Riverbed Technology will acquire Opnet Technologies for about $1 billion, the two companies said Monday.

Riverbed said the acquisition will enable it to expand its network performance management business into the application performance management market.

The deal will see Riverbed pay $43 per share to Opnet shareholders, divided into $36.55 in cash and 0.2774 percent of a share of Riverbed common stock. Riverbed said the deal is expected to close by the end of this year.

"This acquisition also transforms Riverbed into a billion-dollar revenue company," Jerry Kennelly, Riverbed's chairman and CEO, said in a statement.

The announcement came as Opnet announced its earnings for the quarter from July to September. It said quarterly revenue was $47 million, a jump from $42 million in the same quarter last year.