Rich Media Sessions: Determines the number of non-Unified Communications calls allowed on the Expressway (or Expressway cluster) at any one time. See the Call Types and Licensing section for more information.
Traversal Server: Enables the Expressway to work as a firewall traversal server.
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/expressway/admin_guide/X14-
0/exwy_b_cisco-expressway-administrator-guide/exwy_m_managing-licensing.html