• Quality of Service (QoS)
  
  • Integrated Management of QoS based communication services
  • Signaling (see IETF NSIS WG)
  • QoS and mobility, esp. signaling
  • QoS mechanisms (e.g., scheduling,...)
  • Differentiated Services (you may know the lower effort PDB or multicast considerations)
  • QoS Monitoring
• Multicast
• Routing
• Scalable, efficient and stable Inter-Domain-Routing
• Intra-Domain Routing
• Multicast Routing
• QoS-Routing
• IPv6
• Policy-Based Network Management
• Scalability issues in the Internet
• Practical Security
  Applying security techniques in order to secure systems, esp. those consisting of end systems connected by a network.

• Intelligent Networks SS7/INAP
• LDAP

I also was member of the following program commitees:
LCN 2003, CCNC 2004, LCN 2004, ICC2005, LCN 2005, CCNC 2006 (HWN-RMQ Workshop), ICC 2006