INVENTORIES
 6 Months Ended
Apr. 30, 2017
Inventory Disclosure [Abstract]  
INVENTORIES
INVENTORIES
As of the dates indicated, inventories are comprised of the following (in thousands):
 
April 30,
2017
 
October 31,
2016
Raw materials
$
43,905

 
$
44,644

Work-in-process
12,859

 
12,852

Finished goods
204,376

 
156,402

Deferred cost of goods sold
85,164

 
59,856

 
346,304

 
273,754

Provision for excess and obsolescence
(59,231
)
 
(62,503
)
 
$
287,073

 
$
211,251



Ciena writes down its inventory for estimated obsolescence or unmarketable inventory by an amount equal to the difference between the cost of inventory and the estimated net realizable value based on assumptions about future demand and market conditions. During the first six months of fiscal 2017, Ciena recorded a provision for excess and obsolescence of $19.6 million, primarily related to a decrease in the forecasted demand for certain Networking Platforms products. Deductions from the provision for excess and obsolete inventory relate primarily to disposal activities.