Balance Sheet Details

Accounts receivable, net consisted of the following (in thousands):



	March 31, 2018			December 31, 2017
Accounts receivable	$	56,134		$	81,793
Allowance for doubtful accounts	(388		)	(579		)
Product return reserve ⁽¹⁾	—			(822		)
	$	55,746		$	80,392


(1)	With adoption of Topic 606 on January 1, 2018, the product return reserve is considered a contract liability and has been reclassified to accrued liabilities.

Inventory consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Raw materials	$	2,244	$	1,211
Finished goods	24,817		30,318
	$	27,061	$	31,529

Property and equipment, net consisted of the following (in thousands):



	March 31, 2018			December 31, 2017
Test equipment	$	40,908		$	39,952
Computer equipment and software	33,206			32,175
Furniture and fixtures	2,744			2,714
Leasehold improvements	5,206			6,029
Total	82,064			80,870
Accumulated depreciation and amortization	(67,256		)	(65,189		)
	$	14,808		$	15,681

Accrued liabilities consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Accrued compensation and related benefits	$	18,367	$	15,563
Accrued warranty and retrofit	8,097		8,708
Accrued professional and consulting fees	5,349		9,604
Accrued restructuring charges	4,927		1,417
Accrued excess and obsolete inventory at contract manufacturers	3,371		2,430
Accrued non-income related taxes	1,604		1,778
Customer over payments	968		1,050
Product return reserve	959		—
Accrued insurance	717		827
Accrued freight	695		593
Accrued business events	—		1,272
Accrued other	3,729		6,037
	$	48,783	$	49,279

Accrued Warranty and Retrofit

The Company provides a standard warranty for its hardware products. Hardware generally has a one-, three- or five-year standard warranty from the date of shipment. Under certain circumstances, the Company also provides fixes on specifically identified performance failures for products that are outside of the standard warranty period and recognizes estimated costs related to retrofit activities upon identification of such product failures. The Company accrues for potential warranty and retrofit claims based on the Company’s historical product failure rates and historical costs incurred in correcting product failures along with other relevant information related to any specifically identified product failures. The Company’s warranty and retrofit accruals are based on estimates of losses that are probable based on information available. The adequacy of the accrual is reviewed on a periodic basis and adjusted, if necessary, based on additional information as it becomes available. Changes in the Company’s warranty and retrofit reserves in the periods as indicated were as follows (in thousands):



	Three Months Ended
	March 31, 2018			April 1, 2017
Balance at beginning of period	$	8,708		$	12,214
Provision for warranty and retrofit charged to cost of revenue	1,469			1,862
Utilization of reserve	(2,080		)	(3,298		)
Balance at end of period	$	8,097		$	10,778

Accrued Restructuring Charges

The Company adopted a restructuring plan in March 2017. This restructuring plan realigned the Company’s business, increasing its focus towards its investments in software defined access and cloud products, while reducing its expense structure in its traditional systems business. The Company began to take actions under this plan beginning in March 2017 and recognized $4.2 million of restructuring charges for the year ended December 31, 2017 consisting primarily of severance and other one-time termination benefits. Actions pursuant to this restructuring plan were complete as of December 31, 2017.

The Company established a new restructuring plan in February 2018 to further realign its business resources based on the production releases of its platform offerings. The Company incurred restructuring charges of approximately $5.3 million, consisting of primarily of severance and other termination related benefits, in the first quarter of 2018.

The following table summarizes the activities pursuant to the above restructuring plans (in thousands):



	Severance and Related Benefits			Facilities
Balance at December 31, 2017	$	975		$	442
Restructuring charges	4,567			773
Cash payments	(1,501		)	(329		)
Balance at March 31, 2018	$	4,041		$	886

Deferred revenue consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Current:
Products and services	$	10,675	$	9,125
Extended warranty	4,001		3,951
	14,676		13,076
Long-term:
Products and services	493		18
Extended warranty	20,219		20,627
	20,712		20,645
	$	35,388	$	33,721