Technology and telecom firms are bulking up at the fastest rate in more than a decade, new data show, driven by a continuing explosion of Internet data usage that is hitting everything from handheld gadgets to massive data centers—and the straining networks that connect them.

There have been $406 billion in deals to buy technology and telecommunications companies so far in 2015, on pace for the highest yearly total since 2000, after hitting a nearly decade-high mark last year, according to research firm Dealogic.