arrangement consideration and revenue recognition. For those units of accounting that include more than one deliverable but are treated as a single unit of accounting, we generally recognize revenues over the delivery period. For the purposes of revenue classification of the elements that are accounted for as a single unit of accounting, we allocate revenue to the respective revenue line items within our consolidated statements of operations based on a rational and consistent methodology utilizing our best estimate of relative selling prices of such elements.

For our nonsoftware multiple-element arrangements, we allocate revenue to each element based on a selling price hierarchy at the arrangement’s inception. The selling price for each element is based upon the following selling price hierarchy: VSOE if available, third party evidence (TPE) if VSOE is not available, or estimated selling price (ESP) if neither VSOE nor TPE are available (a description as to how we determine VSOE, TPE and ESP is provided below). If a tangible hardware systems product includes software, we determine whether the tangible hardware systems product and the software work together to deliver the product’s essential functionality and, if so, the entire product is treated as a nonsoftware deliverable. The total arrangement consideration is allocated to each separate unit of accounting for each of the nonsoftware deliverables using the relative selling prices of each unit based on the aforementioned selling price hierarchy. We limit the amount of revenue recognized for delivered elements to an amount that is not contingent upon future delivery of additional products or services or meeting of any specified performance conditions.

When possible, we establish VSOE of selling price for deliverables in nonsoftware multiple-element arrangements using the price charged for a deliverable when sold separately and for software license updates and product support and hardware systems support, based on the renewal rates offered to customers. TPE is established by evaluating similar and interchangeable competitor products or services in standalone arrangements with similarly situated customers. If we are unable to determine the selling price because VSOE or TPE does not exist, we determine ESP for the purposes of allocating the arrangement by reviewing historical transactions, including transactions whereby the deliverable was sold on a standalone basis and considering several other external and internal factors including, but not limited to, pricing practices including discounting, margin objectives, competition, the geographies in which we offer our products and services, the type of customer (i.e. distributor, value added reseller, government agency and direct end user, among others) and the stage of the product lifecycle. The determination of ESP is made through consultation with and approval by our management, taking into consideration our pricing model and go-to-market strategy. As our, or our competitors’, pricing and go-to-market strategies evolve, we may modify our pricing practices in the future, which could result in changes to our determination of VSOE, TPE and ESP.