Another day, another M&A.

This time it's network security firm Fortinet with a deal to buy Meru Networks, the SDN-centric WiFi access vendor, which went public in 2010. The all-cash deal will see Fortinet pay $1.63 per Meru share for an equity value of $44 million, the companies announced Wednesday morning.

In a separate announcement Wednesday, Fortinet launched a subscription service called FortiGuard for mobile enterprise security. The company has offered WiFi access products since 2006, says Vice President of Marketing John Maddison.

Fortinet hopes that Meru, with its focus on campus networks and Open Networking Foundation (ONF)-certified SDN wireless products, will accelerate its wireless LAN business. That unit is Fortinet's "largest business outside of network security," Maddison says.

"They have a great team — Meru's engineering team is actually bigger than our whole wireless engineering team," adds Maddison.

Industry observers have considered Meru, which has struggled with flat or declining revenues in recent years, a likely candidate for acquisition. The deal comes less than two weeks after HP closed its $2.7 billion purchase of WiFi access firm Aruba Networks.

Fortinet is seen as a surprising Meru buyer, though, given the company's historic core focus on security products.

The acquisition is expected to close in the third quarter of this year. Meru stock was up 15 percent, to $1.60, in Wednesday trading. Fortinet stock, at $39.52, was roughly flat over Tuesday's close in midday trading Wednesday.