Shares of Riverbed, the network infrastructure company that went public yesterday, rose 56.9 percent on their first day of trading, making it the second-best first-day IPO performance this year.

This comes despite a jittery stock market, where investors has pounded other tech companies such as Yahoo for providing disappoing forecasts, and punished other stocks broadly becausse of increasing concern about a wider economic slowdown.

The San Francisco-based Riverbed saw its shares price at $9.75, open trading at $14.60, and close the day at $15.30.

That’s good news for Riverbed’s major shareholders, which include Accel Partners, Lightspeed Venture Partners, UV Partners and Goldman Sachs.

Accel Partners and Lightspeed each own about a fifth of the company, and those stakes are valued roughly at $200 million. UV Partners owns about 10 percent, and Goldman close to 5 percent.