pipeline.

NFV (network function virtualization) enablerAdopting SDN in CPE devices is not the end game. Carriersalready have virtual CPE on the roadmap, where the CPEdevice will be capable of delivering network/IT services fromcloud servers. Some additional features become mandatoryon such virtual CPE devices in order to enable NFV, forexample security, which is necessary to protect the databetween the CPE and the cloud server. A hardware solutionwith a security engine is desirable to support futuremigrationfrom software-defined CPE to virtual CPE.

Optimized for accessLast but not least, for mass deployment, software-definedCPE must offer the same level of performance, power andcost as conventional CPE. Only hardware solutions designedand optimized for access networks will be able to deliver onthese requirements.

SummaryAdopting SDN on CPE devices in the access network willmaximize the benefits of SDN technology, so software-definedCPE is the natural choice for SDN deployment. Moreover,when choosing a hardware solution to implementsoftware-defined CPE, programmability is themost importantconsideration.

Software-defined CPE with WinPathNetwork ProcessorMicrosemi’s WinPath access network processor has anarchitecture that is fully programmable, compatible toOpenFlow’smatch-and-action pipeline, specially designed forenterprise access applications, and equipped with a securityengine, making it the perfect hardware choice forsoftware-defined CPE.

Figure 2 • Microsemi’s WinPath Solution forSoftware-defined CPE

WinPath 3Superlite

PM43594xE1 / T1

VSC85044x PHY

DDR3

SFP

Flash

SFP

OF-Config OpenFlowUNI:4xGE / GECombo

Optional:4xT1 / E1

NNI:2xGEFiber

Togetherwith turnkey third-party SDN software, theWinPathsolution provides system vendorswith an SDN-controlled CPEplatform that can be used as a Carrier Ethernet switch, a smallPTN box, or a small IP RAN router, all through softwareprogramming.

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