The head of Cisco Systems’ service provider group announced his resignation today, effective immediately.

Michelangelo “Mike” Volpi, vice president and general manager of the vendor’s Routing and Service Provider Technology group, is leaving the company he joined 13 years ago “to pursue new professional opportunities,” Cisco said.

His group, to be renamed simply “Service Provider Technology,” will be led by senior vice presidents Tony Bates and Pankaj Patel, both 10-year veterans of Cisco. The company credits Bates with having led development of its CRS-1 core router. Patel has focused most recently on high-speed broadband networks for carriers and large corporations.

Cisco will also realign certain software operations within the company to create software “expertise centers” that will integrate network operating systems into a “modular, or componentized, architecture,” Cisco said.

Volpi was considered by some to be a potential candidate to one day succeed Cisco Chief Executive Officer John Chambers. Some analysts are now speculating that Volpi’s departure better positions Chief Development Officer Charles Giancarlo--another 13-year Cisco veteran, like Volpi--to eventually become CEO.

Volpi leaves Cisco after two particularly strong quarters for its service provider business. Orders from U.S. service providers in the second fiscal quarter (which ended in January) were up by a percentage in the low 20s from a year earlier. (By comparison, orders from enterprises were up only by a single digit percentage. And commercial orders were up by a percentage in the high teens.)

Fiscal second-quarter revenue from service providers (not including Cisco’s Scientific Atlanta business) was up by a percentage in the mid teens from a year earlier. Revenue from Scientific Atlanta was up 21% from a year earlier.

Cisco reported $150 million in revenue from the CRS-1 core router in the fiscal second quarter, up 36% sequentially and up 400% from a year earlier. And optical revenue was up more than 40% from a year earlier.

“We believe Cisco is gaining market share in the [core routing] category, in addition to benefiting from continued spending by service providers on backbone networks,” UBS Investment Research wrote in a note issued this week. “Cisco has been able to validate itself as a viable service provider equipment provider over the last few years and, especially with the [Scientific Atlanta] acquisition, Cisco has deepened its relationships with the carrier community.”