While we still don't know the details of Prodip Sen's recent career changes, we're being assured by one source close to ETSI that his stepping down from chairing the ETSI NFV effort is anything but abrupt.

Sen, formerly a Verizon executive, has been chairman of the Industry Specifications Group (ISG) that's been spearheading the development of network functions virtualization (NFV). In addition to abdicating that position, he's also left Verizon to join what sounds like a major NFV crusade brewing at HP.

The world found out about these things in rapid-fire succession, but Sen told the ISG in April that he'd be stepping down, the source says. The implication is that the transition to a new ISG chair — which will happen in late July as the ISG convenes in Santa Clara, Calif. — has been a more deliberate process than it appears from the outside, one that's being engineered with Sen's help.

Uwe Michel of Deutsche Telekom is stepping down as ISG vice-chair as well; we don't yet have many details fleshing out that situation, however. The ISG solicited candidates for chair and vice-chair last week.

Another change in the ISG ranks, although one that doesn't affect the ISG itself, is that Don Clarke has moved to CableLabs from BT. It's notable because Clarke was a big part of the initial NFV effort — he was editor of the October 2012 paper that started the while thing — and because he'd been with BT for 25 years, most recently as head of network evolution.

The ISG's charter at ETSI ends in February 2015. So, along with planning the leadership transition, the ISG has to decide what it's going to do after February, because there's strong interest in continuing the NFV effort in a formal way, possibly still under the ETSI banner.