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What: Shares of networking equipment maker Ciena (Nasdaq: CIEN) have popped by as much as 13% after major domestic wireless carrier AT&T (NYSE: T) abandoned its $39 billion pursuit of smaller rival T-Mobile.

So what: With the acquisition off the table, AT&T's spending budget will have some extra dollars to go around, minus the $4 billion breakup fee. Ma Bell had been cutting back on spending in order to try to push the deal through, so its presumed resumption of network buildout is seen as a positive for networking companies.

Now what: Barclays Capital analyst Jeff Kvaal had said that AT&T's mobility-related spending had dried up around September, and that equipment makers close to base station vendors would benefit most. Kvaal believes that companies like Ciena, Cisco Systems (Nasdaq: CSCO), and Juniper Networks (Nasdaq: JNPR) will benefit indirectly, since they have less direct exposure to AT&T. Ma Bell's capital spending is expected to pick up significantly starting in the first quarter of next year.

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