Hassan Ahmed, who ran Sonus Networks Inc. (Nasdaq: SONS) for a tumultuous decade from 1998 to 2008, has severed his ties with the VoIP equipment vendor by resigning from the company's board.

Sonus announced Tuesday that Ahmed, who stepped down as CEO earlier this year after a lucrative 2007, "retired as a director and Chairman" on December 11. (See Ex-Moto CTO Tabbed to Run Sonus and Sonus Bonus.)

The company says it "expects to elect a new Chairman in the near future."

During his tenure at Sonus the company endured a series of financial mishaps while building up a strong position in the IP voice equipment sector. See:

Ahmed's successor as CEO, Richard Nottenburg, who has been hiring and firing to build a new senior team, now faces a number of fiscal and operational challenges of his own. See:

Nottenburg's latest appointment is Gurudutt 'Guru' Pai, who joined on December 11 as senior VP with responsibility for the company's "sales and services organizations, business development and corporate strategy functions." (See Sonus Names Guru VP.)

Pai commands an annual salary of $275,000 and "is eligible for an 'on target bonus' of 50% of his annual base salary subject to the achievement of specific objectives," according to an SEC filing. [Ed note: But does he get Ahmed's parking space?]

Pai, who joined from Web video systems specialist Veveo Inc. , has previously held executive positions at Lucent, Motorola Inc. (NYSE: MOT), and AT&T Inc. (NYSE: T).

Sonus's share price closed Monday at $1.44.

— Ray Le Maistre, International News Editor, Light Reading