Complex sentence: Also working with Interop at that time was Marshall Rose, who was Working Group Chair of the Internet Engineering Task Force (IETF) for the Simple Network Management Protocol (SNMP) and an outside consultant on the Interop Program Committee.
Split into simpler sentences: Also working with Interop at that time was Marshall Rose. Rose was Working Group Chair of the Internet Engineering Task Force (IETF) for the Simple Network Management Protocol (SNMP) as well as an outside consultant serving on the Interop Program Committee.