NetScout Systems Inc.'s first-quarter net income more than doubled as bookings increased.

The company, which sells systems that report on network performance, also announced that it purchased voice assurance technology from Accanto Systems. Financial terms were not disclosed. The transaction is expected to close this month.

NetScout earned $5 million, or 12 cents per share, in the quarter. That's up from $2.4 million, or 6 cents per share, a year ago.

Excluding stock-based compensation expense and other items, earnings were 19 cents per share.

The performance topped the 18 cents per share that analysts polled by FactSet expected.

Shares of NetScount jumped $2.21, or 11.2 percent, to $21.87 in afternoon trading. The stock has traded in a 52-week range of $10.68 to $22.49.

For the three months ended June 30, revenue climbed 21 percent to $76.4 million from $63.3 million. Product revenue increased 36 percent, while service revenue rose 7 percent.

Wall Street predicted revenue of $74.8 million.

Bookings rose 27 percent.

Sterne Agee and Leach's Alex Kurtz said in a client note that NetScout faced easier year-over-year booking comparisons this quarter.

NetScout said that the Accanto deal is expected to be neutral to its adjusted earnings for the rest of fiscal 2013 and add to its adjusted earnings in fiscal 2014 and beyond.

Kurtz was pleased with the transaction.

"The Accanto Systems acquisition today is an important move into improved voice quality assurance, an area of relative strength among some of NetScout's telecommunications focused competitors," the analyst wrote.

Kurtz reaffirmed a "Neutral" rating.

The Westford, Mass. company maintained its fiscal 2013 adjusted earnings forecast of $1.21 to $1.30 per share. Revenue is anticipated between $340 million and $355 million.

Analysts expect earnings of $1.26 per share on revenue of $347.2 million.