Juniper Networks ( JNPR) is set to deliver solid Internet gear sales, but that may not be enough to overcome signs of slippage at its Net security unit.

The Sunnyvale, Calif., tech shop will present third-quarter earnings after the close Wednesday. While most investors are expecting the 12th straight quarter of better-than-expected results, some worrywarts find themselves feeling a little insecure about the security business.

Juniper has emerged as one of the few upstart success stories in the networking industry. As a top supplier to the telcos' continually strong demand for Internet infrastructure like routers, or boxes that direct data traffic, Juniper has enjoyed three years of surprising growth.

But that streak can't go on forever, say analysts. And the day the orders pace slows down, Juniper will have few places to turn to as it looks for new growth.

The $3.3 billion acquisition of network defense specialist Netscreen last year was supposed to provide a potential solution to that problem. The computer networking security outfit gave Juniper a new line of gear to sell, and a new market to sell it to.

So far though, the Netscreen investment hasn't exactly paid off. Among the setbacks have been the departure of Netscreen CEO Robert Thomas, who was expected to run Juniper's security business.

But analysts say cracking the security market and the so-called enterprise market is no easy feat, particularly for a smaller equipment company like Juniper vying with Cisco Systems ( CSCO), which controls up to 80% of some categories.

"They have some leading products, but it's a problem of how they can build on that momentum in the enterprise market," says Mark Seery, an analyst with Ovum, an industry research shop.

Seery says Juniper is at a disadvantage offering security solutions for specific points of the network when rival Cisco, with a much larger presence, takes a systemwide approach. For example, Cisco is working on a comprehensive network admission control, or NAC, that would ban traffic from devices that don't have a certain level of security clearance. That's an undertaking that would be significantly outside Juniper's reach, says Seery.

Tech spending in general has been sluggish, and that applies to all corners of the industry, it seems. In a Juniper preview report last week, UBS analyst Nikos Theodosopoulos cut his outlook on the security sector to 17% growth this year, down from 22% previously.

To be sure, though, Juniper fans will point out that security is a small part of the story for now.

Analysts are looking for Juniper to post an 18-cent-a-share profit on $531 million in sales in the third quarter. Looking ahead, Wall Street is expecting Juniper to boost its earnings to 20 cents a share on revenue of $565 million in the fourth quarter. That's a 6% sequential increase.

Juniper shares closed down 48 cents Tuesday to $21.40.

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